Does the global temperature vary daily (hotter and colder days)?

The site http://www.karstenhaustein.com/climate.php comes closer to answering your main question with a daily anomaly graph:

Indeed it's still not the actual average temperature... and I was quite interested to see if there are annual global fluctuations in global mean temperature.  Surprising how much focus is on anomalies, but how little most sites note the mean temperature itself.  But eventually I found NOAA's monthly global climate reports, and was able to piece together the "globally averaged temperature over land and ocean surfaces" for each month and put together this graph:

(One trouble to point out in global totals such as these require the whole globe... so observation of the full far reaches... but we still have a somewhat limited surface observation networks in spots, and each satellite can only see a portion of the globe at one time, and all it's put together by varying data assimilation methods, so there will be some limitations\variation in any global estimates of it [as you can see later down that Karsten Haustein's page in the section comparing CFSR-GFS, NCEP reanalysis, and GISS temperatures])

But Karsten's graph above and all the other plots from their site are useful in showing real-time and the past that there are definitely some real oscillations day-to-day, but also that there is indeed quite a bit of stability whereby large regions of hot temperatures will tend to be balanced quite a bit by reduced temperatures elsewhere.

This conceptually would seem to make sense to me, as in the end the guiding framework would be that the energy put into the Earth system (by solar radiation) must equal the energy coming out in the long run.  That in itself wouldn't prevent fluctuations in the radiating temperature/energy sent out to space (related example: if you put your food in the oven, it takes in some of the energy, radiating less than it receives, and thereby gaining temperature until it gets up to temp).

This is one reason I should expect the global average temperature as a whole does shift some through the year: because water changes temperature more slowly than land, and the NH and SH have different coverage, there should probably be differences/lag in temperature and energy absorption/emission depending upon which portion of the Earth is receiving more sunlight.  Additionally, while the sun's energy is very constant, and the tilt only changes which region receives the energy but not the total amount incoming, there will actually be some overall change in how much energy we get into the lower parts of the atmosphere/to Earth's surface globally day-to-day and over longer periods due to variation in how much snow, cloud cover, and aerosols absorb/reflect some of the energy before reaching near the surface.

Overall, this would make sense to see a global peak in July (NH summer), when both more of the "warm Hemisphere" receiving increased energy is land, and more less of the "cool Hemisphere" is land able to hold snow cover.

When it comes to any specific layers within the Earth system, be it the surface ground/water, or the atmosphere at 2 meters above the ground, or any other height for that matter, I'd expect the answer would likely be the same: there is some fluctuation both daily and seasonally.  It's indeed not a zero-sum game because of the variations in the makeup of the globe.  But because the overriding principle is net energy balance of the Earth, those daily/seasonal changes are likely kept to a few degrees tenths of a degree in the short-term and a few degrees Celsius innerannually.
The ground/ocean are the primary heat source of air near the ground (air itself doesn't absorb much solar energy).  So generally fluctuations in global average air temperature (at 2 meters) should connect very well to changes in global average ground/water temperature... though differences in heat capacity and absorption spectra between air/soil/water/etc likely cause the sizes to be different, and probably small differences in the synchronization as well.  But overall, they should have very similar patterns.


Where are the oldest igneous rocks found?

Zircons from Australia at 4.4Ga, and perhaps basalts from a Canadian island at 4.5Ga.

It would interest you to know the quest of Boston University geochemist Matthew Jackson, who is searching for the oldest basalt and mantle rock that exists.

His work isn't entirely agreed upon, as they are using all kinds of difficult isotopes which are a subject of controversy. Probably the most current information on early basalts are the claims and counter claims relating to Matthew Jackson in published articles, which have a lot of chemistry in them.

http://news.nationalgeographic.com/news/2010/08/100812-worlds-oldest-rocks-magma-earth-nature-science/

https://www.bu.edu/today/2012/little-rock-at-center-of-big-controversy/

https://scholar.google.fr/scholar?hl=en&as_sdt=0%2C5&q=tungsten+basalt++oldest&btnG=

"We've been looking for pieces of the mantle that might have survived the chaotic mixing and churning within the deep Earth," said Boston University geochemist Matthew Jackson.

"We found rocks that reached the surface some 62 million years ago—suggest a whole reservoir of the primordial rock could still lie somewhere beneath the Arctic"

There are moon basalts from 3.7 Ga years ago, they are a bit mysterious, and lunar plagioclase feldspar at 4.5, appear to have formed when feldspar crystallized and floated to the top of a global magma ocean that surrounded the Moon soon after it formed.


The Dust Bowl: how's the recovery of all that topsoil going?

Soil is not a single uniform material. When wind erosion takes hold, as in the infamous 'dust bowl' of the 1930s, it is the uppermost A horizon, and to a lesser extent the B horizon that is mainly lost. The lost soil takes with it most of the organic carbon, and it is this component that is most difficult to replace.

Rates of soil loss are primarily factors of the underlying geology and climate. A wetter and warm climate will regenerate soil very much faster than a cold dry climate. Basalt and shale will break down into soil much faster than, for example, quartzite or granite. The rate of rock weathering is not quite the same as the rate of soil formation.

As a first approximation, rate of weathering = rate of soil formation + rate of mass loss by various processes.
Wakatsuki and Rasyudin (1992) Rates of Weathering and Soil Formation, Geoderma, V52, 3-4, gives a good assessment of such rates.
Their best estimate is that soil formation occurs at 370–1290 (mean = 700) kg ha−1 yr−1. Or roughly 0.3 mm per decade, excluding the lost organic carbon. This is equivalent to about 3 mm of new soil generation since the great dust bowl.

In other words, no, the lost soil is nowhere near replenished yet. Moreover, the impact of climate change does not bode well for the future of soil regeneration.


Do archaeologists deliberately leave parts of sites untouched so that someone can come back later?

Yes.

From this article in National Geographic:

  The last step before digging is to divide the site into a grid to keep
  track of the location of each find. Then archaeologists choose sample
  squares from the grid to dig. This allows the archaeological team to
  form a complete study of the area. They also leave some plots on the
  grid untouched. Archaeologists like to preserve portions of their dig
  sites for future scientists to study—scientists who may have better
  tools and techniques than are available today.

(emphasis mine)


How is the equilibrium of 21% oxygen in Earth's atmosphere established?

I'm not sure I can give a good technical answer. I don't think the amount of oxygen in the Earth's atmosphere is due to equilibrium but more of a consequence of the formation of the solar system, Earth chemistry and biology.

If you look at the formation, for inner planets, much of the gas and ices were blown off due to their inner orbits and the planets being too hit by very active Coronal mass ejections in the early solar system. There are 3 likely types of close to the sun planets:   1) small rocky planets (Earth, Mercury, Venus, Mars), 2) hot jupiters, which are large enough to trap hydrogen even though they're close to the sun and hot and 3) super-earths, which have enough gravity to trap hydrogen.

An abundance of hydrogen in a planetary atmosphere would likely make oxygen formation impossible.  The Oxygen would bind with the hydrogen.

The Earth didn't have the gravity to trap much hydrogen and some of the early atmosphere would have been blown off by large meteor strikes and by coronal mass ejections, which were much more common when the sun was young.

A clue to the Earth's atmosphere's formation is the formation of the oceans, because oceans would be impossible without an atmosphere.  The oceans formed 3.8 billion years ago, so we had to have an atmosphere, at least for about 3.8 billion years.

http://people.chem.duke.edu/~jds/cruise_chem/oceans/ocean1.html

The young Earth's atmosphere was mostly methane (CH4), ammonia (NH3), water vapor (H2O), and carbon dioxide (CO2) as per the link above, as soon as the Earth was cool enough, the water vapour turned into liquid water (rain) and the oceans began to form.

Fast forward to the Great Oxygenation event when cyanobacteria, pulled CO2 from the air and release O2.  Early on, the O2 binded with iron in the ocean and some of it likely reacts with CH4 and NH3 in the atmosphere when there is lightning. Over time, CO2 was pulled from the air, replaced by O2 and O2 reacted with CH4 and NH3, producing more CO2, H20, and N2 - the common elements we have today.

Oxygen levels in planets with cyanobacteria, likely depends on how much iron is dissolved in the oceans and how much hydrogen is in the atmosphere.  If there's not enough CO2 to produce enough O2 to saturate the iron and hydrogen, the planet probably never gets much O2 in it's atmosphere - so it's all about the ratio of early elements.    Super-earths might never get oxygen atmospheres - too much hydrogen.

You also get factors like the development of lignin (got that from Neil deGrass' Cosmos) - http://evolution.about.com/od/Cosmos/fl/Cosmos-A-Spacetime-Odyssey-Recap-Episode-109.htm

Lignin made trees possible, but nothing could eat trees, so trees captured more and more carbon, so CO2 levels fell and O2 levels rose.   About 100 million years later, termites evolved and the digestion of trees released much of this captured CO2 became possible and Oxygen and CO2 leveled out.

Shellfish, to make their shells, take more O2 out of the air than CO2 (calcium carbonate has lots of oxygen in it).   That's a slow process, but over time it takes some O2 out of the air, so over tens of millions of years, parts of the atmosphere are effectively sequestered and trapped in the Earths crust, but over time, some of this is also returned to the atmosphere with volcanic activity - so the type of life forms present is also a factor and the extent of tectonic activity is a factor as is, as is the presence of a Jupiter and how many comets are likely to hit the planet and the size of the planet.

It's more chance, the solar system and planetary factors that lead to a planet's atmosphere.

To answer your question:

  So if we increase the amount of oxygen, it will decrease over time and
  if we decrease it, it will be replenished.

Tough call regarding oxygen.   CO2 is easier.    Because there's a relatively small percentage of CO2 in the air, more CO2 will lead to some of it dissolving in the ocean as carbolic acid, though the warming of the ocean might also slow the oceanic absorption of CO2.     Because there's so much more Oxygen in the Earth, 21% vs 0.04% of CO2, a measurable increase, say 21% to 22%, you'd probably see a slight increase in dissolved O2 in the ocean, but beyond that, I don't think you'd see that extra oxygen go away any time soon.  My guess is, if such an increase was done, it would last a long time, hundreds of thousands of years if not millions, because oxygen sequestering is pretty slow.     Insects would get slightly bigger pretty quick.   That might be the most noticeable effect.

