query: Warmer seasons or triennial phases are followed by an atmosphere that is rich in CO2, reflecting the gas solving or exsolving from water, and not photosynthesis activity.

positive: Water Water is a transparent and nearly colorless chemical substance that is the main constituent of Earth 's streams , lakes , and oceans , and the fluids of most living organisms . Its chemical formula is H2O , meaning that its molecule contains one oxygen and two hydrogen atoms , that are connected by covalent bonds . Water strictly refers to the liquid state of that substance , that prevails at standard ambient temperature and pressure ; but it often refers also to its solid state ( ice ) or its gaseous state ( steam or water vapor ) . It also occurs in nature as snow , glaciers , ice packs and icebergs , clouds , fog , dew , aquifers , and atmospheric humidity .   Water covers 71 % of the Earth 's surface . It is vital for all known forms of life . On Earth , 96.5 % of the planet 's crust water is found in seas and oceans , 1.7 % in groundwater , 1.7 % in glaciers and the ice caps of Antarctica and Greenland , a small fraction in other large water bodies , and 0.001 % in the air as vapor , clouds ( formed of ice and liquid water suspended in air ) , and precipitation . Only 2.5 % of this water is freshwater , and 98.8 % of that water is in ice ( excepting ice in clouds ) and groundwater . Less than 0.3 % of all freshwater is in rivers , lakes , and the atmosphere , and an even smaller amount of the Earth 's freshwater ( 0.003 % ) is contained within biological bodies and manufactured products . A greater quantity of water is found in the earth 's interior .   Water on Earth moves continually through the water cycle of evaporation and transpiration ( evapotranspiration ) , condensation , precipitation , and runoff , usually reaching the sea . Evaporation and transpiration contribute to the precipitation over land . Large amounts of water are also chemically combined or adsorbed in hydrated minerals .   Safe drinking water is essential to humans and other lifeforms even though it provides no calories or organic nutrients . Access to safe drinking water has improved over the last decades in almost every part of the world , but approximately one billion people still lack access to safe water and over 2.5 billion lack access to adequate sanitation . There is a clear correlation between access to safe water and gross domestic product per capita . However , some observers have estimated that by 2025 more than half of the world population will be facing water-based vulnerability . A report , issued in November 2009 , suggests that by 2030 , in some developing regions of the world , water demand will exceed supply by 50 % .   Water plays an important role in the world economy . Approximately 70 % of the freshwater used by humans goes to agriculture . Fishing in salt and fresh water bodies is a major source of food for many parts of the world . Much of long-distance trade of commodities ( such as oil and natural gas ) and manufactured products is transported by boats through seas , rivers , lakes , and canals . Large quantities of water , ice , and steam are used for cooling and heating , in industry and homes . Water is an excellent solvent for a wide variety of chemical substances ; as such it is widely used in industrial processes , and in cooking and washing . Water is also central to many sports and other forms of entertainment , such as swimming , pleasure boating , boat racing , surfing , sport fishing , and diving .

positive: Carbon dioxide Carbon dioxide ( chemical formula ) is a colorless gas with a density about 60 % higher than that of air ( 1.225 g/L ) that is odorless at normally encountered concentrations . Carbon dioxide consists of a carbon atom covalently double bonded to two oxygen atoms . It occurs naturally in Earth 's atmosphere as a trace gas at a concentration of about 0.04 percent ( 400 ppm ) by volume . Natural sources include volcanoes , hot springs and geysers , and it is freed from carbonate rocks by dissolution in water and acids . Because carbon dioxide is soluble in water , it occurs naturally in groundwater , rivers and lakes , ice caps , glaciers and seawater . It is present in deposits of petroleum and natural gas .   As the source of available carbon in the carbon cycle , atmospheric carbon dioxide is the primary carbon source for life on Earth and its concentration in Earth 's pre-industrial atmosphere since late in the Precambrian has been regulated by photosynthetic organisms and geological phenomena . Plants , algae and cyanobacteria use light energy to photosynthesize carbohydrate from carbon dioxide and water , with oxygen produced as a waste product .   Carbon dioxide is produced by all aerobic organisms when they metabolize carbohydrates and lipids to produce energy by respiration . It is returned to water via the gills of fish and to the air via the lungs of air-breathing land animals , including humans . Carbon dioxide is produced during the processes of decay of organic materials and the fermentation of sugars in bread , beer and winemaking . It is produced by combustion of wood and other organic materials and fossil fuels such as coal , peat , petroleum and natural gas .   It is a versatile industrial material , used , for example , as an inert gas in welding and fire extinguishers , as a pressurizing gas in air guns and oil recovery , as a chemical feedstock and in liquid form as a solvent in decaffeination of coffee and supercritical drying . It is added to drinking water and carbonated beverages including beer and sparkling wine to add effervescence . The frozen solid form of , known as `` dry ice '' is used as a refrigerant and as an abrasive in dry-ice blasting .   Carbon dioxide is the most significant long-lived greenhouse gas in Earth 's atmosphere . Since the Industrial Revolution anthropogenic emissions - primarily from use of fossil fuels and deforestation - have rapidly increased its concentration in the atmosphere , leading to global warming . Carbon dioxide also causes ocean acidification because it dissolves in water to form carbonic acid .

