ERA Interim, how to handle total precipitation

First of all, these netCDF files follow the CF Metadata Conventions, which describe the use of scale_factor and add_offset in section 8.1 Packed data of the conventions description.  In short, you're applying them correctly:

  If both attributes are present, the data are scaled before the offset is added.

However, I think that you've selected the wrong fields for your purpose.  The total precipitation variable is an accumulation since the start of the re-forecast, and you've selected a monthly mean of accumulations over the first 3 hours of the 00Z re-forecasts and the same thing from the 12Z re-forecasts.  This means that you're missing the accumulated precipitation from hours 3 to 12 of the re-forecasts, so your annual mean estimates might only be 1/4 of any ballpark values you're expecting.  I suspect that you need to choose step=12 rather than step=3, as described in the ERA FAQ.

Also note, I think the comment in that FAQ about the monthly mean from daily mean data availability being "planned" but "not yet implemented" is out of date and that may be the better route to calculate the annual means (see also section 3 of Berrisford et al, 2011).


Is it possible that a reduction in vegetation is a cause of global warming?

The short answer is that people do talk about it.  It is commonly referred to as "land use change".  In general, the carbon dioxide equivalent of the effects of land-use change is on the order of 10% of the total anthropogenic contribution to CO2 emissions.  This may seem small, but it is important to realize that land-based plants are only a portion of the carbon dioxide sinks. You can see below an image from globalcarbonproject.org that shows the relationship.  See here for full presentation.


What are the cubic formations found inside Larimar gemstones?

Calcite and hematite may not be the the answer to my question

Hematite is not the answer, but calcite is.

The inclusions are not cubic, they are rhombohedral. This is precisely how calcite looks like.

  but why they stand out from the rest of the stone is beyond me.

Because calcite is a translucent mineral, and pectolite is not. You can drop some vinegar on the inclusions and you will see that they fizz a bit - this is how calcite reacts to acid.

You can read this for some more information:

http://www.openaccessjournals.siftdesk.org/articles/full-text/X-ray-Photoelectron-Spectroscopy-study.html


What makes pollen varieties useful index fossils?

Depends upon the species. If the pollen spores are large enough, and of wide spatial distribution, and easily recognizable, and preserves well in sediments, and of distinctive age range (geologically), then it could be used.

There have been mistakes in the past where modern pollen collected in microscopic pores in older rock, giving the illusion of rock ages much younger than they really are, so precautions against sample contamination are of paramount importance.


Release mechanism for methane clathrate at the PETM

There seems to be some uncertainty as to the cause and mechanism for the PETM.  In the Science Daily article Methane may be answer to 56-million-year question: Ocean could have contained enough methane to cause drastic climate change (2011) reporting research from Rice University, they claim that the seafloor was already warmer, thus according to their models:

  if the oceans were warmer, they would contain less dissolved oxygen and the kinetics for methane formation would have been faster.
  With less oxygen to consume organic matter on the way down, more sank to the ocean floor, Gu said, and there, with seafloor temperatures higher than they are today, microbes that turn organic matter into methane work faster.

Thus, they claim, the amount methane in the form of clathrates would have been approximately the same amount as today, but in a thinner stability zone.  They are not clear about what caused the destabilisation, but made the analogy of a charging-discharging capacitor (shown below, from the same source):

A recent article A seasonality trigger for carbon injection at the Paleocene–Eocene
Thermal Maximum (Eldrett et al. 2014) details of research into what vegetation eisted at the time to determine the species that were present in the time leading up to the PETM (or CIE = Carbon Isotope Excursion), they found that the seasons were already becoming warmer prior to the CIE (which led to the PETM).  The reason for the seasonal warming trend is modelled by the authors as being due to

  enhanced seasonal contrasts through Milankovitch forcing
  (Lourens et al., 2005)*, combined with a gradually warming
  late Paleocene to early Eocene, forced a non-linear response
  in ocean circulation to warm intermediate waters.

Implying that orbital influences may have had a role in causing the increased seasonal warming leading up to the CIE.

They conclude that the modelled seasonal extremes prior to the onset of the CIE

  represent the smoking gun of a climatologically forced
  threshold in the carbon cycle that caused the PETM.

Essentially by destabilising and altering the stability zone (as shown in the diagram above).

Your question about the Cretaceous raises an important point presented in the earlier article Beyond methane: Towards a theory for the Paleocene–Eocene
Thermal Maximum (Higgins and Schrag, 2006), who suggested that the carbon released from methane clathrates would not have been sufficient for the warming experienced during the PETM.

  High global sea-level
  and flooded continental interiors in the Cretaceous and
  early Tertiary may have also reduced the export of
  organic carbon from the shelves to the continental slope
  by promoting sedimentation on continental shelves that
  were 75% larger than present

suggesting that there was not enough methane clathrate, that it was 'building up' during the Cretaceous and early Palaeogene.

Astronomical pacing of late Palaeocene to early Eocene global warming events (Lourens et al. 2005) (Abstract only).


Fossil in Chert pebble picked up on a Kent beach

It a sea urchin fragment, or at least a natural mold of them. They have both the rings and the angliar joints. It is not uncommon for them to break up into clusters of those plates.


Regarding various types of atmospheric pollution

As a USA resident, the EPA is the best place to start when wondering about the emissions inventory of atmospheric pollutants or pollutant precursors that affect the National Ambient Air Quality Standards (e.g. Particulate Matter, Carbon Monoxide, Sulfur Dioxide, Lead, Nitrogen Oxides, Volatile Organic Compounds).  The EPA compiles a comprehensive emissions inventory of all criteria pollutants at the county level which is available in the National Emissions Inventory (compiled once every 3 years).  You can see the summary of your county at http://www.epa.gov/air/emissions/where.htm.  As for the effects of atmospheric pollution, it is important to consider the lifetime of said pollutants in the atmosphere in order to put their environmental impacts into perspective.  For instance, the air pollutants covered by the National Ambient Air Quality Standards have immediate health effects when high concentrations are breathed in regularly.  Both animals and plants are adversely affected by these irritating and sometimes toxic chemicals, but these pollutants are also reactive and do not last long in the atmosphere unless they are constantly being replenished (e.g. daily traffic).  Air quality also impacts critical nitrogen loads on ecosystems and possible production of acid rain.
If you are interested in Greenhouse Gases (e.g. methane, carbon dioxide, CFCs, nitrous oxide), the EPA has a separate site for those emissions since they are not part of the same regulatory framework  http://www.epa.gov/climatechange/ghgemissions/ .  Greenhouse gases typically do not cause adverse health effects for plants or animals on land.  However, they have long-term radiative effects (e.g. the greenhouse effect) because they stay in the atmosphere for many years and trap infrared light.  These long-term radiative effects are what can change climate and consequently land cover.  Furthermore, most of the excess carbon is absorbed by the ocean, which creates carbonic acid. Increased acidity of the ocean causes severe problems for marine ecosystems.
The EPA states that in 2012 the CO2 equivalent GHG emissions for the USA by sector was:

Electricity production (32% of 2012 greenhouse gas emissions) - Electricity production generates the largest share of greenhouse gas emissions. Over 70% of our electricity comes from burning fossil fuels, mostly coal and natural gas.
Transportation (28% of 2012 greenhouse gas emissions) - Greenhouse gas emissions from transportation primarily come from burning fossil fuel for our cars, trucks, ships, trains, and planes. Over 90% of the fuel used for transportation is petroleum based, which includes gasoline and diesel.
Industry (20% of 2012 greenhouse gas emissions) - Greenhouse gas emissions from industry primarily come from burning fossil fuels for energy as well as greenhouse gas emissions from certain chemical reactions necessary to produce goods from raw materials.
Commercial and Residential (10% of 2012 greenhouse gas emissions) - Greenhouse gas emissions from businesses and homes arise primarily from fossil fuels burned for heat, the use of certain products that contain greenhouse gases, and the handling of waste.
Agriculture (10% of 2012 greenhouse gas emissions) - Greenhouse gas emissions from agriculture come from livestock such as cows, agricultural soils, and rice production.
Land Use and Forestry (offset of 15% of 2012 greenhouse gas emissions) - Land areas can act as a sink (absorbing CO2 from the atmosphere) or a source of greenhouse gas emissions. In the United States, since 1990, managed forests and other lands have absorbed more CO2 from the atmosphere than they emit.

If we consider GHGs on a global level (see Global Carbon Project http://www.globalcarbonproject.org/carbonbudget/index.htm ) we can see how each sector has impacted the atmospheric concentration of CO2 over the past 143 yrs.


For any of the basic forecast runs (10 day, ensembles, monthly/seasonal forecasts), I do not believe ECMWF data access is general controlled to ECMWF.INT.  Generally most data, including anywhere near enough to use in a WRF forecast, is only available for purchase at extreme fees (generally we're talking 5+ figures per year).  The only option you might have is if you are doing your modeling for strictly research purposes, in which case you may qualify for a research license at reduced or free cost, or be able to access it from servers at the institution you are associated with.

It does appear that reanalysis data and various other specialized products are available free with an account at their website as described here.  I believe reanalysis would only get you initial conditions which I don't believe is sufficient to run a mesoscale model like WRF(?), and that they are also poorer quality/resolution (please correct me if I'm wrong on any of these beliefs!!)  Archived actual ECMWF output is still pay (see the bottom option on the license page).

I worked with ECM for a few years while producing content at StormVistaWxModels and definitely indeed found most things with them to be quite a challenge, limitation, and pity!  At the time it was fairly abstruse to find what you needed or communicate with them, though it appears to have improved some.


A massif is an undisturbed solid rock mass, which is demarcated by e.g. faults. Massifs keep their internal structure and are displaced as a whole. Only mountains of mountain ranges fulfilling this criteria are called massifs.


Dataset for expected sea level rise in case of massive meltdowns (Greenland/Antarctica)

You should try to use the equations and maps presented by Mitrovica et al., (2011), entitled On the robustness of predictions of sea level fingerprints.  In this paper they present the history of sea level rise equations and then present their own robust equation with comparisons.  There are maps showing the differences as well.  Soon they will provide fortran code so that you can try it out yourself, which will be published here.