If you significantly increase O2 levels, say from 21% to 30%, things would become noticeably more flammable and over time, our lungs would probably get smaller and there would be other effects, probably.    But I don't believe there's any sort of equilibrium that would fairly quickly bring it back to 21%.


Skimming the paper, I believe the relevance of the wind stress curl is its relation to "Ekman pumping". I haven't found a simple, concise reference for this, but this page might be a good start, and this page has a couple of formulas about wind stress curl. I'll try to summarize here.

When wind blows over water, the top of the water starts moving. It shears against the water below it, so that water starts moving too. The momentum from the wind is transferred down into lower layers of the water. This water also feels the Coriolis force. The direction it ends up moving in depends on the balance of friction/drag and Coriolis force. On average, the water moves to the right of the wind in the northern hemisphere; if the wind is blowing northward, the water moves eastward.

Now imagine you have strong wind blowing northward at one location and weaker wind to the right of it. The water at the first location moves to the right, and it does so faster than the water at the second location (because the wind forcing the water is stronger at the first location). The water converges at the second location, pushing the water downward. This is how the curl of the wind stress (the northward wind changing in the east-west direction) is related to the water convergence (the eastward current changing in the east-west direction) and hence to water being pushed down or pulled up. Positive wind stress curl pulls water up; negative wind stress curl pushes it down.

The last relevant part here is that this kind of motion suppresses ocean mixing. The relevant sentence from that paper is

  The wind stress curl and hence Ekman pumping anomalies were negative, which also is consistent with relatively weak entrainment.

"Entrainment" is how much of the deep, cold ocean water mixes with the relatively warm upper ocean water, cooling it. The negative wind stress curl leads to water being pushed down and less deep water mixing with the upper ocean. The upper ocean stayed warmer, so the whole heat blob lasted longer.


I fly too, so I have first hand experience with movement of air below 13000 feet (Cessna 172). I have my simple version: in an otherwise calm weather a thermal has three stages which looked from profile looks like a tree. Base level near earth is the roots. Rising column is trunk. And cooling off and dissipating at high altitude is the canopy.

The part that has lifting power most is column because it picks up speed and momentum while it spins and whirls like the water draining into a sinkhole. The rising column can be pushed and swivel around by wind or topology of area surrounding it. The source of energy is dark surface or topology or local climate that can create layered temperature gradient from hot near ground to cold at altitude. Of course as we pilots of small planes know there are many other factors involved specially in mountains. Fire fighters are keenly aware of the tunneling effect and unpredictability of thermal near the canyons.


There are at least two effects are at play here:

Hawaii is a tiny speck of land in a big ocean; the odds of hitting any given spot in the Pacific with a storm in any given season is incredibly low.
The waters around Hawaii are deep and generally relatively cold, they suck energy out of storm systems that pass over them causing cyclones to downgrade into tropical depressions before they hit the islands, so there are plenty of storms but few are still cyclone grade when they arrive.


Is there a hemisphere where there's more land than ocean?

I wrote a little Matlab script to estimate this approximatively. Here is the result: colour denotes the total land area inside the hemisphere centred on a particular surface point. The red point is the maximum.

This gives me a maximum for the hemisphere centred on 1.7582°W longitude and 40.7692°N latitude, roughly in Guadalajara, Spain. If I calculated right this is 81% of all land, with 23.37% land area on the hemisphere (and 5.83% on the other hemisphere). So the answer to the question is no, there is no hemisphere with more land than ocean. There isn't even one with more than half land.

(Updated 2019-06-23 with higher resolution estimation, which moved the point south a bit.)


I just read an article saying that algae produces more oxygen than all the plants in the world!!
Edit: https://www.nps.gov/romo/learn/nature/algae.htm       First paragraph last lines


Are hurricanes/cyclones/typhoons in the Pacific Ocean usually larger than in Atlantic Ocean?

Typhoons in the western North Pacific ocean can be larger than hurricanes, because the great expanse of ocean water in the Pacific gives them more time and space to develop. Typhoon Tip in 1979 produced gale winds or higher over a diameter of 1400 miles. This is to my knowledge the largest western Pacific typhoon of record (it was also one of the most intense --- near-all-time-record maximum sustained winds of 190 mph, minimum barometric pressure an all-time record low of 25.6 inches of mercury). Typhoon Tip's 1400-mile diameter of gale-force or higher winds is almost double that of the largest hurricanes of record.


Why are CO2 sensors so expensive when CO sensors aren't?

Carbon monoxide (CO), natural gas & hydrocarbons, VOCs, ammonia, etc.

In this Chemistry SE answer and this Electronics SE question I discuss how the family of MOS gas sensors work. They can measure a large variety of different gasses that can react with atomic oxygen (O rather than $\small\mathsf{O_2}$).

  I'll quote from this question:

    ...sintered composite based on the semiconductor material $\small\mathsf{SnO_2}$, which is the metal oxide. The different sensors have different admixtures and operating conditions to achieve different sensitivities to different gasses.

    The principle of operation of MOS-type gas sensors is explained in Figaro sensors' Operating principle; MOS type.

  The Figaro link shows the operating principle in the GIF below:

   GIF (Source: Figaro)

  When the $\small\mathsf{SnO_2}$ is heated by the (usually 5V but not always) heater supply, oxygen in the air will dissociate at the surface and oxygen ions will stick to the surface, depleting the semiconductor and cutting off the flow of current. When a carbon-containing gas (e.g. $\small\mathsf{CO}$ or $\small\mathsf{C_xH_y}$ (but not $\small\mathsf{CO_2}$)) comes along, it will combine with the adsorbed oxygen and remove it from the surface. The more gas, the lower the equilibrium concentration of adsorbed oxygen and the higher resulting current flow through the semiconductor.

Carbon dioxide ($\small\mathsf{CO_2}$)

The $\small\mathsf{CO_2}$ sensor works on a totally different principle because $\small\mathsf{CO_2}$ is fully oxidized carbon, it will not react further with atomic oxygen.

Instead the $\small\mathsf{CO_2}$ sensors are either solid electrolyte chemical cells like the MG-811 or newer versions (see this question) or they are Non-dispersive Infrared Light sensors (NDIRs) based on optical absorption of a certain wavelength of infrared light, using a hot filament or other light source to produce IR and a narrow multilayer optical filter to select one of the strong absorption lines of $\small\mathsf{CO_2}$. The more $\small\mathsf{CO_2}$, the more the reduction in the transmission of light in the optical path of the sensor.


What is the time-lagged correlation between historical $\ce{CO2}$ records from ice cores and global temperature records?

From wikipedia:

  Studies of the Vostok ice core show that at the "beginning of the deglaciations, the CO$_2$ increase either was in phase or lagged by less than ~1000 years with respect to the Antarctic temperature, whereas it clearly lagged behind the temperature at the onset of the glaciations".$^{[1]}$ Recent warming is followed by carbon dioxide levels with only a 5 months delay.$^{[2]}$ The time lag has been used to argue that the current rise in CO$_2$ is a result of warming and not a cause. While it is generally agreed that variations before the industrial age are mostly timed by astronomical forcing,$^{[3]}$ a main part of current warming is found to be timed by anthropogenic releases of CO$_2$, having a much closer time relation not observed in the past (thus returning the argument to the importance of human CO$_2$ emissions). Analysis of carbon isotopes in atmospheric CO$_2$ shows that the recent observed CO$_2$ increase cannot have come from the oceans, volcanoes, or the biosphere, and thus is not a response to rising temperatures as would be required if the same processes creating past lags were active now.$^{[4]}$

Historical carbon dioxide record from the Vostok ice core - Carbon Dioxide Information Analysis Center, 2003.
Spencer R. Weart, 2006, The Discovery of Global Warming
Kuo et. al., 1990, Coherence established between atmospheric carbon dioxide and global temperature
More Notes on Global Warming - Physics Today, 2005


Is it true that "[sand] grains in the Coconino Sandstone come from the Appalachian Mountains"?

Jeffrey Ralh of Yale and coauthors published Combined single-grain (U-Th)/He and U/Pb dating of detrital zircons from the Navajo Sandstone, Utah, which concludes that Navajo sandstone originated from the Appalachian Mountains.  A review of the article is found here: http://www.geotimes.org/nov03/NN_navajo.html.

Rahl et al. propsed that a large river system transported the sediment.

However, Ralh's research concerned only Navajo sandstone, not Coconino sandstone as far as I know.

U–Pb ages of detrital zircons from Permian and Jurassic eolian sandstones of the Colorado Plateau, USA: paleogeographic implications does investigate Coconino Sandstone and other sandstones from the region and discusses what fraction are of Appalachian origin and transport mechanisms.

34% of Coconino Sandstone zircon grains are reported to be of Appalachian origin in table 4.


Where do rivers like the Rio de la Plata end and the ocean begin?

In the case of Río de la Plata, part of it is history and politics, and part of it is oceanography.

Most of Argentina and Uruguay considers Río de la Plata as a river (thus, the name, río) and as such it is the widest river in the world (maximum width >200km). Río de la Plata is formed as the confluence of the Paraná and Uruguay rivers and results in a pretty wide estuary with Montevideo (Uruguay) in the northern shore.

As can be seen in the following satellite image, the combined discharge from the Paraná and Uruguay rivers creates a current that flows into the Atlantic Ocean and that is visible under calm wind conditions and high discharge periods.

Source: https://eoimages.gsfc.nasa.gov/

Spanish and Portuguese explorers in the XVI century described Rio de la Plata as a "Mar Dulce" (freshwater sea). The Italian explorer Sebastiano Caboto explored the area and traded silver with the local Guaraní tribes and thus gave it the name of "River of Silver".

In practice, the system is best described as an estuary: neither river nor ocean, but an area of freshwater and saltwater mixing. In the area of Montevideo, the salinity in spring is around 10 g/kg (way lower than ocean salinities ~30-35g/kg), but it can be higher in periods of low discharge. In the area of Buenos Aires, salinities below 5 g/kg are commonly found and thus, it makes sense to call it a river. Most oceanographers agree that the system is a salt-wedge estuary, with freshwater flowing near the surface toward the ocean and saltwater intruding landward near the bottom of the estuary.

Salinity of the Rio de la Plata: Source: Guerrero, R.A., Lasta, C., Acha, E.M., Mianzan, H., Framiñan, M., 1997. Hydrographic Atlas of the Río de la Plata. CARP-INIDEP, Buenos Aires, Montevideo.


When specifying phase and amplitude for a tidal constituent, what date/time does phase start from?