positive: Greenhouse gas A greenhouse gas ( abbrev . GHG ) is a gas in an atmosphere that absorbs and emits radiation within the thermal infrared range . This process is the fundamental cause of the greenhouse effect . The primary greenhouse gases in Earth 's atmosphere are water vapor , carbon dioxide , methane , nitrous oxide , and ozone . Without greenhouse gases , the average temperature of Earth 's surface would be about -18 ° C , rather than the present average of 15 ° C . In the Solar System , the atmospheres of Venus , Mars and Titan also contain gases that cause a greenhouse effect .   Human activities since the beginning of the Industrial Revolution ( taken as the year 1750 ) have produced a 40 % increase in the atmospheric concentration of carbon dioxide , from 280 ppm in 1750 to 406 ppm in early 2017 . This increase has occurred despite the uptake of a large portion of the emissions by various natural `` sinks '' involved in the carbon cycle . Anthropogenic carbon dioxide emissions ( i.e. , emissions produced by human activities ) come from combustion of fossil fuels , principally coal , oil , and natural gas , along with deforestation , soil erosion and animal agriculture .   It has been estimated that if greenhouse gas emissions continue at the present rate , Earth 's surface temperature could exceed historical values as early as 2047 , with potentially harmful effects on ecosystems , biodiversity and the livelihoods of people worldwide . Recent estimates suggest that on the current emissions trajectory the Earth could pass a threshold of 2 ° C global warming , which the United Nations ' IPCC designated as the upper limit to avoid `` dangerous '' global warming , by 2036 .

positive: Global warming Global warming , also referred to as climate change , is the observed century-scale rise in the average temperature of the Earth 's climate system and its related effects . Multiple lines of scientific evidence show that the climate system is warming . Many of the observed changes since the 1950s are unprecedented in the instrumental temperature record which extends back to the mid 19th century , and in paleoclimate proxy records over thousands of years .   In 2013 , the Intergovernmental Panel on Climate Change ( IPCC ) Fifth Assessment Report concluded that `` It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century . '' The largest human influence has been emission of greenhouse gases such as carbon dioxide , methane and nitrous oxide . Climate model projections summarized in the report indicated that during the 21st century the global surface temperature is likely to rise a further 0.3 to for their lowest emissions scenario and 2.6 to for the highest emissions scenario . These findings have been recognized by the national science academies of the major industrialized nations and are not disputed by any scientific body of national or international standing .   Future climate change and associated impacts will differ from region to region around the globe . Anticipated effects include warming global temperature , rising sea levels , changing precipitation , and expansion of deserts in the subtropics . Warming is expected to be greater over land than over the oceans and greatest in the Arctic , with the continuing retreat of glaciers , permafrost and sea ice . Other likely changes include more frequent extreme weather events including heat waves , droughts , heavy rainfall with floods and heavy snowfall ; ocean acidification ; and species extinctions due to shifting temperature regimes . Effects significant to humans include the threat to food security from decreasing crop yields and the abandonment of populated areas due to rising sea levels . Because the climate system has a large `` inertia '' and greenhouse gases will stay in the atmosphere for a long time , many of these effects will not only exist for decades or centuries , but will persist for tens of thousands of years .   Possible societal responses to global warming include mitigation by emissions reduction , adaptation to its effects , building systems resilient to its effects , and possible future climate engineering . Most countries are parties to the United Nations Framework Convention on Climate Change ( UNFCCC ) ,  whose ultimate objective is to prevent dangerous anthropogenic climate change . Parties to the UNFCCC have agreed that deep cuts in emissions are required and that global warming should be limited to well below 2.0 C-change relative to pre-industrial levels , with efforts made to limit warming to 1.5 C-change .   Public reactions to global warming and concern about its effects are also increasing . A global 2015 Pew Research Center report showed a median of 54 % consider it `` a very serious problem '' . There are significant regional differences , with Americans and Chinese ( whose economies are responsible for the greatest annual CO2 emissions ) among the least concerned .