Relationship between natural disaster and global warming, in the media

First thing first: It is very hard, if not impossible, to attribute a single anomalous weather event to climate change. The weather exhibits a huge amount of natural variation.

The recent spate of cold weather that recently has hit the eastern part of North America is consistent with climate change and has even predicted to be a consequence of climate change. However, this spate of cold weather is also completely consistent with natural variations in the weather. As noted above, it's very hard to attribute a single weather anomaly to climate change. Winter weather is, by its nature, extremely variable.

It's also important to remember that this cold weather is a local event. Europe and Asia have been quite balmy this winter. Do not be surprised if December and January turn out to be considerably warmer than historical values when averaged over the entered planet. And even if it isn't, that does not falsify climate change. Climate change is about what happens after removing short term variations ("years" is short term) from the equation.

Note that I have been consistently using the term climate change rather than global warming. It's not that global warming is an incorrect term. People mistakenly take global warming to mean that every single day will be warmer than it was a year ago, everywhere on the planet. The science does not say this. As noted above, the recent spate of cold weather that has plagued and continues to plague eastern North America is completely consistent with and has been predicted by climate change (or global warming, if you will). But it's also consistent with natural variations.

That said, at least one event during the last year most likely was amplified by climate change, and that would be the huge amount of water dumped on southeast Texas by Hurricane Harvey. Tropical cyclones (e.g. hurricanes) and even very strong ones, are natural occurrences. Climate change does not predict that we will get more tropical cyclones. It does however predict that they will get more severe as the Earth warms up, on average. The huge amounts of water dumped by Harvey are consistent with and predicted by climate change, but not so much consistent with natural variations. While Harvey itself wasn't caused by climate change, a sizable portion of the 52 inches of the rain that it dumped most likely was a result of climate change.

Update, since I didn't directly address the questions raised

One reason I didn't address those questions is because the original post has too many questions (Martin: Please read up on how to write a good stackexchange question.) I'll focus on a couple of them.

  On average, is the media doing a fair and balanced job as an educator of under-informed people (like myself) on that topic?

The first of the cited reports in the question has the teaser headline "Flooding in Paris Maybe Due To Climate Change" -- but the link does not discuss that at all. The news report merely covers the fact that Paris is currently flooding. (Perhaps a once longer version did cover a potential link to climate change.) This is a disservice because a potential link between flooding in Paris and climate change does exist. In particular, climate change has roughly doubled the probability of severe flooding events in Paris.

The second cited article is much better. It does not attribute the late December / early January cold snap in the US to climate change. It merely states facts. One fact is that many people (including the president of the US) see a cold snap as falsifying climate change. Another fact is that this is not the case. Climate change, aka global warming, does not say that winter will vanish. (Okay, some alarmists do say that. You need to ignore them, along with the deniers.) The natural variations in winter weather in temperate climates is huge. Climate change has not overcome these huge swings. We will continue to see cold snaps.

  Are they providing an even and science-based account of the relationship between natural disaster and global warming, honestly explaining how global warming is a complex phenomenon which may have surprisingly different --- and sometimes maybe “counter-intuitive” for lay people --- impacts here and there (including cooling and increased likelihood of sever weather in some areas)?

This depends very much on where one gets ones news on climate change issues. Fox News? The odds are against it. According to one study, 72% of Fox News's reporting on climate change was inaccurate or downright false, with the inaccuracies veering toward denialism. This same study found MSNBC to do a much better job, with only 8% of its reporting on climate change being inaccurate or downright false (with the inaccuracies here being mostly overly alarmist).

That said, an 8% error rate is nothing to write home about, and the superficial nature of the reporting is even less to write home about. The news media is not where you should go if you want good reporting on climate change, or on science and technology in general. I have a rather low regard for news media journalism regarding science and technology. The reporting is rather awful. Keep in mind: Journalists in general avoided STEM classes from the ninth grade and up, and when they couldn't, they took classes like Physics for Poets.


Are there any other sites that allow users to search for historic hurricanes within a given area?

There is this atlas for the North Indian Ocean basin - Indian Ocean Cyclone Atlas and while I am not sure about the cyclone tracks for the pre satellite era cyclones the site is comprehensive and covers all cyclones in the Indian Ocean up to the current period. After you register yourself here - Registration  then you can view the cyclone tracks.

Here is a sample of cyclone tracks between 2012 and 2016


Coal self-heating and spontaneous combustion, how does this happen?

Sulphur/sulphides in coal may be one of the causes of self combustion.

A slight diversion - in some metal sulphide mines, such as copper, at high level of sulphides in the ore, the sulphides can oxidize thus creating sulphide fires. If a lot of dry dust is produced during stope blasts, during the mining process, sometimes the  sulphide dust can cause a secondary, unwanted, explosion.

Most coal deposits contain sulphides/sulphur. Most lignite (brown coal, also low quality or low grade coal) deposits are nearer the surface, thus if lignite has lots of sulphur & it oxidizes with atmospheric oxygen combustion can occur.


How does the ozone layer "stay in place"?

For the ozone layer to dissolve, it would need something to bind to. Chloroflurocarbons are one very notable thing that it can bind to, but that doesn't exactly answer the question.
While the ozone layer would be 3 mm thick if it was compressed down to the pressure of earth's surface, since it is further up in the atmosphere, it can take up a larger volume (like 20 km thick). The ozone layer is maintained by the Chapman cycle.
That is, the oxygen molecule ($\ce{O_2}$) is dissociated by UV radiation (photolysis) to oxygen atoms ($\ce{2O}$). Then the photolyzed oxygen atoms ($\ce{2O}$) can bond with two oxygen molecules ($\ce{2O_2}$) to make an two ozone molecules ($\ce{2O_3}$), provided another molecule can take away some excess energy.
Since it is a cycle, there has to be a way for the ozone to return to oxygen. One ozone molecule ($\ce{O_3}$) can photolyze to make an oxygen atom ($\ce{O}$) and oxygen molecule ($\ce{O_2}$). The oxygen atom ($\ce{O}$) can react with another ozone molecule ($\ce{O_3}$) to make two oxygen molecules ($\ce{2O_2}$).
To just answer your question directly, the ozone layer is replenished by the sun's UV energy reacting with the oxygen in the atmosphere.


Are average daily temperatures affected by DST?

They compensate for DST.

That is, for any daily measurement, they use the same universal time every day of the year.  If they take a measurement at 7:00 local time in summer, they will take the same measurement at 6:00 in winter.

(So if you do see a DST effect in the data, that would be due to traffic and other local anthropogenic effects shifting by an hour relative to the time of measurement!  Perhaps due to urban heat island effect, or forcing by anthropogenic aerosols from traffic or industry.)


Identifying thrust faults on a geologic map

Geological maps are the interpretation by a number of geologists and are generally the synthesis of extensive field work. The only place with the real evidence is the field (including geophysical work and drillholes, if available obviously). In many countries geological maps are accompanied with a guide discussing certain interpretations, especially regarding faults, which are quite often up for discussion. Maybe you can find the author of the map and ask them if such a guide is available, or even directly ask on what base the fault was drawn? I think you'd find many geologists willing to discuss their interpretation.
Other indications ("evidence" is a bit strong) for thrust faults can include an unexpected contact between two layers, a sudden change in orientation and/or thickness of the layer(s).
If you're really sceptical, try to sketch a small geological profile and see if you can make a different interpretation.


Looks like cone from cone in cone limestone, a uncommon texture of limestone rock.
It is most likely not a fossil.

I have found very similar pieces here in Ohio that are Cambrian age.

An accurate description of cone in cone limestone can be found at:
https://en.wikipedia.org/wiki/Cone-in-cone_structures

Also, I have found a number of fossil teeth from fish, sharks and mammals over the years and teeth are most often not the same color as the rock they are found in.


I suggest you consider the concept of radiative forcing. It is the net change in energy balance at the top of the atmosphere due to imposed perturbation. The change in radiative forcing is a function of multiples of factors: water vapor, solar radiation, anthropogenic and natural emissions of CO$_{2}$, etc. So, attempting to quantify future temperature to a single forcing may not be a good way of relating the two vars. You may consider running climate models that consider the above factors.
However, you can play around with single var relation you suggested. I can proved an alternative derivation that considers radiative forcing.
The relation between temperature perturbation and radiative forcing is
$$\Delta T = \lambda RF$$
where $\lambda$ is the climate sensitivity parameter and RF is a radiative forcing due to a particular perturbation.

The above equation can be re-written,
$$T - T_{o} = \lambda RF $$
where $T_{o}$ is a particular reference temperature. You can take base period temperature (e.g., 1980 to 2015).

Assuming temperature increases steadily in time, $T=T_{o}e^{ct}$, and inserting into the above equation,

$$T=\lambda RF (\frac{1}{1-e^{-ct}})$$
 Now you have $\lambda $ and  RF as coefficients.


TRMM rainfall measurement for synoptic systems

The Tropical Rainfall Measuring Mission (TRMM) satellite is a single satellite, carrying multiple instruments on board, as described here. It makes a total of 16 orbits/day at a low altitude of 400 km, with different swath widths for each instrument. Thus, the measurement product that you get is not a "continuous" measurement of a single atmospheric phenomenon, but a composite of multiple orbital passes and instruments, where the density of coverage will depend on the time period over which the composite is made.

If you take a look at TRMM data access page, there are 3 levels of data, each level depending on the amount of processing and quality control:

Level 1: Precipitation radar (PR) reflectivity
Level 2: Combined rainfall profile - PR + Microwave interferometer (TMI)
Level 3: 3-hourly composite of the above + additional data from other instruments (satellites, ground measurements, ground radars), with extended range to 60S - 60N.

Level 1 and 2 data are nearly raw, and are not composites - they give you data from all 16 orbits/day, and each swath cross-section along the orbit will have a timestamp associated with it. Level 3 data will be the most spatially "continuous" of the three, but one must be aware that this is a composite of multiple orbital swaths and multiple instruments, so it is more suitable for slowly evolving (larger scale) systems.

Related: Is there a database of global rainfall time series?


What type of minerals exist in this rock?

It is massive white quartz also referred to as milky quartz, the streaks are  trace impurities and can occasionally include valuable metals like gold but just as often included fools gold (pyrite).

This chat can help with more detailed identification of trace metals https://www.mindat.org/mesg-11-219962.html


Why is the pressure on the poles higher in Summer and lower in Winter?