Tidal constituents follow the expression: $\eta(t) = A cos (\omega t + \phi)$, where $\eta$ is the tidal elevation at a specific time, $A$ is the amplitude of the constituent, $\omega$ is the speed of the constituent (the rate of change in phase), and, finally $\phi$ is the phase of the constituent at the initial time from which the time is measured. The phase, $\phi$, is measured with regard to the equilibrium tide.
Thus, the short answer is that the phase is usually referring to the delay (in degree) from the theoretical equilibrium tide. From the NOAA glossary for phase lag (or phase epoch, not to be confused with the tidal datum epoch):

Angular retardation of the maximum of a constituent of the observed tide (or tidal current) behind the corresponding maximum of the same constituent of the theoretical equilibrium tide. It may also be defined as the phase difference between a tidal constituent and its equilibrium argument. As referred to the local equilibrium argument, its symbol is $\kappa$. When referred to the corresponding Greenwich equilibrium argument, it is called the Greenwich epoch and is represented by $G$. A Greenwich epoch that has been modified to adjust to a particular time meridian for convenience in the prediction of tides is represented by $g$ or by $\kappa'$. The relations between these epochs may be expressed by the following formula:
$G = \kappa + pL$
$g = \kappa' = G – aS / 15$
in which $L$ is the longitude of the place and $S$ is the longitude of the time meridian, these being taken as positive for west longitude and negative for east longitude; $p$ is the number of constituent periods in the constituent day and is equal to 0 for all long-period constituents, 1 for diurnal constituents, 2 for semidiurnal constituents,and so forth; and a is the hourly speed of the constituent, all angular measurements being expressed in degrees.


How can I create a CF compliant netCDF file?

So far this has been the most suitable answer to my question...

NOAA's National Oceanographic Data Center has posted NetCDF Templates v1.0 the CDL templates on their web site. These can be used with netCDF Operator (NCO) commands to create Climate and Forecast (CF) compliant files.

http://www.nodc.noaa.gov/data/formats/netcdf/
http://nco.sourceforge.net/
http://cf-convention.github.io/index.html


Can the overuse of geothermal energy become an environmental concern?

No, this seems highly unlikely.

According to online sources:

Average human power consumption in 2008 was estimated at 15 TW.

Total annual heat loss from the Earth due to the surface heat flux is estimated at 44.2 TW.

Estimates of the electricity generating potential of geothermal energy around the world are consistently less than 2 TW.

So although the average power consumption is a surprisingly large fraction of the total geothermal heat flux, the part that might possibly be extracted for power is quite small.

There are much more concerning environmental impacts to geothermal power development than freezing the core and destroying the Earth's Magnetic field. These include increased rates of release of carbon and sulfur into the atmosphere and land use issues.


Why silicon is abundant in earth surface?

Silicon, in the form of silica (oxidised silicon: Si4+ or SiO2), is indeed very common on Earth's surface.

This answer has two parts: why is silicon common in the Earth as a whole, and why it is concentrated particularly in the crust (therefore the surface).

Why is silicon common in the Earth

Silicon forms in nucleosynthesis processes in large stars (larger than our suns) and in supernovae. Turns out that quite a lot of silicon can be formed this way. When our solar system was still a hot molecular gas cloud, our region in place was rich in silicon (among other elements) so eventually Earth has lots of silicon in it. This is slightly beyond my field of expertise, so I will refer to the link daniel.neumann gave in his comment and to this good explanation at UCSB Science Line.

Why is silicon extremely rich in the Earth's crust?

Now we know there's quite a lot of silicon in the Earth to begin with. How do you end up with even more silicon in the crust (outermost layer) than in the mantle (middle layer, between the crust and the iron metallic core)?

The answer lies in what happens to rocks when they melt. You have a rocky mantle, with let's say 35% to 45% of SiO2. When this rock gets heated or decompressed (or wet, but nevermind this for now), it melts. But it doesn't melt completely, it melts only partially. This will always be richer in SiO2 than the original rock, and the residue of the melting now has even less SiO2. Once SiO2-rich melt moves upwards in the Earth (sometimes even erupting as volcanoes), it moves more SiO2-rich material to the crust. Over billions of year and large successive partial melting events, you end up having quite a lot of SiO2 in the crust.

This gets even better, because in those SiO2-rich rocks, you also have lots of quartz - which is a mineral composed of pure SiO2: 100% SiO2. This is a very resistant mineral to alteration and weathering. So if you have a granite that has only a third of quartz, with time the other two thirds (mostly feldspars) will decay and turn into clays (aka dust, mud). Only the quartz will be left behind, and the rest will wash away with water to the oceans (eventually). This is why you have impressive sand dunes which are "seas" of almost pure SiO2:

Some other questions on this website you might be interested in:

What was the likely composition of Earth's early crust (how did crustal composition evolve)?

Why do felsic materials have lower melting points than mafic?


If the nitrogen and oxygen in our atmosphere were doubled would the pressure double?

The surface pressure is just the weight of the atmosphere per unit area, so yes.

The density decreases with altitude so there is no well defined "top" to it. Assuming constant temperature (Isothermal-barotropic approximation) the density decreases exponentially with altitude.

If it were doubled there would the same portion of mass above any given altitude (but more mass above any given altitude).


As the name suggests it is a region of uncertainty.
There are many uncertainties when modeling and predicting weather systems.
When meteorologists model the path of a cyclone/typhoon/hurricane they never know for certain where a cyclone will actually end up. At any point along its path a local variation may cause it speed up, slow down, rotate at a slightly different rate or slightly change its path, left or right.
Meteorologists run several models for such cyclone systems on computers. Each uses either a different algorithm and/or different weather parameters. The results of all the models are then used to determine a region where the cyclone is likely to be in with a given time frame.
The greatest certainty is closest to the cyclone. The further away the projected path is from a cyclone the greater is the uncertainty. This results in a larger spread of possible locations where the cyclone could eventually be. When drawn on a map this region looks like a cone.


Is there a database of global rainfall time series?

Yes. Nearly global satellite and radar derived rainfall data are hosted by NASA Goddard Space Flight Center, namely:

Tropical Rainfall Measurement Mission (TRMM) aboard the TRMM Microwave Imager (TMI), a multi-channel, dual polarized, conical scanning passive microwave radiometer designed to measure rain rates over a wide swath under the TRMM satellite. TRMM was launched on November 27, 1997 into a semi-equatorial (+/- 35 deg) orbit carrying 5 instruments. Three levels of data processing are available on the NASA's server, where higher level indicates more processing, quality control, and merging of multiple raw datasets. For your purposes, use level 3 TRMM as it combines satellite data from multiple swaths with precipitation radar data and other sources, and provide 3-hourly data in the 60S-60N latitude band, at 0.25 degree horizontal resolution.
Global Precipitation Measurement mission was launched in early 2014, and provides full global coverage at 0.1 degree horizontal resolution at 30 minute intervals in time. This product is in its very early stages, and is still under development and testing.

In both cases, if you are interested in more precise rainfall estimates at a particular point in space and time, look at level 1 data. It is raw data that provides a time step for every single point along an orbital trajectory of the satellite. Use with caution.

In addition, ground validation data is available on the same server, and some or most of these data is assimilated (merged) into level 3 TRMM and GPM products.

Once you download the data, you can use their data viewer, THOR, or use your favorite programming language or analysis software to display it yourself.


Will the ocean eventually erode all land?

Continents are made up of different, lighter materials than oceans and both continents and oceans "float" on the mantle. Continents are also thicker than oceans so erosion does not only need to take care of the ~5 km which is above sea level but it should also erode away the continental root (which can be several 10's of kilometers until the continental crust is actually slightly thinner than oceanic crusts are today.

However tectonics is not the only source of topography which can easily be seen if we look at Mars where a hotspot has created an enormous mountain on a tectonically inactive planet.

So if you want to end up with a topography free planet you need to shut down all possible mantle plumes too.


Wobbly Tire Theory -- Is there an existing theory that fits the following description?

I don't know if this theory has any formal name, but of course you are correct in assuming that any mass redistribution on or in the planet will affect it's axis of rotation, causing a wobble. Small re-distributions are happening all the time with growing and melting ice, ocean currents sloshing water from one side of an ocean to another (as in the El Nino). Theoretically, a whale swimming across an ocean will create an axial wobble, albeit far too small to measure. Earth and sea tides, climate change, plate tectonics etc... The list goes on and on, with multiple processes each causing a slight tilt in the Earth's axis. This ranges from barely detectable sub-milimetre range to thousands of kilometers (over geological time - hundreds of millions of years).

In addition to the above random fluctuations there is also the 'Chandler wobble' which is a predictable cyclic wobble in the Earth's axis, of about 9 metres, over a period of 433 days.

As for human impacts, until recently I would have said that they were puny compared to natural processes. However, recent research points to significant and growing change in the Earth's rate of spin due to human induced climate change. This could have interesting 'knock-on' effects upon the spin axis. The effect is absolutely miniscule, but as the Earth's spin slows, there is likely to be further de-coupling of spin rate between the Earths crust/mantle and core which could well be an additional component to the axial wobble.


What was the Amazon like during Green Sahara?

According to the article Africa: Greening of the Sahara (Claussen et al.), the 'Green Sahara, occurred during the Holocene climatic optimum, occurring at the same time as the  "African Humid Period", also similar ages to the events mentioned in your 3rd link.  All occurring during the mid Holocene

At the same time in the Amazon region, according to the article Responses of Amazonian ecosystems to climatic
and atmospheric carbon dioxide changes since the
last glacial maximum (Mayle et al. 2004), was

  reduced precipitation in the Early–Mid-Holocene (ca. 8000–3600 years ago) caused widespread,
  frequent fires in seasonal southern Amazonia, causing increased abundance of drought-tolerant dry forest
  taxa and savannahs in ecotonal areas.

Although, this effect was not uniform over the entire Amazonian Basin, the authors conclude from pollen, charcoal and other samples, that the Amazon Basin had far less precipitation (up to 40 less in places), which caused

  increased fires and consequently greater ecosystem
  disturbance, which would be expected to have caused
  structural as well as compositional changes to plant communities,
  such as expansion of drought-tolerant lianas and
  semi-deciduous taxa within forests and expansion of savannahs
  at forest–savannah ecotones. Populations of coldadapted
  species (e.g. Podocarpus) were largely eliminated
  from the Amazon lowlands during this interval, and cloud
  forests on the eastern flanks of the Bolivian Andes diminished
  while open, grass-dominated ecosystems expanded.