negative: Guard cell Guard cells are specialized cells in the epidermis of leaves , stems and other organs that are used to control gas exchange . They are produced in pairs with a gap between them that forms a stomatal pore . The stomatal pores are largest when water is freely available and the guard cells turgid , and closed when water availability is critically low and the guard cells become flaccid . Photosynthesis depends on the diffusion of carbon dioxide ( CO2 ) from the air through the stomata into the mesophyll tissues . Oxygen ( O2 ) , produced as a byproduct of photosynthesis , exits the plant via the stomata . When the stomata are open , water is lost by evaporation and must be replaced via the transpiration stream , with water taken up by the roots . Plants must balance the amount of CO2 absorbed from the air with the water loss through the stomatal pores , and this is achieved by both active and passive control of guard cell turgor and stomatal pore size .

negative: Recycled fuel Fuel made of residues as CO2 produced by using a primary fuel .   For example , CO2 pollution in the atmosphere , produced by petrol burning or other sources , can be extracted to produce fuel through an artificial photosynthesis based in nanotechnology , which helps to mitigate pollution , climate change and energy issues .

negative: Low-carbon emission The main components of automobile exhaust are carbon dioxide ( CO2 ) and water vapor ( H2O ) . Carbon dioxide is the most important anthropogenic greenhouse gas ( GHG ) and the most significant Greenhouse Gas emitted in the U.S. ( with 82-84 % of all U.S. emissions ) . Increases in carbon dioxide concentration are due primarily to fossil fuel use and land-use change .   The CO2 emission standards can be referred to the fuel or to the vehicle :   The European Union is moving towards fuel mandatory CO2 standards and USA has reflected it in the Greenhouse Gas Score .  There are information , but no mandatory , standards for CO2 limits in vehicle ( engine ) emissions , excepting some state regulations ( i.e. California ) . See hybrid vehicles .   CO2 mass emission in vehicles is measured in g/km ( g/mi * 0.621371192 = g/km ) .

negative: Chromatium okenii Chromatium okenii is a Gram-negative bacterium found in water . It belongs to the Purple sulfur bacteria . These bacteria are capable of photosynthesis and use Hydrogen sulfide ( H2S ) as an electron donor for CO2 reduction and so do not produce oxygen . This type of photosynthesis is called anoxygenic photosynthesis .  Chromatium okenii is anaerobic and the cells are slightly curved or straight rods .