My answer will only relate to the question in the title: Why is pressure on the poles higher in summer and lower in winter?

Due to the axis tilt of the earth the winter hemisphere gets less heated by solar radiation. This leads to a high temperature gradient from equator to the winter hemisphere pole (strong baroclinicity). In contrast we have a low temperature gradient from equator to the summer hemisphere pole.
The missing solar heating in the winter hemisphere additionally leads to descending air at the pole leading to low pressure at jet stream level (around 300 hPa). On a non rotating planet the air would of course directly flow from the high pressure (equator) to the low pressure (pole) to remove the pressure gradient. As warm air would flow to the cold pole air, this would also weaken the temperature gradient. But due to the rotation of the earth, air flows around the area of low pressure. This flow gets increasingly stronger as the meridional temperature gradient strengthens.

This maybe seen from thermal wind balance, which tells us that the geostrophic wind $V_g$ is related to the temperature gradient $\nabla T$ by
$\frac{\partial V_g}{\partial \ln p} = -\frac{R}{f}k \times \nabla T$.
Here $p$ is pressure, $R$ is the gas constant for dry air, $f$ is the Coriolis parameter and $k$ is vertical unit vector. Assuming there is no zonal temperature gradient, we can conclude that a strong meridional temperature gradient leads to an increasing change of $V_g$ with height. We can observe this strong wind as the strong/weak jet stream in the winter/summer hemisphere. What does all of this have to with the pressure?

The jet stream acts as a barrier, dividing the warm and cold air masses. The Temperature will keep getting lower which will also increase the pressure and temperature gradient. In return the barrier (jet stream) gets stronger. This positive feedback mechanism remains until after winter solstice. Then the radiation reaching the pole will increase again, warming the air masses. Which will then lead to a weakening of the gradients.

So summarizing the above one could say, the missing radiation cools the air leading to a low pressure system at jet stream level. The jet stream itself gets stronger as the temperature gradient increases and acts as a barrier for warm and cold air masses and therefore maintains the pressure difference.


How to map emission inventory from lat&lon corrdinate to WRF model grid

I would suggest using cdo for your purpose. At least for variables, which values are independent of the grid cell size, one can use cdo.

cdo

cdo (Climate Data Operators) is a command line program to process netCDF and GRIB files. It is developed an maintained by Uwe Schulzweida and colleagues at the Max-Planck Institute for Meteorology in Hamburg, Germany.

cdo Homepage
cdo HTML Manual
cdo Forum

cdo provides different operators to process your data. You can chain several operators in one command. You always start with the call of cdo. Examples:

cdo OPERATOR1 -OPERATOR2 -OPERATOR3 inputfile1.nc inputfile2.nc outputfile.nc
cdo OPERATOR1 -OPERATOR2 inputfile1.nc -OPERATOR3 inputfile2.nc outputfile.nc

The first operator is just appended to cdo. All further appended operators need to have - as suffix.

example

Assume, we have two files (file1.nc and file2.nc) with some ocean data (sst, salinity, u, v, ...). We want to calculate the difference between the sst of both files. This is done via

cdo diff -selname,sst file1.nc -selname,sst file2.nc outfile.nc

We could do this also in four steps:

cdo selname,sst file1.nc sst_of_file1.nc
cdo selname,sst file2.nc sst_of_file2.nc
cdo diff sst_of_file1.nc sst_of_file2.nc outfile.nc

Interpolate data with cdo without considering grid cell size

cdo provides different operators for interpolation. REMAPBIL for bilinear interpolat, REMAPNN for nearest-neighbor interpolation, and so on. They are listed in the manual. I use remapbil here as an example.

cdo remapbil,NEW_GRID_DEF file_old_grid.nc file_new_grid.nc

The file_old_grid.nc is your input file and file_new_grid.nc is your output file. Here you find an example from my work at GitHub:

cdo remapbil example

The grid definition on your input file file_old_grid.nc needs to be recognized by cdo. To test, whether it is recognized you can try

cdo griddes file_old_grid.nc

If it prints out the correct grid definition, then everything is fine. If not, you need to correct the definition of your lon-lat grid. Please have a look in the respective section below for details.

The NEW_GRID_DEF is a file, in which the target grid is described. If your target grid is a nicely defined grid, you can write this file by hand. E.g. it could look like (copied from the HTML manual of cdo):

gridtype = lonlat
xsize    =   60
ysize    =   30
xfirst   = -177
xinc     =    6
yfirst   =  -87
yinc     =    6

Please look for "CDO grid" and "grid description" in the cdo HTML Manual to fine more examples and explanation on it.

If you don't have a nicely defined grid, you can generate your NEW_GRID_DEF. This is, what I have often done, because our chemistry transport model setup needed a non-nicely defined grid.

cdo griddes file_with_wrf_grid_definition.nc > NEW_GRID_DEF

In file_with_wrf_grid_definition.nc, the model grid has to be defined and it needs to be recognized by cdo. Here you find an example from my work at GitHub:

cdo make grid definition

How to make cdo recognize

cdo assumes that your file conforms with the CF Conventions (Climate and Forecast Conventions). Please have a look in the respective chapter of the CF Conventions Document to get a general description.

A working grid definition could look as follows (as ncdump output):

dimensions:
  time = UNLIMITED ; // (1 currently)
  lay = 1 ;
  lat = 78 ;
  lon = 62 ;
variables:
  float lat(lat, lon) ;
          lat:long_name = "latitudes       " ;
          lat:units = "degree north    " ;
          lat:var_desc = "latitude (south negative)                                                       " ;
          lat:cell_methods = "TSTEP, LAY: mean" ;
  float lon(lat, lon) ;
          lon:long_name = "longitudes      " ;
          lon:units = "degree east     " ;
          lon:var_desc = "longitude (west negative)                                                       " ;
          lon:cell_methods = "TSTEP, LAY: mean" ;
  float DATA_VAR(time, lay, lat, lon) ;
          DATA_VAR:long_name = "some long var name" ;
          DATA_VAR:units = "some unit" ;
          DATA_VAR:var_desc = "some description" ;
          DATA_VAR:coordinates = "lat lon" ;

The important aspect is that the data variable has an attribute coordinates, which value contains the two lon and lat dimensional variables (I attached a second example so that it becomes clear). Additionally, the standard_name and units attributes should be properly set at the dimensional variables.

dimensions:
  time = UNLIMITED ; // (1 currently)
  lay = 1 ;
  lat = 78 ;
  lon = 62 ;
variables:
  float lat_1(lat, lon) ;
          lat_1:long_name = "latitudes       " ;
          lat_1:standard_name = "latitudes       " ;
          lat_1:units = "degree north    " ;
          lat_1:var_desc = "latitude (south negative)                                                       " ;
  float lon_1(lat, lon) ;
          lon_1:long_name = "longitudes      " ;
          lon_1:standard_name = "longitudes      " ;
          lon_1:units = "degree east     " ;
          lon_1:var_desc = "longitude (west negative)                                                       " ;
  float DATA_VAR(time, lay, lat, lon) ;
          DATA_VAR:long_name = "some long var name" ;
          DATA_VAR:standard_name = "the standard name" ;
          DATA_VAR:units = "some unit" ;
          DATA_VAR:var_desc = "some description" ;
          DATA_VAR:coordinates = "lat_1 lon_1" ;

Interpolate data with cdo with considering grid cell size

No idea how it works with cdo


Freely available and re-distributable weather observations over the US?

Such a dataset can be found via the NCDC. Here is the main gateway. My 'go to' place for high temporal resolution data from NCDC is the 5-minute ASOS data.


How is the difference in crust and mantle composition explained?

Generally speaking , Earth interior is classified using two models , the mechanical and chemical model . the chemical model layers are crust , mantle and core. these layers organized while earth started to cool after formation at the stage known as planetary differentiation . heavier materials like Fe And Ni sunk to the core , while the lighter materials like Al and Si stayed at the outer surface of the ball .
Read more about Planetary differentiation if you are interested


Is there enough water to cover the surface of a topographically normalized earth?

Here is a very simplistic approximation:
The total volume of the oceans (no lakes, rivers, water vapor) is around $1.3\ 10^9$ cubic kilometers. The surface area of Earth is around $5\ 10^8$ square kilometers. Dividing the volume by the area, we get a depth of 2.5 kilometers. The fresh water contribution is about 3% of the volume of salt water.

In reality, other factors such as the fact that Earth is not spherical, density changes, and that the water will be acted upon by tidal forces and other interactions, will make the distribution uneven.


What is the total Earth's interior energy budget?

If you see wikipedia here:
en.wikipedia.org/wiki/Earth's_internal_heat_budget

They have a nice summary of the answer I think you are looking for:

  The flow of heat from Earth's interior to the surface is estimated at 47 terawatts and comes from two main sources, the radiogenic heat produced by the radioactive decay of isotopes in the mantle and crust and the primordial heat left over from the formation of the Earth. Earth's internal heat powers most geological processes and drives plate tectonics. Despite its geological significance, this heat energy coming from Earth's interior is actually only 0.03% of Earth's total energy budget at the surface, which is dominated by 173,000 TW of incoming solar radiation.

You can divide by the surface area of the Earth to get your rate per square meter.


How do we measure the total heat content contained in ocean and atmosphere?

The heat content of a substance is known as enthalpy.  The international convention used for the Thermodynamic Equation of Sea Water is maintained by the Joint Committee on the Properties of Seawater.

Equations for calculating the thermodynamic variables of sea water, humid air and other substances are set forth in the Numerical implementation and oceanographic application of the thermodynamic potentials of liquid water, water vapour, ice, seawater and humid air – Part 1: Background and equations by R. Feistel, D. G. Wright,†, D. R. Jackett, K. Miyagawa, J. H. Reissmann, W. Wagner, U. Overhoff, C. Guder
,A. Feistel, and G. M. Marion. Enthalpy of sea water is discussed in section 4.3.

One would need temperature, pressure and salinity information for each point in the ocean, and integrate specific enthalpy over the entire volume of the ocean.


Probability ( weather tomorrow = weather today)?

As mentioned, the term you are looking for is persistence.  Generally its strength varies wildly depending on what variable you are looking at, the location, and by whether you also further select other factors like season and other meteorological variables.