How to derive the (dry) deposition velocity for particles in the atmosphere

After some more work I got it working, this might not be the shortest solution possible. There are no further assumptions needed, just pure algebra.
The solution is a bit tedious to reach, so it's not too surprising that this is usually not included in the literature.

Start by splitting $(3)$ into two separate equations
$$
\begin{cases}
\frac{C_3}{r_t}=\frac{C_3-C_2}{r_a}+v_g C_3\hspace{10mm}(4)\\
\frac{C_3}{r_t}=\frac{C_2}{r_b}+v_g C_2\hspace{17mm}(5)
\end{cases}
$$
Get $C_3$ by multiplying $(5)$ with $r_t$ and breaking out $C_2$:
$$
C_3 = C_2 r_t (\frac{1}{r_b} + v_g)\hspace{10mm}(6)
$$
Divide $(4)$ by $C_3$:
$$
\frac{1}{r_t}=\frac{1-C_2/C_3}{r_a}+v_g\hspace{10mm}(7)
$$
Insert $(6)$ in $(7)$:
$$
\frac{1}{r_t}
=\frac{1-\frac{C_2}{C_2r_t(1/r_t+v_g)}}{r_a}+v_g
=\frac{ \frac{1}{r_b}+v_g-\frac{1}{r_t} }{ r_a(\frac{1}{r_b}+v_g)}+v_g
\hspace{10mm}
$$
Move $r_t$ to LHS, i.e. add $\left(r_t \cdot r_a(\frac{1}{r_b}+v_g)\right)^{-1}$ to both sides:
$$
\frac{1}{r_t}\left(1 + \frac{1}{r_a(\frac{1}{r_b}+v_g)}\right)
= \frac{1}{r_a}+v_g
$$
Divide by $\left(1+\frac{1}{r_a(\frac{1}{r_b}+v_g)} \right)$ on both sides:
$$
\frac{1}{r_t}
=\frac{1/r_a+v_g}{\left(1+\frac{1}{r_a(\frac{1}{r_b}+v_g)} \right)}
$$
Multiply numerator and denominator (RHS) by $r_a$ and simplify:
$$
= \frac{1+v_g r_a}{\left(r_a+\frac{1}{(\frac{1}{r_b}+v_g)} \right)}
= \frac{1+v_g r_a}{\left(r_a\frac{(\frac{1}{r_b}+v_g)}{(\frac{1}{r_b}+v_g)}+\frac{1}{(\frac{1}{r_b}+v_g)} \right)}
= \frac{(1+v_gr_a)(\frac{1}{r_b}+v_g)}{r_a(\frac{1}{r_b}+v_g)+1}
$$
Re-organize the numerator and split it:
$$
=\frac{ \frac{1}{r_b}+v_g+v_g\frac{r_a}{r_b} +v_g^2 r_a }{r_a(\frac{1}{r_b}+v_g)+1}
=\frac{ \frac{1}{r_b}+v_g\left(r_a(\frac{1}{r_b} +v_g)+1\right) }{r_a(\frac{1}{r_b}+v_g)+1}
=\frac{ \frac{1}{r_b}}{r_a(\frac{1}{r_b}+v_g)+1} + v_g
$$
If we now move $r_b$ in the first term on the RHS to the denominator we end up with the final expression:
$$
\frac{1}{r_t} = \frac{1}{r_a + r_b + r_a r_b v_g } + v_g
$$


Differences between TEOS-10 and EOS-80 for salinity

From my reading of the primer and manual, I would summarize the difference as follows. Practical salinity is calculated directly from the conductivity of seawater (which is what's most often measured by buoys, floats, and other autonomous systems) whereas absolute salinity is based on the density of the seawater. Practical salinity is essentially measuring the distribution of ions in the seawater. Absolute salinity is based on the mass of all non-H2O material, whether it's ions, gases, or solids. Relating salinity to mass, rather than conductivity, makes writing conservation equations much more straightforward; a dissolution of HCO$_3^-$ into H$^+$ and CO$_3^{2-}$ changes the practical salinity but not the absolute salinity. Basing salinity on mass also makes the thermodynamics much simpler, but I'll address that in your other question.

Differences between the practical and absolute salinities crop up where there are big differences in the composition of seawater, especially in its dissolved but non-ionic components. Page 14 of the manual (Fig 2) has some maps of what this looks like: Large deviations in the lower-salinity Pacific, and large deviations at depth where density and conductivity aren't so closely related. Absolute salinity can handle measurements of seawater composition in a way that practical salinity doesn't.


Can Volcanic Eruptions Help Combat Global Warming in the Long Run?

The subject you are looking for is called climate engineering. In general, changing atmospheric composition in order to achieve a cooling effect that counteracts climate change is conceivable.

Whether triggering volcanic eruptions is the most feasible approach (or possible at all) is of course a completely different issue. From my understanding of volcanoes, you would really need massive eruptions with large plume-heights to achieve long-term impact.

Also note that we would need to sustain the resulting atmospheric change over a long time. And the side effects of releasing large amounts of pollutants into the atmosphere need to be considered too.

For some more aspects read this answer to a related question.


Here is what I found if useful for others -

Oceanic Wave Clarification

Wave position in space (x,y) and in time (t) are different concepts

Ocean waves in time are a vertical oscillation generated most often from surface winds creating a circulation (eddy). There are no 'leading waves' to a 'big wave' rather simply a continual progression in size.

Ocean waves in space are generated from the simple motion of the wind. As the depth decreases the energy density of the wave increases, increasing the wave amplitude

Illustration (1)

Common Vocabulary (if useful)

Reference

(1) Quora - >When do waves stop forming in the ocean?
(2) Hyperphysics - Ocean Waves


Which theory is stronger, that iron came from outside or was formed within earth?

The only elements that were formed on Earth are those produced by radioactive decay. There are four natural decay chains that start with transuranic elements and none terminate in iron; neither do the decay chains that are artificial or those that result from cosmic radiation. So all of our iron is from the Earth's formation or meteor impacts since then.


Doesn't Increase of Potential Temperature with Height contradict Adiabatic Nature of Processes within Troposphere?

If we'd be living in a dry atmosphere your reasoning is indeed correct. Air would rise adiabatically and air would loose about 9.8 °C/km (dry adiabatic lapse rate). This means constant potential temperature. However, Earths atmosphere isn't dry. As soon as a rising, moist air parcel reaches saturation, it will rise with a moist adiabatic lapse rate (6-7 °C/km). Potential temperature will rise (because if the parcel falls down again it will be warmer at the same level - see below). This causes clouds and sometimes rain and thus, reduces the overall water content in an air parcel.
If such a parcel is now going to fall again it will gain temperature according to the dry adiabatic lapse rate (because it lost water during ascension). Lets say initially a parcel starts rising with moist adiabatic lapse rate with temperature $T(t=0)$ and then falls down again and reaches the same level at $t=1$. You will then observe that $T(t=0)< T(t=1)$. Thus, potential temperature must have increased as the parcel was rising.


What geological processes would 'restart' subduction processes?

Subduction is ultimately driven by the heat flow process of mantle convection. A mantle plume beneath a stable plate will ultimately cause that plate to split, a la the African rift zone we observe today.

The crust of the earth is very thin compared to the mass of flowing material beneath it. As my global geophysics prof taught us, the fact that the earth has a solid outer "skin" is a consequence of the thermal conditions around the earth's surface and geochemistry, but that has little to no effect on the thermal conditions within the planet that ultimately control thermal convection that expresses itself on the surface as plate motions. I.E., the thermal mass of the crust is inconsequential when considering the thermal mechanisms that drive the mantle and outer core. Heat makes the plate go!

On the surface, plates may move, be created or destroyed, but thermodynamics tells us these are consequences, not drivers. We may observe evidence of past situations where plates appear to be static with respect to the underlying mantle motions, but this does not reveal any new mechanism that would suggest plate tectonic theory would not predict such circumstances.


The origin of spurious high frequency waves in numerical weather prediction

I don't have a mathematical illustration at the moment (though I might edit this answer if I come across something in my notes). But the basic problem is sound waves. If you make a numerical model of the full Navier-Stokes equations, that model has to allow sound waves to propagate. That implies that the time step used has to be incredibly short -- under 5 minutes for sure for a grid size of 100 km, and preferably much shorter than that. So sound waves are fast-moving, high frequency, and don't really contribute to weather. That's why weather prediction models tend to use the primitive equations: these equations are very similar to the Navier-Stokes, but sound waves aren't solutions to these equations.

Hopefully that's a start. Feel free to ask for a clarification on how this filtering is done in practice. Like I said, I'll look through my notes for something, I remember doing a problem set involving this.

Edit: Here are some notes from David Randall on the anelastic and Boussinesq approximations. These notes are in more of a classroom format, but at the end they derive the link between the continuity equation and sound waves.

Briefly, sound waves arise from variations in density that are independent of variations in enthalpy/temperature. The continuity equation in general is $ \frac{\partial \rho}{\partial t} + \nabla\cdot (\rho \vec{u}) = 0 $ in which density variations can be accompanied by contraction and expansion of the fluid. The anelastic equations filter out sound waves by replacing this dynamic equation with a diagnostic one, removing the time derivative: $ \nabla\cdot(\rho_0 \vec{u}) = 0 $ where $\rho_0$ is a background density profile. No more time derivative for density means no more expansion and contraction except under changes in enthalpy.

This is how sound waves are filtered out. I realize that I didn't read the question closely enough, though. If you're working with an LES, at that fine of a spatial resolution, you're probably 1) already using the anelastic equations, and 2) properly resolving a lot of the high-frequency oscillations anyway. As @milancurcic mentioned, gravity waves become an issue as the next-highest frequency waves. These notes go through the problem of gravity waves in a shallow-water model, and this article (behind a paywall) shows how a good choice of initialization can help eliminate those waves.


Is this paper attributing a change in polar wander to climate change?

The term ‘polar wander’ is ambiguous. In this case it's got nothing to do with the magnetic poles, but rather with the Earth's spin axis. If you think about a desk globe mounted on an axle, the poles under consideration here are the points where the axle intersects the globe's surface.