negative: Spinodal decomposition Spinodal decomposition is a mechanism for the rapid unmixing of a mixture of liquids or solids  from one thermodynamic phase , to form two coexisting phases . As an example , consider a hot mixture of water and an oil . At high temperatures the oil and the water may mix to form a single thermodynamic phase in which water molecules are surrounded by oil molecules and vice versa . The mixture is then suddenly cooled to a temperature at which thermodynamic equilibrium favours an oil-rich phase coexisting with a water-rich phase . Spinodal decomposition then occurs when the mixture is such that there is essentially no barrier to nucleation of the new oil-rich and water-rich phases . In other words , the oil and water molecules immediately start to cluster together into microscopic water-rich and oil-rich clusters throughout the liquid . These clusters then rapidly grow and coalesce until there is a single macroscopic oil-rich cluster , the oil-rich phase , and a single water-rich cluster , the water-rich phase .   Spinodal decomposition can be contrasted with nucleation and growth . There the initial formation of the microscopic clusters involves a large free energy barrier , and so can be very slow , and may occur as little as once in the initial phase , not throughout the phase , as happens in spinodal decomposition .   Spinodal decomposition is of interest for two primary reasons . In the first place , it is one of the few phase transition in solids for which there is a complete quantitative theory . The reason for this is the inherent simplicity of the reaction . Since there is no thermodynamic barrier to the reaction inside of the spinodal region , the decomposition is determined solely by diffusion . Thus , it can be treated purely as a diffusional problem , and many of the characteristics of the decomposition can be described by an approximate analytical solution to the general diffusion equation .   In contrast , theories of nucleation and growth have to invoke the thermodynamics of fluctuations . And the diffusional problem involved in the growth of the nucleus is far more difficult to solve , because it is unrealistic to linearize the diffusion equation .   From a more practical standpoint , spinodal decomposition provides a means of producing a very finely dispersed microstructure that can significantly enhance the physical properties of the material .

negative: TEA laser A TEA laser is a gas laser energized by a high voltage electrical discharge in a gas mixture generally at or above atmospheric pressure . The most common types are CO2 lasers and Excimer lasers , both used extensively in industry and research . The acronym `` TEA '' stands for Transversely Excited Atmospheric .

negative: Pneumatocyst In phycology , a pneumatocyst is a floating structure that contains gas found on brown seaweed . A seaweed 's thallus may have more than one . They provide buoyancy to lift the blades toward the surface , allowing them to receive more sunlight for photosynthesis .   The proportion of gases in the pneumatocysts varies depending on the physiological status of the alga and the partial pressure of gases in the surrounding air or water . The pneumatocyst can hold O2 , CO2 , N2 , and CO. .

negative: Compensation point The ( light ) compensation point is the amount of light intensity on the light curve where the rate of photosynthesis exactly matches the rate of respiration . At this point , the uptake of CO2 through photosynthetic pathways is exactly matched to the respiratory release of carbon dioxide , and the uptake of O2 by respiration is exactly matched to the photosynthetic release of oxygen .   In assimilation terms , at compensation point , the net carbon dioxide assimilation is zero . Leaves release CO2 by photorespiration and day respiration , but CO2 is also converted into carbohydrate by photosynthesis . Assimilation is therefore the difference in the rate of these processes . At a normal partial pressure of CO2 ( 0.343 hPa in 1980 ) , there is an irradiation at which the net assimilation of CO2 is zero . For instance , in the early morning and late evenings , the compensation point may be reached as photosynthetic activity decreases and respiration increases . Therefore , the partial pressure of CO2 at the compensation point , also known as gamma , is a function of irradiation . The irradiation dependence of the compensation point is explained by the RuBP ( ribulose-1 ,5 - bisphosphate ) concentration . When the acceptor RuBP is in saturated concentration , gamma is independent of irradiation . However at low irradiation , only a small fraction of the sites on RuBP carboxylase-oxygenase enzyme ( Rubisco ) have the electron acceptor RuBP . This decreases the photosynthetic activity and therefore affects gamma . The intracellular concentration of CO2 affects the rates of photosynthesis and photo respiration . At higher carbon dioxide concentrations , the photosynthesis rate is higher , while at low CO2 concentrations , photo respiration is higher .