I would expect daily precipitation persistence is a relatively bad predictor, given that precipitation is often either a short-term event driven by very transient dynamics like frontal passage, or sees a fairly random spatial distribution over small areas driven by small perturbations and nonlinear interactions (thus typically leading to rain PoPs regularly being more useful than binary forecasts).

Persistence is often used as a basis to compute forecast skill... but it seems to be be reported in research using more sophisticated summarization metrics like skill scores than straight probabilities.

However, with a little searching I did at least find A Markov Chain Model for the Probability of Precipitation Occurrence in Intervals of Various Length by James E. Caskey, Jr., which did at least have a table along the lines you've asked... for Denver, Colorado between 1949-1958, using 0.01" (0.254 mm) as the condition:

For those struggling to figure the values out, in this table when $\rho_1$ is similar to $r_1$, utility of precipitation persistence is low.

Colorado is a mountainous area, so I could imagine large-scale wind direction aloft probably proves more significant than many areas.  For a location like Florida in the summer or Oklahoma in the spring, I'd imagine the skill is lower as persisting variables are less important.  Still, because humidity often varies more slowly, regularly controlled by air masses and large scale wind directions, which often are directed by large synoptic weather features, there will likely be at least some difference in the conditional probabilities in all locations/seasons.

Don't know if that data is useful enough for your lecture purposes, but hopefully it offers a branch to seek into.  You may be able to dig up a few more similar tables by searching on through research journal results in places like the AMS or, if need and desire be, could calculate such variables from station data available at sites like NCEI.


What is the metamorphic field gradient useful for?

You are entirely correct. Todd and Engi write:

  The mineral assemblages of rocks at the surface lie on a locus of
  P–T-conditions… It must be stressed…does not imply a P–T-distribution or geotherm realized at any one time during the orogenic evolution of this area. Even assuming the P–T-values
  reflect maximum metamorphic conditions, these were established at
  different times in different areas…show the integrated effect of all
  the tectonometamorphic processes…i.e. the sum of burial, heating,
  tectonic and erosional unroofing and cooling.

Notwithstanding, the metamorphic field gradient is still useful, particularly when comparing different sets of rocks.

Each of the samples in your figure (A, B and C) is a single rock and looking at it tells you the history of this rock and this rock alone. When studying a large area (a "field") there will be many rocks, that may differ from each other in their individual P–T-path. For example, in a rock suite that is now dipping 90°, one might argue that walking 3 kilometres on the surface equals 1 kbar of pressure, equals about 3 kilometres of depth. Because of that, each sample along the transect will have experienced different temperatures, with ideally the deeper ones also being the hotter ones.

By choosing a convenient reference point (maximum temperature of an individual sample), and connecting all samples along a transect, you can get an estimate of a P–T gradient, which can approximate a geotherm (under many assumptions). The same Todd and Engi paper has this figure:

Each of the lines is based on several dozens of individual samples. Based on this representation of the data, they go on to conclude:

  The metamorphic field gradients and age determinations and consistent
  with two stages of metamorphism. The first stage created the field
  gradients preserved in the northern part of the field area. The second
  thermal pulse affected only the south-eastern part of the field area.
  This occurred at a later time, under lower pressure conditions.

Reaching those conclusions is only possible when condensing the 100 or so individual samples they used (i.e. 100 individual P–T-path loops) to what turned out to be only two metamorphic field gradients.

Todd, C. S. and Engi, M. (1997), Metamorphic field gradients in the Central Alps. Journal of Metamorphic Geology, 15: 513-530. doi:10.1111/j.1525-1314.1997.00038.x


Considering the thin piece of material on the surface of Mars in the image below, is there anything like it on Earth?

What you can see in the bottom picture is sandstone/mudstone/claystone.

If you look at the bottom picture top right you can see a thin rock that has split off, this is how a rock splits after it has been heated and then suddenly gets cooled down as it does on Mars when the Sun goes down.

On Earth the change in temperature is too slow for this to happen in nature, but you can see this if a fire has been burning on top of a rock/stone and it has been rapidly cooled down.

This is how mining was done before explosives where invented, heating up the rock until it is "glowing" hot and then throwing water on the rock to suddenly cool it down so it fractures.


Why do the Siberian methane craters have smooth vertical walls?

Permafrost is defined as

  a ground, or medium, (including rocks, soils and organic matter) with a mean annual temperature less than 0 °C for at least 2 consecutive years.

The smooth appearance of the walls can be explained by understanding how permafrost works. Permafrost is characterized by an active layer, which is a layer normally at the surface which freeze yearly during winter and thaw during summer - this layer at Yamal can be 1-2 m deep depending on the local ground characteristics (snow depth, albedo, slope, air temperature, thermal conductivity, runoff etc).  The ground in the area is ice-rich.

Then let's assume this crater was caused by a methane bubble escaping/exploding and walls could be rough immediately following the event. By deduction, there should not be an active layer found on the walls following the explosion, as it is the first time this ground (walls) were exposed to air. During the middle of the summer, above 0°C air enters the hole due to convection. The ground is ice-rich (can be porous or invisible ice but still ice-rich) and active-layer start to form on the wall.

Due to the near vertical orientation of the walls, saturated soil (or active layer in formation) cannot stand because as soon as it thaw to a depth exceeding its equilibrium limit, it fall at the bottom of the crater due to gravitational forces, exposing a new frozen surface (and the cycle continue until equilibrium can take a few years). Thawing sediments in ice-rich soils can reach saturation quickly, further adding to the weight and accelerating the time of the fall. Rugged and unequal surface are typically the first elements to thaw and fall.

I took this picture about an hundred km from the featured crater.

This display a very ice-rich section of the Yamal Peninsula littoral in the course of erosion. This coastal section has been eroding for decades at least. At the top the active layer is light brown, and look dry (1 m deep). Just under this top-layer, the ice is poly-genetic: ice wedge ice-rich soil and massive ice can be seen as well. The active layer cannot stand on the side for the reasons I exposed in the previous paragraph (gravity).

Side-note, the jagged edges were not initiated by anything related to a pingo. It takes decades, up to many centuries for a pingo to develop until its natural collapse. When it happen, a depression can form at its center - which could lead to a lake, but these are not overnight processes. Also, contours of the pingo mound would not appear as jagged edges if this was a pingo - the remains would appear pretty old and vegetated, alike the surrounding countryside.


3 Billion years ago, the earth is covered with Carbon Dioxide. Where did it go?

It went into:

Limestone

Mostly made out of calcium carbonate (CaCO3)

Coal

Oil and gas

Living biomass

Subducted into the mantle

Occasionally coming back as diamonds

Or as volcanic gas

All images public domain from here


Can I go to forests, national parks or mineral deposits and mine

I think the basic answer to this question is No, or rather, not without the land owners permission.

For example it is illegal to remove pebbles from a beach: Woman who 'stole' pebbles from a BEACH to decorate in her garden given police warning

For more information on mineral ownership in the UK see: Legislation & policy: mineral ownership


Heating and cooling a non-magnetic iron ore causes it to become magnetic?

What's happening is called induced magnetism, detailed in a variety of places, including this paper by Kostadinova-Avramova and Kovacheva in Geophysical Journal International:

  It is well established that baked clays, when cooling from
  temperatures around 700 °C in a weak magnetic field, such as that of
  the Earth, acquire a thermoremanent magnetization (TRM) that is
  related to the direction and intensity of that field.

When materials are heated above their Curie temperature -- which varies based on the material -- they lose any permanent magnetic properties they had. As the material cools below its Curie temperature, its magnetic particles are influenced by the local magnetic field and the material develops a new, parallel magnetic structure in response.

So your ferrous clay could be picking up a magnetic field from the Earth, from a local electromagnetic field generated by your kiln or other electrical sources, or even a sufficiently strong local magnetic source.

This mechanism is sufficiently well understood that the field of paleomagnetism studies ancient fired clay objects and other materials of known dates to determine the strength of Earth's magnetic field in a given era and region.

History of Earth’s magnetic field exposed in Judean pottery explores one such application of the process:

  In a new study published in Proceedings of the National Academy of
  Sciences (PNAS), researchers from Tel Aviv University, Hebrew
  University of Jerusalem and University of California-San Diego cite
  data obtained from the analysis of 67 well-dated Judean jar handles.

  These heat-impacted ceramic pots, which bear royal stamp impressions
  from the eighth to second centuries BCE, show evidence of changes in
  the strength of the geomagnetic field over the years.

  “The period spanned by the jars allowed us to procure data on the
  Earth’s magnetic field during that time — the Iron Age through the
  Hellenistic Period in Judea,” said Erez Ben-Yosef of TAU’s Institute
  of Archaeology, the study’s lead investigator.


Why is Paris still polluted during the Covid-19 shutdown?

There are fewer cars. Are they only a small part of Paris' air
  pollution?

Recent evolution of European standard on emissions for private vehicle means that the average car is polluting orders of magnitude less than the average gasoline-burning heater.

Even for a city plagued by the widespread use of huge, inefficent cars (New York), the heating systems (heat and hot water) may account for >40% of the emissions https://blogs.ei.columbia.edu/2019/01/15/heat-pumps-home-heating/

A couple of emissions pie-charts for PM10 and PM2.5 for Paris in 2012 (from the report Inventaire régional des émissions en Ile-de-France Année de référence 2012 - éléments synthétiques Edition mai 2016 )

and


The seriousness of global warming/ climate change?

Try asking Pacific Islanders that question.  Most Pacific islands are only a few meters above sea. Some have already had their fresh water sources, destroyed by rising sea levels. Most of these people are in danger of losing the land beneath their feet & becoming environmental refugees.

Then there is Bangladesh, a low lying country, without any hard rock, where gravel is made by baking clay. It already is losing significant parts of the country to coastal erosion, some of which was farmland.

If you're not concerned about Pacific islanders or Bangladeshis, then how about Europeans? Significant portions of the Netherlands are already below sea level, sustained by a system of dykes and sea walls. Some of theses are in danger of being overwhelmed by rising oceans and the land being lost.

If you're not concerned about Europeans, then how about Americans? Will Americans want to pay for system of sea walls to protect New Orleans? It already has issues trying to build a wall along its border with Mexico, but that's another issue.