The paper is essentially saying that climate changes are changing the distribution of ice and water on the surface of the planet, and this in turn is shifting the spin axis slightly. You're right that the mass of material on the Earth's surface is dwarfed by the mass under the surface; however, if you look at the paper you'll see that they're talking about miniscule shifts in the axis. The changes shown in Figure 1 are on the order of tens of mas (milliseconds of arc) over a few decades. One mas is one 3.6-millionth of a degree, or about 3.09 cm as measured on the Earth's surface. So, at least at first glance, the changes don't seem too implausible.

You mention isostatic response as another concern, but this is a slow process which doesn't really come into play on the decadal time scales considered in the paper. Fennoscandia and northern North America are still rebounding isostatically from the last ice age.


How far up do you have to go before most of the atmosphere is below you?

Roughly 5.5 km, although the exact value depends on the weather.  All you need to do is to solve the hydrostatic equation and find the height at which the pressure is 50% of the height at sea level (or perhaps average elevation of Earth surface instead of sea level).  Any answer actually performing the calculation deserves upvotes more than I do ;-)

See, for example, Thickness of Earth's Atmosphere:

  Using boundary layer theory as an example, we can define the thickness of the atmosphere to be the altitude that encloses 99 percent of the total mass of the atmosphere. Looking at the chart, we can see that this seems to be about 31 kilometers. The halfway point, where half the mass of the atmosphere is below and half above occurs at 5.5 kilometers. Another interesting fact is that when you are cruising in a modern jet transport at 11 kilometers, you are above 77.5 percent of the atmosphere. The total mass of the atmosphere turns out to be 5.3 zettagrams (5.3 Zg).

I'm not entirely sure how the calculations in the linked article are performed, but I recall calculating this as a student and ending up somewhere around 5 km, so it sounds right.  Simple calculations often assume an isothermal atmosphere, which is of course not accurate, but good enough if you don't need to know the answer more precisely than within several hundred metre.

This page at Stanford reaches the same number.


What was the ocean circulation like during the time of Pangaea?

Here is an estimate from Beauchamp and Baud (2002), for parts of the ocean around Pangea, for the latter parts of it's existence (~300-250mya). It is based on various previous papers that looked at deposits of carbonates and phosphate deposits, and made a few assumptions, including a sufficient supply of silica and nutrient inputs, and environments suitable for particular biota, including particularly siliceous sponges:

Beauchamp, B. & Baud, A., 2002. Growth and demise of Permian biogenic chert along northwest Pangea: evidence for end-Permian collapse of thermohaline circulation. Palaeogeography, Palaeoclimatology, Palaeoecology, 184(1–2), pp.37–63. https://www.sciencedirect.com/science/article/pii/S0031018202002456


Would adding sulfur dioxide to the atmosphere have a global cooling effect?

There have been a range of studies on the issue published in Atmospheric Chemistry and Physics and other scientific journals.

The short answer is "yes." The longer answer is "yes, but...."

In Climatic impacts of stratospheric geoengineering with sulfate, black carbon and titania injection, Jones, et. al. (2016) note:

  In this paper, we examine the potential climatic effects of
  geoengineering by sulfate, black carbon and titania injection against
  a baseline RCP8.5 scenario. We use the HadGEM2-CCS model to simulate
  scenarios in which the top-of-the-atmosphere radiative imbalance due
  to rising greenhouse gas concentrations is offset by sufficient
  aerosol injection throughout the 2020–2100 period. We find that the
  global-mean temperature is effectively maintained at historical levels
  for the entirety of the period for all three aerosol-injection
  scenarios, though there is a wide range of side-effects which are
  discussed in detail.

Those side-effects would vary with the size of the particles used and the method and location of atmospheric injection, but would include:

Impacts on human health from increased particulates.
Changes in surface albedo from particulate deposition.
Changes in the amount and location of precipitation across the globe.
Increased stratospheric warming.
Changes in stratospheric ozone levels.

There would be no amelioration for other climate impacts such as ocean acidification.

  It is therefore important to note that the safest possible solution to
  avoiding the sort of climate change instantiated by, e.g., Fig. 6a of
  this report is to effectively mitigate greenhouse-gas emissions.

Other issues not addressed by this physics-based paper include:

The requirement for any geoengineering scheme to be maintained for decades or centuries.
The need for a substantial industrial base to manufacture and distribute the particulates involved.
The (presumed) need for an international body to manage the process and address political concerns such as the costs and benefits of the   geoengineering; such as if the process was going to increase or reduce rainfall to a particular region.


Why can't wave models model storm surge?

Yes. Spectral wave models cannot model storm surge because the wave energy balance equation that they integrate does not describe the physical processes associated with storm surge.

Wave models solve the wave energy balance equation:

$$
\dfrac{\partial E}{\partial t}
+ \dfrac{\partial (c_gE)}{\partial x}
+ \dfrac{\partial (\dot{k}E)}{\partial k}
+ \dfrac{\partial (\dot{\theta} E)}{\partial \theta}
= \rho_w g\sum S_i(x,k,\theta)
$$
where the terms on the LHS represent local change in time and advection of energy in geographical ($x$), wavenumber ($k$), and directional ($\theta$) space, respectively. The source terms $S_i$ on the RHS determine the growth and decay of wave energy due to wind input, wave dissipation, and non-linear wave-wave interactions.

While mean water depth, wind forcing, and background Eulerian currents all affect the evolution of wave energy, the wave energy balance equation only solves for the statistical distribution of wave energy and its change in time. It does not provide information about the change of mean water level or Eulerian currents. The simplest equation set necessary to explicitly model surge are the single-layer (2-D) shallow water equations:

$$
\dfrac{d\mathbf{u}}{dt}=-g\nabla\eta + \dfrac{1}{\rho_w} \dfrac{\partial \boldsymbol{\tau}}{\partial z}
$$

$$
\dfrac{\partial \eta}{\partial t} = -\nabla \cdot (\mathbf{u}(H+\eta))
$$
where $\mathbf{u}$ is the Eulerian velocity and $\eta$ is the displacement from the mean water level $H$. $\nabla$ is the horizontal gradient operator. $\dfrac{\partial \boldsymbol{\tau}}{\partial z}$ is the vertical stress gradient that forces the flow - essentially the difference between surface and bottom stresses. The momentum equation describes how the flow velocity changes due to horizontal pressure gradient and surface forcing (stress). The mass continuity equation describes how the water elevation changes due to divergence of the flow. For spatial scales larger than 10 km or so, Earth's rotation becomes important and the RHS of the momentum equation must include the Coriolis acceleration.

Another requirement for the model to simulate storm surge is to allow for wetting and drying. What this means is that the land cells, which are originally above mean water level, and thus not part of the model solution, can become wet once the water level reaches their height and "submerges" them. These grid cells then become part of the model solution. While this may sound obvious and physically intuitive, implementing a wetting-and-drying scheme in a model is a non-trivial challenge regarding software design.

When the wave and surge models are coupled, the Eulerian velocity field $\mathbf{u}$ is mainly forced by wave dissipation, and less by wind directly. The surface elevation changes in response, and together with Eulerian velocity feeds back to the wave model.


Correct way to spin-up for sensitivity analysis in a Global Chemical Transport Models

welcome to ES.
I'm not experienced in Chemical Transport Model, so my reply will be more on "general terms" and I'd be more than happy to see more specific answers.
That being told, in my experience with land surface and hydrological models, the spin-up period is heavily model- and application- specific. In some applications, for hydrological analysis of complex large basins, the spin up period of the model could require also some years of simulation. This is needed to stabilize all the "reservoirs" that the model uses to simulate the complex interactions between surface and subsurface hydrology. Using a "too short" spin-up period would seriously affect your results, but what is "too short" depends on your model.
The sort answer to your question would therefore be: "the longer the better", but this would also depend on the complexity of your model and the computing time that you need to dedicate to the spin-up period (i.e., if your model takes a week to simulate a month, then I would not suggest you to take a spin-up period of a year...).
So if this is not the case, and your model is pretty fast, I'd replicate the data that you prepared for the year 2009 as input for a "fake" 2008 and run the simulation from 2008 to 2010. Looking at the outputs of your model, then, you will see if there are weird trends that you could attribute to the spin-up going beyond the "fake" 2008. If this is not enough, you could use the same data also for 2007, and so on.
Additional info also here.
EDIT: I'm just realizing that yesterday I replied only to part of your question. My apologies.
I'll try to respond here to the question you made in your comment:

So that means even if I take the initial condition form year 2009, I
still need to spin up the model, if I do some other analysis (such as
sensitivity)? can't I directly use the initial condition from 2009
from baseline simulation in sensitivity simulation instead of spinning
up again, especially if the spin up time is very long and I would want
to save computation time?

This really depends on the inertia of the system that you are analyzing. It is very unlikely (at least, to me, and remember that I'm not familiar with these models) that you could get a system that is going to stabilize to different conditions (like removing the anthropogenic emissions) simulating just one year.
Look for instance at this example that comes from the User Guide of an open access hydrological model (LISFLOOD documentation, taken from here):

To better understand the impact of the initial model state on the
results of a simulation, let’s start with a simple example. The Figure
below shows 3 LISFLOOD simulations of soil moisture for the upper soil
layer. In the first simulation, it was assumed that the soil is
initially completely saturated. In the second one, the soil was
assumed to be completely dry (i.e. at residual moisture content).
Finally, a third simulation was done where the initial soil moisture
content was assumed to be in between these two extremes.

So, this part of the system (top layer soil moisture), is apparently stabilizing in about 150-200 days. After this period, the initial conditions (with and without spin-up) are basically irrelevant.
If you go to analyze other variables instead:

This part of the system, instead, takes about 2000 days to stabilize. This means that a proper initialization of this particular model in this particular application is crucial to get reliable results in "short" (<2000 days in this case) simulations.
Now, imagine that your system has a certain inertia to stabilize after a shock in the emission level (from the example you made in your question): if your situation is similar to the one in the first figure, one year spin-up would be enough and the comparison of the second year with and without anthropogenic emissions would give you something more or less informative. If your system has a slow response as the one in the second figure, then your results would be completely wrong even with the spin-up that you proposed.


Why are earthquake considered spot things?

Faults and discontinuities within the Earth's crust are rarely smooth and any smooth parts are short in length.

The degree of roughness along a fault or any discontinuity varies in strength and magnitude. This causes stresses to build up unevenly along faults and discontinuities. When the stresses are too large for one rough patch to withstand there's a break and stress is released causing an earthquake. This is why earthquakes occur at a particular location.