negative: Integrated fluorometer An integrated fluorometer is a system that measures the light reaction and the dark reaction of photosynthesis . Software allows combined operation of gas exchange measurement and chlorophyll fluorescence measurement of a leaf . These parameters are used to non-destructively measure the photosynthetic efficiency of plants . The use of an integrated chlorophyll fluorometer provides the opportunity to measure additional measuring parameters that allow for a more exact measurement of photosynthesis than with gas exchange alone . Advanced gas exchange instrumentation , by itself , is capable of measuring A/Ci curves , commonly used for plant characterization . `` A '' is the term for photosynthetic rate ( rate of CO2 exchange in the leaf chamber ) , and Ci is Sub-stomatal CO2 concentration or intracellular CO2 level within the leaf . When measured over a range of CO2 levels above and below ambient conditions , A/Ci curves become possible . With the addition of an integrated chlorophyll fluorometer , it becomes possible to measure more accurate A/CC curves , or photosynthetic rate at the site of carboxylation in chloroplasts . The integrated fluorometer allows measurement of mesophyll conductance , or the opposite of the resistance to CO2 transfer from intracellular air spaces to the site of carboxylation in chloroplasts . Various integrated chlorophyll fluorometer measuring protocols , such as the Laisk Protocol , the Kok protocol and the Yin Protocol are used to measure or estimate gm or mesophyll conductance . For example : the Laisk protocol allows the measurement of Γ * or compensation point , and Rd or respiration in the dark . Both values are required to calculate gm or mesophyll conductance and CC or CO2 at the site of carboxylation . Parameters typically measured by the gas exchange portion of the system include : `` A '' or photosynthetic rate , `` gs '' or stomatal conductance , `` Ci '' or sub stomatal CO2 concentration , and `` E '' or transpiration .

negative: Thomas D. Sharkey (plant biochemist) Thomas D. Sharkey is a plant biochemist who studies gas exchange between plants and the atmosphere . His research has covered ( 1 ) carbon metabolism of photosynthesis from carbon dioxide uptake to carbon export from the Calvin-Benson Cycle , ( 2 ) isoprene emission from plants , and ( 3 ) abiotic stress tolerance . Four guiding questions are : ( 1 ) how leaf photosynthesis affects plant yield , ( 2 ) does some carbon fixation follow an oxidative pathway that reduces sugar output but stabilizes photosynthesis , ( 3 ) why plants make isoprene , and ( 4 ) how plants cope with high temperature .

negative: Black-oil equations The black-oil equations are a set of partial differential equations that describe fluid flow in a petroleum reservoir , constituting the mathematical framework for a black-oil reservoir simulator .    The term black-oil refers to the fluid model , in which water is modeled explicitly together with two hydrocarbon components , one ( pseudo ) oil phase and one ( pseudo - ) gas phase .   This is in contrast with a compositional formulation , in which each hydrocarbon component ( arbitrary number ) is handled separately   The equations of an extended black-oil model are   where  is a porosity of the porous medium ,  is a water saturation ,  are saturations of liquid ( `` oil '' )  and vapor ( `` gas '' ) phases in the reservoir ,  are  Darcy velocities of the liquid phase , water phase and vapor phase in the reservoir .  The oil and gas at the surface ( standard conditions ) could be produced from both liquid and vapor phases existing at high pressure and temperature of reservoir conditions . This is characterized by the following quantities :   is an oil  formation volume factor  ( ratio of some volume of reservoir liquid  to the volume of oil at standard conditions  obtained from the same volume of reservoir liquid ) ,   is a water formation volume factor  ( ratio of volume of water at reservoir conditions to volume of water at standard conditions ) ,   is a gas formation volume factor  ( ratio of some volume of reservoir vapor  to the volume of gas at standard conditions obtained from the same volume of reservoir vapor ) ,   is a solution of gas in oil phase  ( ratio of volume of gas to the volume of oil at standard conditions  obtained from some amount of liquid phase at reservoir conditions ) ,   is a vaporized oil in gas phase  ( ratio of volume of oil to the volume of gas at standard conditions  obtained from some amount of vapor phase at reservoir conditions ) .

negative: Seaweed fuel Seaweed fuel or seaweed oil is an alternative to liquid fossil fuels that uses seaweed as its source of energy-rich oils . Like fossil fuel , seaweed fuel releases when burnt , but unlike fossil fuel , algae fuel and other biofuels only release recently removed from the atmosphere via photosynthesis as the seaweed or plant grew .   Unlike algae , seaweed does not require fresh water and can as such be grown in the sea .