Rising sea levels will inundate land with salty sea water and it cause the lose of softer coastal terrain to erosion, such as limestone cliff terrain in Britain.

The other thing that rarely gets mentioned is the affect that lost coastal habitats, such as mangroves, will have on non-human life. As if human life is the only form of life that matters on the planet and that nature is irrelevant. Humans need nature more than nature needs humans. Some of these habitats are critical to the some fish species and other life forms.


About four kilometers, see, for example:
http://www.mbgnet.net/salt/oceans/data.htm
But bear in mind that much of the oceans, especially in the southern hemisphere, have scarcely been mapped at all, so it is currently impossible to give an accurate estimate.


The forecasts issued by the National Hurricane Center are made by people. Those people use every single tool they have at hand. This includes forecasts made by automated tools such as the European Centre for Medium-Range Weather Forecasts (the "European model"). It also includes forecasts made by several other models. The human-generated forecasts account for the skills of those various models, for the ages of the forecasts made by those models, and for data that are not used by those models.

When multiple models more or less agree, the human forecasters use techniques and their judgement to split the difference. There is no splitting the difference when models disagree massively, as currently is the case with Jose. The current forecast (advisory 20A at 0800 AST on 10 September 2017), depicted graphically below, appears to be exactly that made by the ECMRWF.


Redrawn after Zachos et al. 2001.

This is a plot of the Cenozoic variations of $\delta\ce{^{18}O}_{Cibicidoides}$ according to Zachos et al. 2001 (this is a bit outdated now but the Paleocene is roughly the same in more modern curves such as Zachos et al. 2008 or Cramer et al. 2011). It is supposed to follow variations in deep ocean temperatures and thus reflect the climate state at a given time. The Paleocene is the timeframe delimited by the two vertical bars (you can see the PETM quite clearly on one of the two bars).
From that plot it seems the Paleocene deep-sea temperature prior to the PETM is roughly at the same level at it is during the Middle Eocene (ca. 45 Ma), i. e. warmer than most of the Cenozoic but colder than the Early Eocene or most of the Cretaceous.
There isn't actually that many studies focussing on the Paleocene itself, this is clearly a time interval that is studied so far mostly because of the K/T boundary or the PETM, i. e either because of its start or its end.


First, inhomogeneities in the ocean are in fact quite common. There are density gradients in both horizontal and vertical directions and those gradients result in the baroclinic circulation of the ocean. The density gradients in the ocean are caused by salinity and temperature differences.

Rossby waves are common in the ocean. They propagate along lines of latitude with the waves traveling along the Equator being the most obvious example and the most thoroughly studied. As in the case of atmospheric Rossby waves, their formation and propagation is related to the conservation of (potential) vorticity (rotational movement, angular momentum). A parcel of water has two sources of vorticity: its own spin and the planetary spin. When a parcel of water moves across a latitudinal line, its planetary spin (planetary vorticity) changes (as the Coriolis effect is latitudinally dependent) and, in order to conserve vorticity, it changes its own spin (relative vorticity). The water parcel tends to swing back and forth around the original latitude resulting in a wave-like motion. A Rossby wave is characterized by a westward phase velocity (that of the wave crests).


How much Sulfur Dioxide is emitted into the atmosphere from a mine fire?

All coal deposits are different. Coal chemist is highly varied, and the amounts of sulfur and heavy metals with the coal seams varies with each deposit & within seams. This is due to the conditions prevalent when the coal seams were formed.

Consequently, the amount of sulfur dioxide emitted when coal is burned, whether in a power station or a mine fire depends on the amount of sulfur in the deposit the coal came from.

Without having an assay of the amount of sulfur in the coal or measuring how much sulfur dioxide is generated in a fire it is impossible to know how much sulfur dioxide will be produced.


Do trees capture more CO2 during a fast growth stage?

Right, there are a lot of misconceptions about this. They are mostly to do with the difference between the magnitude of carbon storage and the rate of carbon uptake, and also the difference between whole site carbon storage and above ground biomass carbon storage. There is also ongoing research taking place which (as you might imagine) takes a very long time because of the life expectancy of most tree species.

The standard forester's response is: a hectare of new forest will tend to grow on a Sigmoid / logistic curve (well described by Paine et al. 2011) which looks like this:

This is based on an even aged stand (so, multiple trees, planted at the same time).

Interpreting this, we can see that the greatest rate of carbon uptake is between years 25 and 75 (for this site, species, etc.) but the greatest level of carbon storage is not really achieved until year 150+. You can read more about this in the infamous "Blue Book" by  Forest Research.

Based on this alone, we would assume that mature forests do not sequester much more additional carbon per ha per year, but they do store a lot more than if we simply felled the forest to maximise carbon uptake. However...

1) Below ground carbon (soil carbon, roots, stumps etc.) doesn't follow the same rules. Carbon can remain sequestered in soils (particularly peat) for very long periods and can continue to be laid down (depending on site conditions) more or less indefinitely. When soils are disturbed (for example by felling operations or drainage) they release carbon. So any forest disturbance will tend to release soil carbon.

2) It doesn't scale well to individual trees as pointed out in in Stephenson et al. (2014). This is because the total tree population per ha is of a variable size (tree mortality and thinning means that there are fewer trees per ha over time).

This means we end up with a trade off between storing the carbon we have already sequestered and drawing down new carbon into the system. The degree to which the carbon sequestration rate decreases over time depends a lot on the forest soil, climate, species, and other local conditions. There is an academic discussion taking place over the difference between a simple measurement of above ground woody biomass (as shown above) and a whole-site carbon balance.

It can get quite complicated, and how you look at it can result in different results. Do you definitely want to model individual trees? Or are you thinking about forests in general?

Hope this helps.


Do Pyroelectric gemstones really exist? Can they be found on web market?

Yes, pyroelectric gems exist. No, they don't produce electricity all the time. Pyroelectric gems can generate a certain amount of electric potential when cooled or heated.

To cite Wikipedia

  The change in temperature modifies the positions of the atoms slightly within the crystal structure, such that the polarization of the material changes. This polarization change gives rise to a voltage across the crystal. If the temperature stays constant at its new value, the pyroelectric voltage gradually disappears due to leakage current (the leakage can be due to electrons moving through the crystal, ions moving through the air, or current leaking through a voltmeter attached across the crystal)

A full list of all piezoelectric minerals can be found at the website of the Mineralogical Society of America

And yes, you can buy them. Some, like Axinite, were used to remove hair and lint from objects.

There's no site like www.buypiezoelectricgems.com... So you should google them one by one and look for sellers. Or go to a gem fair.


The problem with the cancelling you suggested is that it is imposed globally for the PDE and not locally (just on the thin layer).

Usually when we talk about vertically layered media we use a plane wave $\exp(i(\mathbf{k}\cdot\mathbf{x}-wt))$ trial solution (you can plug this in to confirm that it satisfies the PDE) and match boundary conditions at the interface of two layers to determine reflection and transmission coefficients. If you are not familiar with this, Aki and Richards (1980) is a good reference. See also the Zoeppritz equations https://en.wikipedia.org/wiki/Zoeppritz_equations

Introducing a very thin, stiff layer is equivalent to placing a 0 displacement (Dirichlet) boundary condition at the location of the layer. Physically, this models an infinite impedance reflector and will generate a total reflection. Waves on a string with both ends fixed are modeled in the same way.

Setting vertical derivatives in displacement to 0 is imposing a Neumann B.C. on the location of the thin layer. This is exactly how the free surface is modeled. Physically, this models vanishing vertical tractions at the boundary location.

So, if you want to model seismic wave propagation with an extremely stiff layer, then use the Dirichelet 0 displacement boundary condition. If the thin layer is only 'very stiff', use the reflection and transmission coefficients provided by the Zoeppritz equations. If you want tractions to disappear, use the Neumann boundary conditions. But, beware; this doesn't make physical sense if the thin layer is sandwiched between two other layers.

Hope this helps.
-D


How can we have groundwater depletion when the Earth is 78% covered with oceans?

How can we still lack groundwater?

That 71% of the Earth's surface is covered by oceans is completely irrelevant to the issue of fresh groundwater depletion. Salty groundwater is useless for drinking or irrigating crops.

The issue at hand is the depletion of those underground reserves of fresh water. This depletion can result from natural or human causes. The Sahara is an example of natural depletion. The Sahara was significantly wetter than it is now several thousands of years ago. Rains over the course of a few thousand years created a number of underground reservoirs of fresh water in the Sahara. Rain stopped falling on the Sahara about 7000 years ago. The few remaining oases in the Sahara are places where groundwater still comes close to the surface as a result of that roughly 3000 year long wet spell.

Humans can also cause groundwater depletion. It takes several centuries for rainfall to percolate down to the water table. The replenishment of aquifers is very slow. This is balanced by a very slow trickle from a natural spring here, another one there. The end result is a more or less steady state where the slow replenishment balances the slow outflow. It's very easy to disrupt that balance. Climate change (both natural and anthropogenic) can change the replenishment rate, while artificial wells can drastically increase the depletion rate.


Why do P waves have a higher velocity in the lower mantle than in the core even though the core has a much higher density?

tldr; Increased density corresponds with decreased P-wave velocity

The P-wave velocity for an isotropic medium is:

$$
V_p = \sqrt\frac{K+4/3\mu}{\rho}
$$

where $K$ is the Bulk Modulus, $\mu$ is the shear modulus, and $\rho$ is the density (https://en.wikipedia.org/wiki/Elastic_modulus, see $M$ the P-wave modulus). Isotropy just means that the strain on the rock caused by a stress is irrespective of the stress orientation. Examining the equation you can see that increased density corresponds with decreased velocity.

In the mantle, $\rho$ increases with depth, but the numerator $K+4/3\mu$ increases faster than the $\rho$, so the net effect is an increase in velocity.

In the fluid outer core, $\mu = 0$. This is because fluids do not support shear stresses. Correspondingly, $V_p$ drops precipitously.

In the solid inner core, $\mu$ is nonzero hence there is a jump in velocity at the inner/outer core boundary. The combination of $K$, $\mu$, and $\rho$ in the inner core is such that $V_p$ doesn't exceed the lower mantle values.