Would it be possible, from the earth’s creation or during its various geomorphological changes, for all the following hypotheses to be probable?

The second part of the question is easy to answer - given that the Arctic has been ice free in relatively recent geological history, e.g. in the Mesozoic, and it is expected to be ice free in summer within a few decades as a result of global warming, positing a habitable planet where polar oceans are navigable, at least in summer seems fairly safe.


How long did it take for Earth's magnetic field to first appear?

The age of the Earth's magnetic field could be as old as the existence of the physical conditions capable of generating a magnetic field. Because we believe the geomagnetic field originates from the liquid outer core, your question could be restated as: When did the Earth form a liquid core?

How the Earth's core formed is still not well understood and the area of research is referred to as planetary differentiation.


You are correct. Isotropy means that the property at some specified point (X,Y,Z) is the same, whether the measurement is made along any direction.

If the property varies depending on which direction you make the measurement in, then that property is said to be "anisotropic". For example, the permeability of a material (i.e. its ability to conduct fluids) may be anisotropic if fluid can move preferentially in one direction and it would be difficult for it to move in a different direction (like the tubes below). This means, the permeability of this material at a given point (X,Y,Z) depends on which direction you make the measurement, i.e. high permeability parallel to the tubes, low permeability otherwise.

Transverse isotropy (also called hexagonal symmetry) is a special kind of anisotropy in which there exists a special "axis of symmetry" such that the property you are measuring appears to be the same as you make measurements perpendicular to this axis. Basically, rotating around this axis of symmetry, the property looks pretty much the same, i.e. it is isotropic in this transverse direction. However, once you go off axis, then the measured property will change.

In geology (especially in sedimentary geology), transverse isotropy is usually a good approximation to many phenomena (elasticity, permeability, heat conductivity, etc.) due to the fact rocks are deposited mostly horizontally. This means that things will look very similar laterally (in both N-S and E-W directions) but very different vertically.

Finally, transverse isotropy is just an approximation to the much more complex nature of real rocks. If you were to add multiple sets of fractures to a rock on top of its layered nature, you will need to use a "less symmetric" model to describe it: orthorhombic, monoclinic, or triclinic. But for most practical purposes, transverse isotropy does a pretty good job.

Hope this helps!


Soil Science and the carbon cycle - is carbon released from soil into the atmosphere?

There are two ways carbon is released from soil.

The first is cellular respiration of plants that uses previously stored energy (visualized in this chart).

The second is when heterotrophs consume organic carbon below ground and respire carbon dioxide.

The sum of these is called soil respiration, which I think was the process you were asking about.


When was it ever considered that the desert might be "man-made", or otherwise anthropocenically-induced?

El-Baz has utilized satellite images to better understand the origin
  and evolution of desert landforms. He is credited with providing
  evidence that the desert is not man-made, but the result of major
  climatic variations.

  Does the passage refer to all deserts?

Geolmorphologists classify deserts as zones that take place in climatic arid regions where rainfall is relatively low, there are extreme daily temperature variations and the vegetable cover is reduced or non-existent. The climatic conditions result in desert typical forms as hamadas, caliches, or dunes. (Gutiérrez Elorza, M., 2008).

It is important to note not every arid region is a desert, but every desert, with particular forms, is an arid (or hyperarid) zone.

Source: research.net

The question is: can Climate Change and deforestation create deserts?

Answer is Climate Change and deforestation can create new arid zones. It can create the conditions to expand existant deserts, but the typical desert forms take some time to form, so deserts as El-Baz have not (yet) grow because of our actions on the planet.

However, other deserts as Sahara have expanded his area in the last century (Thomas, N. et al., 2017). The article of this asseveration quotes (anthropological) Climate Change as the main factor of this expansion.

So answering your question the passage you quote does not refer to all deserts if you consider man-made something that result from our emissions of greenhouse gases to the atmosphere.

Gutiérrez Elorza, Mateo (2008): "Geomorfología", Ed. Prentice Hall.

Thomas, Natalie and Nigam, Sumant (2017): "Twentieth-Century Climate Change over Africa: Seasonal Hydroclimate Trends and Sahara Desert Expansion". Journal of Climate, vol 31.


You need to define what you mean by 'adding more sun'. I'm asuming you mean 'increase the solar constant'.

The amount of water vapour in the air is, as a first order approximation, related to temperature - every degree of temperature rise gives us 7% more water vapour.  So if 'adding more sun' increases the temperature then it automatically increases water vapour.

Now, to add more sun without increasing the temperature, you'd have to compensate by doing something like painting large areas of land white; this would increase the Earth's albedo, reflecting the extra solar radiation. No temperature change overall, so no water vapor change.

The only direct effect of the sun on water vapor is something entirely different - through photo-dissociation. This is where the sun's UV rays directly break up water molecules.  However, in order to have an appreciable effect on the day to day concentration of water vapour, you'd need to replace the Sun with a much bigger and hotter star that blasted out far more UV radiation. The problem here is that everyone would die.

So as far as the question can be answered, it would be no under any realistic scenario.


Are there books or on-line resources about graphic design for geology?

There is an very detailed "Digital Cartographic Standard for
Geologic Map Symbolization" by the Federal Geographic Data Committee (FGDC) including e.g. color and pattern charts.

Check the main website for the latest version of the Standard, availabe in PostScript format, as pdf, or as ArcGIS10 template.


How much garbage goes into the Pacific Ocean every year?

I've been looking for information on non-plastic garbage, and haven't had much luck. Plastic waste is an extensively researched topic. I don't have access to  Jambeck et al., Science 2015, but I did find a graphic and summary. The numbers are all year-long totals for 2010.

The study's estimated range of plastic entering the ocean is 4.8 million to 12.7 million metric tons (MMT).

For the United States we can find some other figures to try to complete the picture. According to the EPA, in 2012, the US generated 251 MMT of municipal solid waste (MSW). Of that, 11.7% was burned, 34.5% was recovered by some sort of recycling, and 53.8% was discarded (Fig. 4). Plastics compose 12.7% of pre-recycling waste but 17.6% of post-recycling waste. Biodegradables (here I'm using food, paper, yard trimmings, and wood, but not textiles) consist of 61.7% of trash before recycling and 52.8% after.

So if we assume those ratios can be applied to the plastics sent to the ocean (8 MMT) you get the following:

Assuming global ocean waste has a similar composition as US
non-recycled waste, there are 63 MMT garbage entering the sea, of
which 39 MMT are biodegradable.
Assuming global ocean waste has a similar composition as US recycled
waste, there are 45 MMT garbage entering the sea of which 24 MMT are
biodegradable.


How to perform precipitation data analysis?

Date/timestamps are tricky to convert without further information; are the values you show days (unlikely, if 990555 is your date/time value), hours, seconds? See if you can figure out the system used (either by knowing which date your timestamp is supposed to represent, or looking at the step sizes for the data); this will generally give you an idea of what is being represented, and how to convert to an actual date.
Coordinate and long/lat are basically the same thing, only built up from decimals or hours/minutes (e.g. 0.5 representing 30 minutes). Conversion can be found http://transition.fcc.gov/mb/audio/bickel/DDDMMSS-decimal.html, for instance. Mind that other coordinate systems are also possible, which will make the conversion different; again, this is important to figure out before you can convert your data.
Comparison options will depend on: 1) whether your data corresponds (do you have measurements on the same date/time, as well as the same location?), 2) what you are interested in.


Is the magma in one volcano different from the magma in every other volcano?

In keeping with your Lord of the Rings inspiration, the first reference is from New Zealand, where the Lord of the Rings movies were made.

There are three main types of magma that volcanoes currently produce: basalt, andesite and rhyolite.

Basalt magma has a high temperature, around 1200ºC, it is poor in silica, has a low viscosity and a low gas content. When basalt erupts it produces a flowing magma.

Andesite magma has a mid range temperature, between 800ºC and 1000ºC, it also has a mid range silica content and moderate viscosity and gas content. When andesite erupts it flows but it is also moderately explosive.

Rhyolite magma has a low temperature, between 750ºC and 850ºC, it is silica rich and it has a very high viscosity and high gas content. When it erupts it is very explosive.

Other forms of magma which are much rarer are carbonatite melts and komatiite melts. Carbonatite melts may be cool, as low as 600ºC, whereas komatiite may have been as hot as 1600ºC.

Unlike the other forms of magma that are composed of silicate minerals, carbonate melts are composed of carbonates and can be confused with marble and may have to be geochemically analysed.

Most komatiites are very old, up to  4 billion years old. It is speculated that komatiite magma formation was possible when the Mantle was at least 500ºC hotter.


Can two earthquakes happen at the same time?

The 2016 paper "A case for historic joint rupture of the San Andreas and San Jacinto faults" reports of research suggesting that simultaneous large earthquakes occurred in 1812 in California, the researchers used

  dynamic rupture modeling to show that paleoseismic and historic observations associated with the earthquake of 8 December 1812 can be explained by joint rupture of the SAF and SJF.

(SAF = San Andreas Fault and SJF = San Jacinto Fault)

But the author stresses that what they have is a model, rather than a certainty.

Alot of research centres around the notion of 'near-simultaneous earthquakes', such as the 2009 South Pacific earthquake, as described in the article "Double Shake: Multiple, Nearly Simultaneous Earthquakes Triggered Deadly 2009 Tsunami" where studies suggest that at least 2 quakes of similar magnitude occurred within 50km of eachother, separated by minutes - another similar study suggests that one of the quakes 'obscured' another nearby rupture of equal or higher magnitude.

Italy is another place where simultaneous or near-simultaneous earthquakes seem to occur and resulted in several studies, one of which being reported in the article "Likely near-simultaneous earthquakes complicate seismic hazard planning for Italy", stating that

  It's very important to consider this scenario of earthquakes, occurring possibly seconds apart, one immediately after another

Stating that this scenario would have an 'amplification' effect of the the effects of the shhaking (hence, the researchers' concern).  A particular example they cite is

  The 1980 Irpinia earthquakes included a sequence of three events, occurring at intervals within 20 seconds of each other.

Another compelling example, reported in the article "Sumatran strike-slip earthquakes challenge seismologists" that occurred in April, 2012 - a strike-slip fault induced quake of a magnitude of 8.6 on the richter Scale, one of the theories for the great magnitude is explained as

  Another apparent reason for the large magnitude, says Miaki Ishii, a sesimologist at Harvard University, is that multiple faults appear to have slipped almost simultaneously, creating a composite earthquake. “If it was just a single fault activation, it wouldn’t have been large as 8.6.