negative: Perthite Perthite is used to describe an intergrowth of two feldspars : a host grain of potassium-rich alkali feldspar ( near K-feldspar , KAlSi3O8 , in composition ) includes exsolved lamellae or irregular intergrowths of sodic alkali feldspar ( near albite , NaAlSi3O8 , in composition ) . Typically the host grain is orthoclase or microcline , and the lamellae are albite . If sodic feldspar is the dominant phase , the result is an antiperthite .   The intergrowth forms by exsolution due to cooling of a grain of alkali feldspar with a composition intermediate between K-feldspar and albite . There is complete solid solution between albite and K-feldspar at temperatures near 700 ° C and pressures like those within the crust of the Earth , but a miscibility gap is present at lower temperatures . If an alkali feldspar grain with an intermediate composition cools slowly enough , K-rich and more Na-rich feldspar domains separate from one another . In the presence of water , the process occurs quickly .   When megascopically developed , the texture may consist of distinct pink and white lamellae representing exsolved white albite ( NaAlSi3O8 ) in pink microcline . The intergrowths in perthite have a great variety of shapes . If cooling is sufficiently slow , the alkali feldspar may exsolve to form separate grains with near-endmember albite and K-feldspar compositions . The largest documented single crystal of perthite was found in Hugo Mine in South Dakota and measured about 10.7 m x 4.6 m x 1.8 m.   The gem varieties of potassium feldspar , amazonite and moonstone are variant colored perthites .

negative: Vapor In physics a vapor ( American ) or vapour ( British ) is a substance in the gas phase at a temperature lower than its critical temperature , which means that the vapor can be condensed to a liquid by increasing the pressure on it without reducing the temperature . A vapor is different from an aerosol . An aerosol is a suspension of tiny particles of liquid , solid , or both within a gas .   For example , water has a critical temperature of 647 K , which is the highest temperature at which liquid water can exist . In the atmosphere at ordinary temperatures , therefore , gaseous water ( known as water vapor ) will condense into a liquid if its partial pressure is increased sufficiently .   A vapor may co-exist with a liquid ( or a solid ) . When this is true , the two phases will be in equilibrium , and the gas-partial pressure will be equal to the equilibrium vapor pressure of the liquid ( or solid ) .

negative: Solar radiation management Solar radiation management ( SRM ) projects are a type of climate engineering which seek to reflect sunlight and thus reduce global warming . Proposed examples include the creation of stratospheric sulfate aerosols . Their principal advantages as an approach to climate engineering is the speed with which they can be deployed and become fully active , their potential low financial cost , and the reversibility of their direct climatic effects . Solar radiation management projects could , for example , be used as a temporary response while levels of greenhouse gases can be brought under control by mitigation and greenhouse gas removal techniques . They would not reduce greenhouse gas concentrations in the atmosphere , and thus do not address problems such as ocean acidification caused by excess carbon dioxide ( CO2 ) .

negative: Estuarine acidification Estuarine acidification is a decrease in the pH of coastal marine ecosystems , specifically those of estuaries . pH change in estuaries is more complicated than in the open ocean due to direct impacts from land run-off and coastal current dynamics . Ocean acidification is the ongoing decrease in the pH of the Earth 's oceans , caused by the absorption of carbon dioxide ( CO2 ) from the atmosphere ( 0.1 units over the last century ) . The ocean absorbs 30-40 % of all CO2 emitted to the atmosphere ; this increase in aqueous carbon dioxide causes a decline in the pH of the ocean surface . As carbon dioxide combines with water , it releases protons ( hydrogen ions ) , based on the following equation :   CO2 + H2O ↔ H2CO3 ↔ HCO3 + H + ↔ CO3 + 2 H +

negative: Ethanol from coal Ethanol from coal is the ethanol produced using coal as its carbon source . The anaerobic bacterium Clostridium ljungdahlii produces ethanol and acetic acid from CO , CO2 , and H2 in synthesis gas . Early studies with C. ljungdahlii showed that relatively high concentrations of ethanol were produced . This process involves three main steps :  Gasification : Thermal gasification at temperatures of up to 2,200 ° F in a reducing , very low oxygen atmosphere transforms organic materials into simple CO , CO2 and H2 gases .  Fermentation : The acetogenic C. ljungdahlii convert the carbon monoxide into ethanol .  Distillation : Ethanol is separated from hydrogen and water .