Is seismology really the only way to measure the thickness of Earth's layers?

Robert Mallet is sometimes referred to as the "father of seismology." He was helped (around 1850) by the newly created science of photography, which enabled him to create seismic "maps" of the earth, at different depths.

He has started life as an iron engineer/manufacturer, but turned his talents to seismology after a number of devastating earthquakes in Europe. His earlier work with iron gave him a background in the use of explosives to "open up" the earth at critical points.

Paleoseismology is a related field that relies on paleontology to form estimates of various properties of the earth.


Not all sediments are deposited in water, but water is important in the formation of most sedimentary rocks.

If we're just thinking about the deposition of the sediment, then we don't necessarily need water. Some counterexamples are:

Aeolian sandstones, such as the Lower Permian Rotliegend sandstone of the North Sea. These are deposited by wind, not water.
Some types of sedimentary breccia, which are chiefly deposited by gravity, not water.
Tuff, which are deposited by gravity and wind, not water. They also undergo substantial compaction and lithification with or without water.

But deposited sediment does not a rock make. Once deposited and if buried, most sediment undergoes compaction and diagenesis, eventually lithifying — a fancy word for turning into a rock. Below the water table, the shallow crust is saturated with (mostly) saline water, and processes like dissolution and cementation are necessarily aqueous. So it's fair to say that water is essential in the formation of sedimentary rocks, on Earth anyway.

Footnote

You were right to be skeptical, by the way; the video is introductory material apparently intended for grade school audience, so you can't treat it like a textbook. And you can't even take a textbook as 'truth', especially when it comes to slippery things like definitions. Sometimes generalizations and simplifications help, sometimes they don't.


Does over-cropping large areas really change the amount of rainfall?

For an example of how bad agricultural practices can cause soil loss and end up with dust and sand, see the conditions that preceded the dust bowl in the USA.  Certain crops are bad for soil and if not rotated will eventually deplete the soil of nutrients leading to no crops.  With nothing holding the soil in place (roots) it will erode. The Sahara has other ill effects going on, such as synoptic scale atmospheric descent (interaction from the Walker Circulation and the Hadley cell) which promotes dry, warm conditions.

I'm not sure that rainfall will vary based on soil health, but one avenue to look into is soil moisture and other sources of water.  Rain begins as water vapor and that water vapor comes from evaporation (from bodies of water, entrainment), evapotranspiration (from soil and plants) and advection (blown in with the wind).  If the predominant flow does not bring in moisture and you lose the ability to hold water in the soil, this could conceivably locally reduce water vapor mixing ratios and impact precipitation.  That is just a guess and it would be worth searching the literature (you can freely download AMS articles older than 2 years old and search them here).


What you saw was a crepuscular ray. They occur when the Sun's rays stream through gaps in clouds. Such rays tend to appear as parallel columns.

If you look closely at the picture you took, there is a subtle angled crepuscular column above the short building near the middle of the picture.


What woud happen to me if I touched the aurora?

The lowest reaches of an aurora is ~100 km in the air.  Your problem won't be the ionized gas, it'll be that the air pressure is close to zero.  Also, aurora are very diffuse, with at most a few glowing molecules per square centimeter.  I'm not sure at that density that you could tell you were actually in something.

If you're in a spacesuit to survive the lack of oxygen, you might worry about the high-energy electrons that sometimes make it through to those altitudes, but fundamentally your problem is that you won't really be "touching the aurora" because you're in a space-suit and you can't really see that you're in it.


I don't know who voted down your question. I'm guessing those who voted it down thought that prior to asking your question you could have searched on the internet to find out how the Sun and the solar system, including Earth formed.

I've just found the following two links by doing just that. The following quote is from one of them and it explains the current theory/model for the formation of the solar system:

From Birth of the Earth

  Long, long ago (some 5 billion years ago) in a perfectly ordinary place in the galaxy, a supernova exploded, pushing a lot of its heavy-element wreckage into a nearby cloud of hydrogen gas and interstellar dust. The mixture grew hot and compressed under its own gravity, and at its center a new star began to form. Around it swirled a disk of the same material, which grew white-hot from the great compressive forces. That new star became our Sun, and the glowing disk gave rise to Earth and its sister planets. We can see just this sort of thing happening elsewhere in the universe.

Read this article from Wikipedia as well.

https://en.wikipedia.org/wiki/Formation_and_evolution_of_the_Solar_System#Formation_of_planets


Will global warming expand the tropical zone

It depends on how you define the tropics. Strictly speaking, the tropics can be defined as the area between the tropic of capricorn and the tropic of cancer (23.5$^\circ$N/S respectively). This is because of the earth's axial tilt of 23.5$^\circ$. Since I don't think that the climate change will affect the axial tilt too much, I doubt it.
However, if you define the tropics in terms of climate, probably. Since the Hadley cell is expected to expand with more greenhouse gases, it follows that the tropical weather that accompanies the Hadley cell should expand with it.


Regarding car exhaust and its possible carcinogenic effects

Yes almost definitely. Its not just gas, but additives, lubricants/oils, coatings, coolant (some of which leaks into the combustion chamber) etc. The full list of known carcinogens is available here.

Also see the EPA report here which says ...

"EPA estimates that mobile (car, truck, and bus) sources of air toxics account for as much as half of all cancers attributed to outdoor sources of air toxics. This estimate is not based on actual cancer cases, but on models that predict the maximum number of cancers that could be expected from current levels of
exposure to mobile source emissions."


In the 800 kyr $\ce{CO_2}$ record, how detectable would a short-term peak be?

$\small\mathsf{CO_2}$ does not fall back quickly:

  graph shows the IPCC 2007 $\small\mathsf{CO_2}$ liftime from a computer model run that shows what happens to a single instantaneous pulse of $\small\mathsf{CO_2}$ emitted to the atmosphere. One thousand years after the $\small\mathsf{CO_2}$ is emitted to the atmosphere 20% is still there according to this model.
  only zero carbon

The decline shown is mostly due to $\small\mathsf{CO_2}$ dissolving in the oceans.


Current consensus on the Messinian Salinity Crisis

According to palaeoclimatic records modelled from sediments studied at Monte dei Corvi, in the paper Reconstructing the temperature and salinity of the Mediterranean Sea through the Late Miocene (13 Ma - 6 Ma) prior to the Messinian Salinity Crisis (Alexandrina et al. 2014), that using alkenone paleothermometry, there was a cooling trend starting at 8.1 million years ago, developing a cold period around 7 million years ago and continuing to the Messinian Salinity Crisis (MSC) as evidenced by a disruption in marine sedimentation (and changes to the surrounded flora and desertification in the Sahara).

Research presented in the paper The Onset of the Messinian Salinity Crisis along the offshore Betic Range (Ochoa et al. 2014) suggest that tectonic processes along the offshore Betic Range in southern Spain may be a trigger for the closure (see tectonic map below for the relevant area).

Image source: Wikipedia

The MSCis described in the paper Modelling global-scale climate impacts of the late Miocene Messinian Salinity Crisis (Ivanovic et al. 2014) as being the result of the influences of climatic change as observed in sedimentary strata described by Alexandrina et al. 2014 and of tectonic activity of the offshore Betic range, as detailed by Ochoa et al. 2014.  They also suggest that during the MSC, there were intermittent outflows of saline water into the Atlantic - causing disruptions to the thermohaline circulation.

Dr. Iuliana Vasiliev of the University of Utrecht, suggests that one possible influence during the MSC was interactions with the closing remnants of the Paratheys Ocean, as shown in the map below:


How do optical satellites detect different leaf types?

Short answer

Different plants reflect light at different wavelengths with specific patterns. If you know the reflection pattern of a broad-leaved forest and that of a needle-leaved forest, you can compare them with the pattern observed with a satellite and conclude to which forest it is more similar.

Long answer

Optical remote sensing

Optical sensors record electromagnetic radiation at different wavelengths between 400 and 2400 nanometers. This radiation came from the sun and impacting surfaces of different materials on Earth surface is either absorbed by, transmitted through or scattered back. The amount of radiation that is scattered back is then detected and recorded by an Earth-Observing sensor such as MERIS', MODIS' or Landsat's. Due to chemical and physical properties of different materials, they can absorb, transmit and reflect different proportions of radiation at each wavelength. The reflectance recorded by a sensor for a pure material is called spectral signature. This signature is often unique for a material. This can help identify the presence of different materials on the Earth surface when a spectral signature is known.

In the laboratory, with more sophisticated and accurate sensors, is possible to identify the spectral pattern of single pure chemical compounds or molecules. However, if we scale up and consider the spectral response of a whole forest, you can easily imagine how everything gets mixed up: the spectral signature of many pure molecules in different proportions, scattered back and forth in more or less dense and geometrically various canopies are all sensed by a single sensor unit (for example, one pixel of our satellite image).

Estimating the presence and amount of different materials on the heterogeneous Earth surface becomes a very complex problem and researchers have found many a method to partially overcome it and obtain reasonably accurate estimations of what covers Earth surface and in which amount.
Predominantly, 1) the observed mixed spectral response of a material is statistically linked to in situ measurements, or 2) the spectral response of mixed materials is simulated with computational models and is statistically compared with the observed one.

In both cases, it is possible to use the whole spectral signature or specific metrics derived from specific regions of the spectrum, that we know are related to the presence of some substance that is related to what we are trying to describe.

The spectral properties of plants

The spectral properties of plants have received quite the interest in the past 50 years and one undeniable spectral feature that all green vegetation has, that substantially differentiates it from that of soils, rocks, artificial materials and water is the so-called red-edge. The red-edge is characterised by a low reflectance in the visible radiation (due to chlorophyll absorption) and a high reflectance in the near infrared region.

The Normalised Difference Vegetation Index (NDVI) is one of the many metrics proposed to quantify the red-edge feature. The index is very simple and needs only two bands and no site-specific adjusting constants:

NDVI = (Red-NIR)/(Red+NIR)
Red = reflectance of the red radiation
NIR = reflectance of the near infrared radiation

Since its simplicity, the NDVI is probably the single most used index in optical remote sensing of the vegetation.

The NDVI is a metric for the red-edge feature and thus it is influenced by chlorophyll activity and the presence of other vegetative tissues. And it was successfully (empirically) related to the phenologic stage, plant health, biomass and leaf area index.