An important note the Harvard seismologist makes, that essentially answers your question regarding simultaneous (and near-simulatneous earthquakes), is that observations of this kind of fault activation, which is described as "a cascading failure of faults" are seen in a lot of large earthquakes.


Are there sources that offer derivative climate change data?

Since you comment on statistics provided during sport events, I should point out that this method is not scientifically sound. The reason is that for any given data you will find something that will make this dataset unique or "the first of this kind in recorded history". For a light take on this, refer to this XKCD comic.

What is methodically required is that first the criteria are defined and only then the data are evaluated. Weather services will typically publish things such as

Ranking average temperature within a calendar month (e.g. this July was the third hottest in recorded history (example is purely fictional)) at a certain location
Ranking of daily minimum/maximum temperature at some location (e.g. this was the coldest day ever measured)

Details on this will vary from country to country. There is also a wide range of measurement data or derived data for experts to analyze. Also, weather services will engage in studies about the impact of climate change.


How can the 'crystal cleavage' of apatite have a four-digit number?

This is not a four- digit number but four separare numbers called Bravais-Miller indices.  Bravais-Miller indices descrive the orientation of a crystal plane relative to the symmetry axes of a crystal, as described in Wikipedia.  Put very briefly, a zero index means the plane is parallel to that axis, while nonzero indices encode the relative values of the intercepts on axes to which the plane is not parallel.  These pieces of information about parallel and nonparallel axes, together, specify the orientation of any plane that passes through the lattice points of a crystal.
In cubic crystals there are three principal, fourfold axes and thus you render three (not two) numbers for the Bravais-Miller indices of a plane; this is adapted to most other crystal systems.  But, exceptionally for hexagonal and rhombohedral systems, there are four symmetry axes; three of them in the hexagonally packed basal plane and the fourth perpendicular to them along the sixfold or theefold rotational axis.  Thus four indices are commonly used for that case.  The illustration below (Source) gives some commonly encountered planes in hexagonal crystals.

Putting the first three axes into the same plane means the intercept designations on these axes must be dependent on each other; in fact those three numbers should add up to zero.  Thus $[1010]$ is not correct; it should be $[10(-1)0]$ or using the more common notation for a negative index, $[10\overline10]$.  As shown in the above illustration, physically this corresponds to the lateral face of a hexagonal prism.


Is it possible for rivers to freeze completely and stop flowing?

I am interpreting your question as referring to rivers with flowing water freezing as as opposed to glaciers, which are already frozen.

Under current climatic conditions, small rivers can freeze throughout: from bank to bank, surface to river bed. I'm avoiding using the word solid as some people use that word when a river's surface has frozen from bank to bank.

Large rivers do not freeze "through out" because,

  Water, ice, and snow are good insulators and poor conductors of heat.
  The portions of a lake or river that are exposed to the cold winter
  air will freeze into ice and this ice insulates the water below from
  further rapid freezing. Also contributing to the prevention of bodies
  of water freezing solid is an interesting characteristic of water.
  Like most other forms of matter, water become denser as it cools, but
  beginning at about 39°F (4°C) something odd happens - water begins to
  lose density as it gets colder, becoming least dense when it freezes
  into ice. This is why ice floats. As water becomes colder it rises to
  the top, eventually freezing to the layers of ice that are already
  there. Insulation of the water beneath is increased as the ice
  thickens so cooling of the water beneath slows.

From The Great Land of Alaska: Why don't lakes and rivers freeze solid?

Also, while water is flowing its potential energy is constantly being converted to heat energy that resists freezing on the molecular level and subsequent crystallization.

For flowing water to freeze, the temperature would have to be exceptionally cold.


I highly recommend Climate: A Very Short Introduction and Climate Change: A Very Short Introduction, both by Mark Maslin and published through Oxford U Press's highly-regarded VSI series. I use both books when teaching college-level classes where an understanding of climate and climate change are important to the subject matter but are not the sole focus of the class.


There are many generalized references, such as
http://moe.met.fsu.edu/~rhart/papers-hart/2006Hart.pdf
https://en.wikipedia.org/wiki/Tropical_cyclone
http://www.aoml.noaa.gov/hrd/tcfaq/tcfaqD.html
But I think the best is Kerry Emmanuel's presentation:
http://www3.nd.edu/~its/Emanuel.pdf
Is this sufficient detail for you? If not, then you probably need to do a course in tropical meteorology.


Are the cores of every mountain range igneous?

Many mountain ranges do not have igneous cores. The front ranges of the Rocky Mountains in British Columbia are created by thrust faults that push sedimentary strata up to form the mountains. The driving force for this motion is a subduction zone located 100's of kilometres to the west. I believe that the Himalayas mountains are formed in a similar fashion.

See the following Wikipedia article: Geology of the Rocky Mountains


Lightning activity day curve - why it has high and narrow peak?

I think the simple answer to your question is that sunlight widens the potential area for storms by producing a better convective environment, whereas nocturnal storms are highly localized based on climatological factors.
While a minority of storms do occur overnight due to local mesoscale features such as nocturnal low-level jets, the majority of storms will occur because of convective forcing. To have a convective environment, you have to have a parcel of air that is warmer than that of the environment it is traveling through, and that is what gives you lift. The easiest way for that to happen is to have parcels rise up from the ground at the peak heating of the day while the ground is much warmer than the air above it.
In an older (and still infinitely useful) thought process of meteorology, there is a temperature known as the "convective temperature" that can be gotten from a Skew-T diagram. It takes into account the dewpoint and vertical temperature profile of the atmosphere and produces a temperature at which the surface level has to get to in order to set off thunderstorms. The best way to get to and beyond that temperature is through the heating of the sun. Additionally, when the air is warmed through heating from the sun it makes the environment ripe for convective initiation through triggers such as fronts.


Normally in the absence of rotation, the natural tenancy of gravity is to pull the Earth together in the shape of a sphere.

However the Earth in fact bulges at the equator, and the diameter across the equatorial plane is 42.72 km more than the diameter from pole to pole.

This is due to the rotation of the Earth.

As we can see in the image above, the spinning disk appears to bulge at the points on the disk furthest from the axis of rotation.

This is because in order for the particles of the disk to remain in orbit, there must be an inward force, known as the centripetal force, given by:

$$F = \frac{mv^2}{r},$$

where $F$ is the force, $m$ is the mass of rotating body, $v$ is the velocity and $r$ is the radius of particle from the axis of rotation.

If the disk is rotating at a given angular velocity, say $\omega$, then the tangential velocity $v$, is given by $v = \omega r$.

Therefore,

$$F = m\omega^2r$$

Therefore the greater the radius of the particle, the more force is required to maintain such an orbit.

Therefore particles on the Earth near the equator, which are farthest from the axis of rotation, will buldge outwards because they require a greater inward force to maintain their orbit.

Additional details for more mathematically literate now that mathjax is enabled:

The net force on an object rotating around the equator with a radius $r$ around a planet with a gravitational force of $\frac{Gm_1m_2}{r^2}$ is the centripetal force given by,

$$F_{net} = \frac{Gm_1m_2}{r^2} - N = m\omega^2r,$$ where $N$ is the normal force.

Re-arranging the above equation gives:

$$N = \frac{Gm_1m_2}{r^2} - m\omega^2r$$

The normal force here is the perceived downward force that a rotating body observers.  The equation shows that the perceived downward force is lessened due to the centripetal motion.  The typical example to illustrate this is there is an appearance of 0 gravity in a satellite orbiting the Earth, because in this situation the centripetal force is exactly balanced by the gravitational force.  On Earth however, the centripetal force is much less than the gravitational force, so we perceive almost the whole contribution of $mg$.

Now we will examine how the perceived gravitational force differs at different angles of latitude.  Let $\theta$ represent the angle of latitude.  Let $F_G$ be the force of gravity.

In vector notation we will take the $j$-direction to be parallel with the axis of rotation and the $i$-direction to be perpendicular with the axis of rotation.

In the absence of the Earth's rotation,

$$F_G = N = (-\frac{Gm_1m_2}{r^2}\cos\theta)\tilde{i} + (-\frac{Gm_1m_2}{r^2}\sin\theta)\tilde{j}$$

It is easily seen that the above equation represents the perceived force of gravity in the absence of rotation.  Now the centripetal force acts only in the i-direction, since it acts perpendicular to the axis of rotation.

If we let $R_{rot}$ be the radius of rotation, then the centripetal force is $m_1\omega^2R_{rot}$, which for an angle of latitude of $\theta$ corresponds to $m_1\omega^2r\cos{\theta}$

$$N = (-\frac{Gm_1m_2}{r^2} + m_1\omega^2r)\cos{\theta}\tilde{i} + (-\frac{Gm_1m_2}{r^2})\sin{\theta}\tilde{j}$$

By comparing this equation to the case shown earlier in the absence of rotation, it is apparent that as $\theta$ is increased (angle of latitude), the effect of rotation on perceived gravity becomes negligible, since the only difference lies in the $x$-component and $\cos\theta$ approaches 0 as $\theta$ approaches 90 degrees latitude.  However it can also be seen that as theta approaches 0, near the equator, the $x$-component of gravity is reduced as a result of the Earth's rotation.  Therefore, we can see that the magnitude of $N$ is slightly less at the equator than at the poles.  The reduced apparent gravitational pull here is what gives rise to the slight bulging of the Earth at the equator, given that the Earth was not originally as rigid as it is today (see other answer).


Why do certain areas on Earth have a higher or lower air pressure at sea level?

By way of analogy consider a hot air balloon. The balloon encloses some air. As the air is heated, via massive gas burners, the air in the balloon becomes less dense compared to the air outside the balloon and eventually the less dense air in the balloon rises, lifting the balloon into the air.

Atmospheric air in contact with the Earth does the same thing. Air is differentially heated and cooled due to the effects of the Sun, clouds, cold air injected from polar regions and warm or hot air injected from equatorial regions. This affects the energy of the air and its density. Air density is also affected by moisture; very little over dry hot deserts and more over oceans, lakes, large water reservoirs and forests, due to transpiration from trees.

The temperature differentials result in relatively warmer and cooler spots within the air in contact with the Earth's surface and above it. Air in the relatively warmer spots rises. The height to which it rises will in part be affected by the amount of heat it contains when it starts to rise.