negative: Calcium reactor __ NOTOC __   In marine and reef aquariums , a calcium reactor creates a balance of alkalinity . An acidic solution is produced by injecting carbon dioxide into a chamber with salt water and calcium rich media . The carbon dioxide lowers the pH by producing a solution high in carbonic acid , and dissolves calcium . The effluent is returned to the reef aquarium where the calcium is consumed by organisms , primarily corals when building skeletons . A calcium reactor is an efficient method to supply calcium to a reef aquarium . Reactors may be used in elaborate freshwater and brackish aquariums where freshwater clams and other invertebrates need a constant supply of calcium .   The reactor dissolves the calcium-laden media to provide bicarbonates HCO3 − ( alkalinity ) and calcium ( Ca + + ) ions at the sames rate as consumed during calcification . Effectively dissolving the media requires an acidic pH. Saltwater may have a pH of 7.8 or higher , so to reduce the pH carbon dioxide ( CO2 ) is used . The reaction formula is :   CaCO3 + H2O + CO2 < -- -- > Ca2 + + 2HCO3 −   Inside the reaction chamber , a calcium rich media ( aragonite ) , mainly CaCO3 , is forced into contact with water injected with carbon dioxide ( CO2 ) in order to create carbonic acid ( H2CO3 ) . This increases the solubility of the calcium carbonate . The reaction frees the calcium and carbonate , supplying the aquarium with water rich in Ca2 + and CO32 − , important for maintaining alkalinity and calcium levels .   The bubble counter measures carbon dioxide . The flow rate of carbon dioxide is monitored so that the dissolved gas goes into the solution , with a minimum unconsumed . A needle valve or solenoid valve regulates the CO2 bubble rate . Valves with precise adjustment abilities improve bubble control .   The feed pump controls the volume of water exchange . This is important because a high rate of water flow into the reactor reduces its efficiency , thus resulting in underproduction and a waste of CO2 .   Some reactors siphon water into the input of the reactor 's re-circulation pump . A potential complication is the medium in the reactor becoming compacted , increasing back pressure onto the pump and reducing water into the reactor . Placing a gate or needle valve on the reactor 's outlet side will improve flow characteristics compared to control from the inlet side .   A peristaltic pumps are effective operating against pressure , capable of supplying an adjustable and continuous flow over flow rates with minimal maintenance .   The pH control is connected to a probe in the reactor and adjusts the rate at which the calcium media dissolves . This probe monitors the pH level in the calcium reactor . The pH range for the typical calcium reactor is 6.5 - 6.8 . When the pH rises above a certain level , a valve opens , allowing carbon dioxide to enter the reactor . The control closes the valve as the pH falls below this level .   Some pH controllers have an interface for an air pump . This air pump is connected to an airstone in the sump or main tank . If the probe detects a low pH level , the pump activates . The bubbles raise the pH by dissipating the CO2 gas .

negative: Dole effect The Dole effect , named after Malcolm Dole , describes an inequality in the ratio of the heavy isotope 18O ( a `` standard '' oxygen atom with two additional neutrons ) to the lighter 16O , measured in the atmosphere and seawater . This ratio is usually denoted δ18O .   It was noticed in 1935 that air contained more 18O than seawater ; this was quantified in 1975 to 23.5 ‰ , but later refined as 23.88 ‰ in 2005 . The imbalance arises mainly as a result of respiration in plants and in animals . Due to thermodynamics of isotope reactions , respiration removes the lighter -- hence more reactive -- 16O in preference to 18O , increasing the relative amount of 18O in the atmosphere .   The inequality is balanced by photosynthesis . Photosynthesis emits oxygen with the same isotopic composition ( i.e. the ratio between 18O and 16O ) as the water ( H2O ) used in the reaction , which is independent of the atmospheric ratio . Thus when atmospheric 18O levels are high enough , photosynthesis will act as a reducing factor . However , as a complicating factor , the degree of fractionation ( i.e. change in isotope ratio ) occurring due to photosynthesis is not entirely dependent on the water drawn up by the plant , as fractionation can occur as a result of preferential evaporation of and other small but significant processes .