In conclusion, if you know the expected spectral signature of a pine forest and that of an oak forest, you can compare them with the spectral signature of any pixel you observe and estimate to which forest the pixel's spectral signature is the most similar.

Clearly, the NDVI can be used for that comparison rather than the whole signature due to its simplicity and versatility; additionally, its interannual patterns can differentiate between annual and perennial, and evergreen and deciduous forests.

However, depending on the resolution of the sensor and the scope of the project, more metrics are possible and different classification methods become available.
There are several other features that have been identified in plant spectral response. For example, the lignin, starch, cellulose and water absorption features in the short wave infrared.

If you have a look at the image below, you can notice that even the age between needles is differentiable by the spectral signature detected by very high spectral resolution sensors. Such sensors are typically handheld while satellite sensors commonly have between 5 and 15 points where you see a continuous line below.

Image from: Rautiainen, M., Lukeš, P., Homolová, L., Hovi, A., Pisek, J., & Mõttus, M. (2018). Spectral Properties of Coniferous Forests: A Review of In Situ and Laboratory Measurements. Remote Sensing, 10


Found an article that used a simple analytical modelling to determine how high a mountain can be. Reference

Based on simple physics, tallest a mountain will be on Earth is ~10 km.
This is based on:

Simple cone shape for the mountain. Vol ≈ $r^2 h$
Based on weight of the mountain:  Weight W ≈ $\rho g r^2 h$
Stress σ the mountain exerts on the ground underneath it is:

σ ≈ Weight/Area ≈ $(\rho g r^2 h)/r^2$ ≈ $\rho g h$
The limiting factor is the compressive strength of the rock:
Assume granite with an average density $ρ$ = 3 g/cm$^3$.
Compressive strength is $\sigma_C$ = 200 MPa = $2 \times 10^8\, N/m^2$
Stress = Compressive strength of rock  σ = $\sigma_C$ or $\rho g h_{max} = \sigma_C$.
Calculate max height:

$h_{max}$ ≈ $\sigma_C/(\rho g)$

$h_{max}$ ≈ $\frac{2 \times 10^8\, N/m^2}{3 \times 10^3 kg/m^3 \times 10\, m/s^2)}$≈ $10^4\, m$ = 10 km


Would the Earth function the same spinning the other way?

That would have many consequences. For example the Coriolis force would change the sign. Thus wind around pressure systems would switch the direction from north and south hemisphere, but also the Ekman spiral in the ocean would be affected. Surface heating at sloped terrain will different, as the sun would rise in the West. This would change thermal induced circulations. And the conservation of angular momentum is important for the general circulation.

I would expect major impacts on the resulting climate, even in an equilibrium mode, which does not account for the acceleration to the oppose rotation velocity.

During the time of stopped rotation additional circulation systems can be expected, which exchange energy between the day and the night side of the earth.


Why air do not suffer density stratification of its gaseous components?

So, naively, one would expect the heavier gasses to pool in the lower atmosphere and the light ones at the top.

That's overly naive. That same naive expectation would lead one to think that uranium should be concentrated in the Earth's core, or that a mix of water and ethanol should be differentiated with water on the bottom and ethanol on top. Uranium is instead concentrated in the Earth's crust, and water and ethanol readily mix. Entropy and chemistry can lead to counterintuitive results.

That most certainly is the case with gases. The entropically-favored distribution is a thorough mix. Attaining this thorough mix can take a long time if only molecular diffusion is in play. Turbulent mixing makes the mixing proceed much more rapidly.

There are places where this entropically-favored distribution does not occur. Gases can be concentrated in mines and in basements. For example, mines have problems with concentrations of methane and carbon monoxide (both less dense than air), but also with concentrations of carbon dioxide and sulfur sulfide (both more dense than air). Basements in areas with lots of granite have problems with radon (significantly more dense than air). Gases can concentrate in mines and basements due to a diminished turbulent mixing. This enables processes that produce gases to overwhelm the slow molecular dispersion process, resulting in an entropically-disfavors distribution.

The Earth's upper atmosphere is also differentiated. Here, the extreme rarity of the upper atmosphere means that turbulent mixing is highly attenuated. Extreme solar radiation (high UV and x-rays) produces gases by splitting molecular oxygen, water vapor, and to a lesser extent, nitrogen, into constituent parts. The very long mean free path in the upper atmosphere means that the lighter components move higher than do the heavier components.


Why does Earth have two kinds of crusts?

First they do get slowly mixed at the plate boundaries but the mixing is minimal compared to the amount of crust there is. They do not mix easily since they have different densities, they tend to separate out when melted so most mixing is done in their solid states.

An easy way to think of it is there is not enough continental crust to cover the entire planet so oceanic crust is filling in the gaps. A better analogy is to think of continental crust as scum on pond (or foam in a tub). The uppermost portion of the mantle and oceanic crust are basically the same thing, oceanic crust is just colder, while continental crust is different in composition it is lighter and floats on top but as I said there is not enough of it to cover the entire planet so like scum on a pond it forms clumps and gets pushed around by the underlying currents. And just like pond scum they separate out because they have different densities than the "water" so they collect on the surface.


The United States Geological survey might have some data on soil
As should the US Dept of Agriculture.
More to it, Universities with Agriculture departments


There are a couple of possibilities, depending on what you're paying the most attention to.  This falls in an overlap area of terms that vary from region to region and even from person to person.

The key thing to notice in your photo is the whitish band running along the top of the escarpment that borders your landform.  This shows that it's held up by a resistant, mostly horizontal, layer of sedimentary rock.

This French page refers to it as a cuesta; this is plausible, but the strata underlying cuestas usually slope more than what appears in your picture.

(generalized cuesta image from Wikipedia)

"Plateau" is also plausible, but this is not very specific. The landform in your picture doesn't have quite the extent of the Colorado Plateau.

Tableland or table is probably the most generic name for the entire regional structure under the rock layer.

If you are talking about the remnant under the pin in your image (and especially if this were in America),  then we'd have no trouble calling it a mesa or even a  butte.

(Wikipedia image of a mesa in Monument Valley)


How to calculate cumulative moment magnitude?

The moment magnitude ${\displaystyle M_{\mathrm {w} }}$  is a dimensionless number defined by Hiroo Kanamori as:

$$M_{\mathrm {w} }={\frac {2}{3}}\log _{10}(M_{0})-10.7$$

To sum several moment magnitudes we need to first convert them to  ${\displaystyle M_{\mathrm {0} }}$ (seismic moment) which you can simply sum and then convert it back

for each of the magnitudes you have - insert the magnitude into ${\displaystyle M_{\mathrm {w} }}$, solve for ${\displaystyle M_{\mathrm {0} }}$ and write down the answer.
Sum all the answers
Insert the sum back into ${\displaystyle M_{\mathrm {0} }}$ and solve for ${\displaystyle M_{\mathrm {w} }}$


Himalayas are currently rising. What will be the highest point they can reach?

The Himalayas are indeed rising, but they are also being eroded at a comparable rate. It will come as no surprise to anyone that the maximum possible height of a mountain on Earth is only marginally higher than Mt Everest, that is probably about 9000 to 10,000 metres high. There are, of course compressive / convergent plate boundaries where there is a potential  tendencey to build higher mountains, but non-linear counter processes kick in to counteract the mountain building. There are three processes, glacial erosion, shear collapse and lower crust / upper mantle plasticity. The latter is the most important. As lateral compression builds higher mountains, the mountain roots are depressed into the hot plastic region such that the mountain literally sinks under its own weight, deforming the root zone, sometimes in spectacular fashion. Go to Scotland, or Norway, where you can see the eroded remains of the long-gone Caledonides, and you can see the exposed and metamorphosed root zone of mountains that were once as big as the Himalayas.

In principle, the mountain would eventually collapse by shear failure, simply because the rock isn't strong enough to support the weight of gigantic mountains. In practice, deformation takes place before the shear failure is reached.

Then there are glaciers. The higher the mountain gets, the more rain  turns to snow, then to ice, which is a phenomenally effective erosive agent (just look at any of the worlds recently glaciated terrains - European Alps, Patagonian Alps, Norway, Alaska, New Zealand, etc., to see the spectacular erosion). This erosion peaks at a high altitude, but not at the very highest altitude, where the atmosphere is so cold that it cannot deliver much moisture - so very little snow. Result: glacial erosion takes bites out of the mountain at middle-upper elevations, thereby keeping the slopes steep, whence gravity collapse along pressure release joints, and other related processes. Hence occasional peaks get close to 9000 metres but, in geological terms, they don't last long before erosion brings them down.


Are there any other earthquake magnitude scales other than Richter's?

Earthquakes are measured for intensity and magnitude. Magnitude and intensity are related but measure very different properties of the event. Magnitude is the energy released of the earthquake. It is determined from measurements. Intensity is determined from effects on buildings, landscape and people. Naturally an earthquake with high magnitude would also generate high intensity, but the intensity depends on distance from the hypocenter and the local geological conditions.

Modified Mercalli Intensity scale is a way to rate the intensity of an earthquake, but the scale ends at XII (Damage total), not at 13-14 (XIII-XIV), as mentioned. China seismic intensity scale (CSIS), Medvedev–Sponheuer–Karnik scale and European macroseismic scale can reach values above ten, but not 13-14. XII on the Medvedev–Sponheuer–Karnik scale is Very catastrophic and IX in Destructive.
Medvedev–Sponheuer–Karnik scale is used in some Asian and European countries,  Russia, India, Israel etc. CSIS is used in mainland China.

Magnitude is also measured in different scales. Related to the Richter's scale is the Moment magnitude scale, it's an updated better way to measure, but it usually produce similar values as the old Richter's scale and the two scales are often confused in media. There are few other scales, Body wave magnitude, surface wave magnitude, but to my knowledge they also stay under 10.

Some of the confusion might come from that the Richter scale is logarithmic. A difference in magnitude of 2.0 is equivalent to a factor of 1000. An earthquake measured to 9.0 is one million times stronger than an earthquake at 5.0.