The surface of the Earth immediately below the column of rising air experiences less air pressure than neighboring regions, hence such regions have low air pressure. As the air rises it cools. Eventually, the air falls back down. The area of the Earth's surface below the falling column of air has a higher pressure relative to its neighboring areas, giving rise to high pressure systems.

The seasonal variation of the general locations of high and low pressure systems are due to the differences in the thermal energy of the air, which in turn is determined by the sources of heat and what might be inhibiting heating.

Edit: In Reply to Additional Questions in the Comment Section

If you look at the pictures you provided the links for in your question you'll see that during July there is a low pressure zone over North America in addition to the much deeper low pressure zone over north eastern Asia. Additionally, the north-east Asian low pressure zone extends into eastern Europe and north Africa. The high pressure zones, in the northern hemisphere are effectively “islands” over the Atlantic and Pacific Oceans centered around 30 to 40 degrees latitude. Apart from western Europe and parts of the eastern US coast, northern hemisphere landmasses are under low pressure.

When you look of the picture for January there is a continuous high pressure zone extending from North American to east Asia and into north Africa. There is even a high pressure zone over Greenland. The regions experiencing low pressure are the most of oceans and the equatorial zones – tropical and sub-tropic part of the Earth.

July in the northern hemisphere is the start of the summer and January is well into winter. By July, the landmasses have been accumulating heat from the Sun, since the end of winter, and warming the air above it causing the air to rise and the air pressure to be lower.

Conversely, by January, the landmasses have cooled so they are not heating the air above them. However, air from the northern equatorial region is rising and due to Hadley cells the air falls back down causing the high pressure zones.


How to estimate dispersion in stratified flows

There are lots of studies considering Lagrangian dispersion. One critical aspect is the addition of random displacement to the deterministic particle track in order to consider subgrid-scale processes. Your measure of dispersion seems acceptable except for the fact that it might be dependent on the resolution of your flow field. In order to compare your dispersion with other areas or times, you might need to scale it by the horizontal diffusivity of the flow. Some studies that could be helpful are Mariano et al. (2002), Proehl et al. (2005), Lynch & Smith (2010).


Can a Humidity Differential move PM2.5 Pollution?

Humidity or recent rain plays a huge difference in air pollution. Seattle has less air pollution, because the effect of heavy rain and water accumulating on particles 'wash" the air. In hotter, drier Los Angeles the pollution stays in the air longer because there's less moisture to weigh it down. Mold, spores, dust and allergens do thrive in humidity but those aren't Pollutants in the classical industrial sense.


Odd structures in 66 year NCEP daily temperature reanalysis

It looks like a Gibbs oscillation, a basic feature of spectral analysis. In a spectral atmospheric model this means that near high orography artificial surface waves exist which may reflect in different variables. They are usually not considered to affect meteorology, however.

onlinelibrary.wiley.com/doi/10.1029/2010JC006927/full
http://journals.ametsoc.org/doi/abs/10.1175/1520-0442%281994%29007%3C1169%3AROTGOI%3E2.0.CO%3B2

This is from Bacmeister, Julio T. "Weather Prediction Models." Climate Change Modeling Methodology. Springer New York, 2012. 89-114.


The place is called Urðarháls. I could not find much information about it in the scientific literature... It is mentioned in Sigmarsson & Halldórsson (2015): they say it's an interglacial basaltic shield volcano, possibly associated with the Askja volcanic system. The fact that the volcano was eroded by glaciers probably explains the colour difference with the surrounding "fresh", postglacial lavas.

The crater looks like a pit crater to me: it probably collapsed when lava was drained somewhere else, leaving an empty chamber beneath it. Another good example of pit crater is the Dolomieu, on Piton de la Fournaise, which collapsed in 2007. Look at Staudacher et al. (2009): compare figure 3, before the collapse, and figure 11, after.

Note that the authors use the term "caldera", which is loosely defined... What Wikipedia calls a non-explosive caldera would be referred to as a pit crater by some. I guess the two terms kind of overlap.


July/August hottest months (northern hemisphere): because of continued warming or other effects?

The amount of surface heating from the sun is a function of time of year and latitude.  You are aware of the dependence on the time of year with the sun over the equator at the equinoxes and ~ $\pm$23$^\circ$ N at the solstices.  The varying position of the sun overhead means the projection of a solid angle from the sun onto the surface of the earth will vary as well.  This just means that when the sun is low, the energy in a "beam" of sunlight is spread over a very large area and warming will be reduced.  This is why a bright sunny day in the winter cannot provide the same heating as the bright sunny day in the summer.

Surface energy loss is a function of the temperature of the surface, and atmospheric energy loss is a function of the local atmospheric temperature.  There are some complications here, namely clouds and greenhouse gases that prevent some radiative losses.

At the summer solstice when days are long and the sun is at its highest it is easy to understand that we are getting more energy than we are losing, and the days should be warm.  What isn't so apparent is that after the days start shortening and the sun lowering in the sky that the days continue to warm.  This is simply because we are still getting more energy than we are losing.  It isn't until the energy losses (which happen 24 hours a day, regardless of day/night) finally overcome our energy gains (which only happen when the sun is out) that the days will start to cool.

From www.atmos.washington.edu

This image is from the northern hemisphere, but it is unclear what latitude it is for.  The summer solstice is the maximum in solar insolation and the winter solstice the minimum.  Radiative losses increase with temperature, and it is the point at which temperature has risen enough such that the loss is equal to the (diminishing) solar input.  This is where the maximum temperature will occur.  The lag between the solstice and the max temperature will vary with latitude.

As mentioned in a comment in the other answer, large bodies of water exaggerate this seasonal lag in temperature.  This is for the same reasons as for land, with the added effect of the large heat capacity of water (about 3x that of land).

You see the same effect in daytime maximum and minimum temperatures where (barring anything but solar influence) the daily max is often in the late afternoon and the daily min is often just before sunrise.  This is the same reasoning as above, just on a daily scale rather than seasonal.  The sun is overhead at solar noon (this varies with local noon based on longitude, time zone (daylight saving time)) but continues to provide solar heating after solar noon.  It isn't until the radiative losses overcome the radiative gains (afternoon to late afternoon) that the temperature will drop.  Likewise when the sun goes down temperatures will cool down until the sum comes back up.

From www.vsc.edu


Considering there are evaporation ponds worldwide (San Francisco Bay is full of them, and Morton used to, and may still, have the majority) used for harvesting sea salt, it's doubtful that any salt deposits would end up in the Martian atmosphere. And the atmosphere of Mars is too thin to hold salt blown from existing salt deposits, so salt blown into the atmosphere by Martian dust storms would quickly settle out of the atmosphere.


What do opaque rims on biotite in a volcanic rock mean?

There are several options.

During decompression, biotite is no longer stable and the hydrogen volatilises, leaving behind fine-grained intergrowth of oxide and silicate minerals.
Oxidation of the rims during exposure of the lava to the atmosphere. Higher Fe3+ contents would make the biotite darker.

It is impossible to tell without a detailed electron microscopy analysis. However, my guess it that it is option 1.


Why is it good scientific practice to 'build' a 'control Earth' from models, and where else do we 'build' controls?

It's true that, usually, when data is collected in an experiment scientists have a control, and very often not having a control results in a flawed experiment - that is, an experiment from which less conclusions can be drawn.

Experiments are a very efficient way to gather high quality data, but in some fields they might even be impossible. However, experiments aren't the only way to get knowledge and they aren't mandatory to make science.

In some fields experiments are quite easy and therefore most research is based in experiments. For example, it's usually easy for chemist to test the way substances react by making experiments.

In other fields some questions can't be resolved by direct experiments due to practical or ethical reasons. In a known textbook example, sociologists are interested in what circumstances cause suicide rates to rise or drop, but ethics prevents them from performing an experiment by submitting a sample of people to circumstances supposed to induce suicide and compare suicide rate of this sample with suicide rate in a control sample. Therefore, sociologist need to draw conclusions from observational data - that is, observing real population under natural circumstances they can't adjust - or from experiments of related phenomena that can be performed without ethical concerns.

We in Earth sciences face a similar problem: some experiments can't be done because of scale or just because we just have an only Earth. For example, how do we know that rivers cause deltas? Ideally, we'd like to do an experiment by selecting several coast tracts, putting rivers in a randomly chosen sample of them, waiting a few millions of years and comparing evolution of the coast tracts with and without rivers. We can't do this experiment, but it doesn't prevent geologists to have learned a lot about deltas, because we have a lot of data from observation of naturally occurring deltas, from small scale experiments, and from study of auxiliary sciences (physics, hydraulics, etc.).

Climate is similar to deltas. Just as we can experiment with setting and removing rivers, we can't change CO2 levels of the whole atmosphere to measure what happens, but we can observe what actually happens, search for geological register of what happened in the past, do a lot of small scale experiments, and use our knowledge of basic sciences and draw conclusions about climate evolution from them.

Clearly, interpretation of that data is not as straightforward as data from a big experiment would be, but it is still possible and useful. In fact, it's the way most of current knowledge in many fields has been built.

All that without needing a random sample of Earths nor a control Earth.


Polar Ice caps are melting? Questions on enviromental impact

I think you misinterpret the article you cited. In the article it is stated that:

  The melting of the polar ice-caps has
  an effect "the equivalent of about 20 years of additional CO$_2$ being
  added by man"

This is due to the energy in sunlight which is no longer reflected by the white ice and snow of the polar caps. This energy will be partly absorbed by the darker surface of the ocean or land which will be underneath the ice-caps. This absorption of energy (instead of reflection) has an effect which is equal to "the equivalent of about 20 years if additional CO$_2$ being added by mankind".

There probably are models that can tell how much CO$_2$ can be absorbed by trees. However, an ecosystem which is in balance (e.g. a full grown forest) doesn't absorb that much CO$_2$ anymore. This is because the growth of new trees is equal to the dying and decomposition of old trees (in balance). Only a little part might be stored in the soil.

An increase of CO$_2$ might increase the growth rate of trees due to in increase of effectiveness of photosynthesis. (Stomata will have to be open less longer to require the same amount of CO$_2$ and therefore trees will lose less water for example).

Our ocean does absorb CO$_2$ as well. Algea, phytoplankton, and chemical process all make this happen. What you mean with recycle -- as well I'm not sure.