I think the reason you were marked wrong is because your text book is using the term "climate" loosely.  The deterioration of vegetation will result in desert encroachment ... which in turn can cause a change in local climate.  After all, if you create more desert, you have changed the local climate, right?  However, it takes many years to define a climate period, whereas desert encroachment can happen year to year.  So, eventually the local climate can change... but not if the desert encroachment reverses for some reason.  It's a very fine line, but answer #1 will most certainly occur while #2 may occur afterward if #1 is sustained.


I am afraid that you aren't being specific enough to really answer your question: What about mountain chians valleys and hills are you interested in? There are simple and complex models dating back from the 1960s to present. Are you interested in learning about the material properties of the crust, or just topography in general? What about weathering effects? What about the flow laws that govern the lower and middle crust (depending on who you talk to).

I would look into the field of dynamic topography and how that is calculated.

Two books that I think might be useful to read are Fowler and Tourcotte and Schubert, they will help give you an overview of geodynamics as a field, and what engineering solutions we apply to Earth. In the 1-D and 2-D flow sections there is much about the crust.

A good starting paper might be Bird 1991 (sorry, its probably behind a pay wall, but I couldn't find an open pdf on it).

As far as codes (and consquently mathematics) The two sections of CIG I would look at are S-T Dynamics and Mantle Convection.

I am sorry I couldn't provide a comprehensive answer, but I think the sources I've linked may give you a good start and thinking about this problem.


What caused a measurable patch of Mt. St. Helens' ash to be deposited across Oklahoma?

I will propose an explanation. From experience I would say it have something to do with the US meteorological systems (systems as in masses of air) active the 18th of May 1980 and the week(s) after.

A bit of background : air masses can be high pressure (cool, and stable) or low pressure (warmer, more energy, more volatile, less stable). The next figure show in red a low unstable and warm system, and in blue a cool, stable system. (full website here)

Further, let's take into account the meteorological nature of Oklahoma - as an area in a volatile sector, where warm wet air masses from the gulf collide with colder, dryer masses from the west and the north - area part of what is broadly know as the tornado alley. On the wiki page for OK we see a typical system condition favorable for volatile weather. Green masses are warm, blue are cold and red is where the action is likely to occur.

Tornado or other frequent wild weather events are the result of a clash between those widely different air masses, temperature, moisture and pressures often leading to storm cells or other unpleasant windy/stormy situations.

Now let's get back to our volcano. I found those daily meteorological maps from the NOAA. When entering the proper dates, let's say 18th of May 1980 and the week after, we see the various systems in action. To keep things simple, I picked the 18th of May, and  the 21st.

The 18th of May there was a low pressure system about right over the volcano - which was ideal to transport and displace a lot of ashes very far. The 20th, at 7:00 am, there was a Low in formation over Oklahoma which would become full fledged the 21st (see figure) and there was bad weather that day over Oklahoma City because of clashing cell. Eventually causing precipitation (rain and ash?).

I am not a climate-meteo-specialist, but I have good confidence that this scenario could explain a part of the reason why there is ash in Oklahoma.


Which greenhouse gas does the most damage to crops?

Tropospheric ozone is a significant greenhouse gas (see e.g. IPCC AR4) and has well established negative effects on crop yields. For example, Van Dingen et al (2009) evaluated yield losses of up to about 15% globally, depending on the crop.


lets say a water company do deliver water to a city but as the city expands the water source are no longer able to keep up with the demand so the water company have to drill a new well,This is now an alternative source for water the company will still use the primary source for water but will need to use the secondary source in periods of high water demand.

The same is true for building materials if the primary supplier are not able to deliver what you need,You have to get it from an alternative source.

And as i mention in my comment,my primary supplier of electric power is hydro power,So this is the primary source of power for me and if i use more power than they can produce the rest must be supplied from an alternative source,Here this will be wind power or import from other sources.

In denmark the primary source for electric power is wind and the secondary sources is hydro power from norway or coal power from the continental europe.

the comment from fred is an answer to this question too


Estimating the residence time of atmospheric CO2 from bomb 14C

Judging by the general quality of the first graph, I don't think that it is the most reliable source. However as I don't feel like reading trough all papers, I will accept the numbers as they are stated. However once you include uncertainties of the observed residence time, I would assume most of the studies are not significantly different from each other.

The variability in the calculated residence time can be due various reasons; the measurement location, the number of observations used and the length of  the observational record.

The measurement location is probably the most important source of variation as results may vary a lot depending on where you measure. Multiple observation locations measuring what is called background air masses would be needed to get a good indication of the global average residence time of $CO_2$ in the atmosphere.

I would say you are spot on with the complicating factors.
Local influences are important as $CO_2$ emissions have different radiocarbon signatures depending on their origin. $CO_2$ from fossil fuel burning contains no radiocarbon while the nuclear industry emits low amounts of pure $^{14}C$ (not necessarily in the form of $^{14}CO_2$ though). The natural sources and sinks of $CO_2$ (biosphere and ocean) are also not in equilibrium with the atmosphere since the atomic bomb tests in 1950s and 1960s. Immediately after the bomb tests, the large amount of $^{14}C$ produced in the atmosphere meant that it was enhanced in  $^{14}CO_2$ compared to the biosphere and the ocean. Since then, $^{14}CO_2$ has decreased in the atmosphere, as it was taken up by the biosphere ant the oceans. This lead to an such a large increase in  $^{14}C$  in the biosphere and the surface ocean, that they are now enhanced compared to the atmosphere.

This graph including the oceans should explain what I mean.


Are 'Return Periods' being recalculated? If so, how?

One possible example could be the study of ice cores in Antarctica where scientists are trying to determine changes in concentrations of gases like carbon dioxide over a period of time . Such variations serve as indicators for other Climate related factors such as Temperature.

This record was a key contribution to climate science. One, it revealed how past CO2 levels compared to past temperatures. And since the data was directly derived from air bubbles trapped beneath hundreds of feet of ice, it also provided us with an exact measure for past atmospheres.

Secondly, and perhaps much more ominously, it showed us how very far beyond any climate comparable to that great span of time we’d already come.

102 ppm higher than at any time in the last 800,000 years

Humans have now pushed the CO2 boundary 102 parts per million higher than the context provided by the last 800,000 years. It’s kind of a big deal when you consider that a mere fluctuation of about 100 parts per million CO2 was enough, when combined with changes in orbital forcing, to set off feedbacks resulting in a 4 C temperature change globally (8 C change for the Antarctic environment) as ice age proceeded to interglacial and back.

source : World CO2 Averages Touch 402.2 PPM Daily Values

Further read : Links between atmospheric carbon dioxide, the land carbon reservoir and climate over the past millennium


What are these Gizmos at Mauna Loa Observatory?

I am going to take a guess here because I have not used these instruments in real life but given the content of this Mauna Loa Observatory I Exploratorium video - fast forward the video to 3:43 and see the yankee name on that instrument.

Then I did a google search on that and got this link - Yankee list of products

So A is a Pyranometer and B is a  Ultraviolet Multifilter Rotating Shadowband Radiometer. I am not too sure on C and it probably is a actinometer. You can take a look of that here - Actinometer

The respective data sheets give information on both of those products.

1) Ultraviolet pyranometer

As this AMS glossary definition mentions a pyranometer measures both direct solar radiation(radiation that has not been scattered or absorbed) as well as diffuse sky radiation(radiation that is scattered)

Specifically this ultraviolet pyranometer measures both UV-B and UV-A rays.
This link covers the difference btween UV-B and UV-A rays. Specifically UV-A rays penetrate deeper into the skin than UV-B rays.

2)  Ultraviolet Multi-Filter Rotating Shadowband Radiometer

This one measures the diffuse and total global irradiance and computes direct irradiance at four or seven narrow bandwidth wavelengths(hence the term multi filter). One can see real time data for sites across the US  at this site - UV-B monitoring

3) Originally I thought C was a actinometer but when I look at this image Downwelling SURFRAD instruments I am going to say it is a LICOR PAR sensor(PAR is  Photosynthetically active radiation). The reason is because of the instrument inventory provided in this URL - SURFRAD BOULDER CO. If you notice in the NOAA ESRL image there is an instrument that  has a shape of a long column(in grey and to the right of the black colored instrument that is actually a MFRSR) that looks very similar to OP's C instrument.

You can now guess why that observatory has these set of instruments. It is at an altitude and that is a good place to study effect of Solar irradiance(less pollution)


How do I convert kg·kg⁻¹ to ppbV (parts per billion volume)?

So if you have a mass-mixing ratio, you effectively $\frac{ \text{kg pollutant}}{\text{kg dry air}}$. PPBV is parts per billion volume, or number of molecules of pollutant per billion molecules of dry air. Since not all particles weigh the same, you must use a conversion factor. Consider molar mass, which is the ratio of moles (a unit describing the number of molecules/photons/atoms) to mass. Ozone has a molar mass of 48 kg mol$^{-1}$. Dry air doesn't have a molar mass per se, but an effective molar mass may be computed by a weighted sum of the molar masses of the consitituent chemicals (or you can Google it). Afterwards, you may have to multiply by a billion.$$\therefore \frac{ \text{kg pollutant}}{\text{kg dry air}} \times\frac{\frac{\text{mols of pollutant}}{\text{kg of pollutant}}}{\frac{\text{mols of dry air}}{\text{kg of dry air}}}=\frac{\text{mols of pollutant}}{\text{mols of dry air}}$$


Can a microGPS tracker trace the path of an underwater drainage conduit?

GPS units require a clear view of the sky to fix their position. Because unlike radio signals used for communications, once the GPS signal have bounced in a wall becomes useless for computing the receiver's position. Therefore, the GPS would loss fix shortly after entering the pothole.

The studies made in the area that determined the point at which the water reenters the river, claim that the flow of water keep objects at the bottom of the pothole, explaining why they never resurface. So there is a high chance that you wouldn't see your GPS ever again.

However, if your GPS were to resurface, it would fix its position again soon after regaining a clear view of the sky. So, if you recover it (or if it had the capability to transmit its position in real time), you won't see a record of the track followed by the device, you would see only the entry and exit point.

For such problems, similar to a car going trough a tunnel, the GPS is usually augmented with inertial navigation systems that can estimate the displacements and compute the position by dead reckoning from the last GPS fix. Despite that the turbulence within the water flow in the pothole would make very challenging to keep track of the trajectory of the device underground, a sophisticated enough device should be able to do it.