negative: Sudarsky's gas giant classification Sudarsky 's classification gas giants for the purpose of predicting their appearance based on their temperature was outlined by David Sudarsky and colleagues in the paper Albedo and Reflection Spectra of Extrasolar Giant Planets and expanded on in Theoretical Spectra and Atmospheres of Extrasolar Giant Planets , published before any successful direct or indirect observation of an extrasolar planet atmosphere was made . It is a broad classification system with the goal of bringing some order to the likely rich variety of extrasolar gas-giant atmospheres .   Gas giants are split into five classes ( numbered using Roman numerals ) according to their modeled physical atmospheric properties . In the Solar System only Jupiter and Saturn are within the Sudarsky classification , and both are Class I.  The appearance of planets that are not gas giants can not be predicted by the Sudarsky system , for example terrestrial planets such as Earth , HD 85512 b ( 3.6 Earth masses ) and OGLE-2005-BLG-390Lb ( 5.5 Earth masses ) , or ice giants such as Uranus ( 14 Earth masses ) and Neptune ( 17 Earth masses ) .

negative: Homoiohydry Homoiohydry is the capacity of plants to regulate , or achieve homeostasis of , cell and tissue water content . Homoiohydry evolved in land plants to a lesser or greater degree during their transition to land more than 500 million years ago , and is most highly developed in the vascular plants . It is the consequence of a suite of morphological innovations and strategies that enable plant shoots exploring aerial environments to conserve water by internalising the gas exchange surfaces , enclosing them in a waterproof membrane and providing a variable aperture control mechanism , the stomatal guard cells , which regulate the rates of water transpiration and CO2 exchange . In vascular plants , water is acquired from the soil by roots and transported via the xylem to aerial portions of the plant . Water evaporation from the aerial surfaces of the plant is controlled by a waterproof covering of cuticle . Gas exchange with the atmosphere is controlled by stomata , which can open and close to control water loss , and diffusion of carbon dioxide to the chloroplasts takes place in intercellular spaces between chlorenchyma cells in the stem or in the mesophyll tissue of the leaf .   The antonym of homoiohydry is poikilohydry , a condition in which plant water content is passively reduced or increased in equilibrium with environmental water status .

negative: Limescale Limescale is the hard , off-white , chalky deposit found in kettles , hot-water boilers and the inside of inadequately maintained hot-water central heating systems .   It is also often found as a similar deposit on the inner surface of old pipe and other surfaces where `` hard water '' has evaporated . In addition to being unsightly and hard to clean , limescale seriously impairs the operation or damages various components .   The type found deposited on the heating elements of water heaters has a main component of calcium carbonate . Hard water contains calcium ( and often magnesium ) bicarbonate or similar ions . Calcium salts , such as calcium bicarbonate and calcium carbonate are both more soluble in hot water than cold water . Thus , heating water does not cause calcium carbonate to precipitate per se . However , there is an equilibrium between dissolved calcium bicarbonate and dissolved calcium carbonate :   Ca2 + + 2HCO3 − ⇋ Ca2 + + CO32 − + CO2 + H2O   where the equilibrium is driven by the carbonate/bicarbonate , not the calcium . Note that the CO2 is dissolved in the water .   There is also an equilibrium of carbon dioxide between dissolved in water ( dis ) and the gaseous state ( g ) :  CO2 ( dis ) ⇋ CO2 ( g )   The equilibrium of CO2 also moves to the right towards gaseous CO2 when the water temperature rises . When water that contains dissolved calcium carbonate is warmed , CO2 is removed from the water as gas causing the equilibrium of bicarbonate and carbonate to shift to the right , increasing the concentration of dissolved carbonate . As the concentration of carbonate increases , calcium carbonate precipitates as the salt : Ca2 + + CO32 − ⇋ CaCO3 .   As new cold water with dissolved calcium carbonate/bicarbonate is added and heated , CO2 gas is removed , carbonate concentration increases , and more calcium carbonate precipitates .   Descaling agents are used to remove scale . Prevention of scale build-up relies on the technologies of water softening .

negative: Lime kiln A lime kiln is a kiln used for the calcination of limestone ( calcium carbonate ) to produce the form of lime called quicklime ( calcium oxide ) . The chemical equation for this reaction is   CaCO3 + heat → CaO + CO2   This reaction takes place at 900 ° C ( 1650 ° F ; at which temperature the partial pressure of CO2 is 1 atmosphere ) , but a temperature around 1000 ° C ( 1800 ° F ; at which temperature the partial pressure of CO2 is 3.8 atmospheres ) is usually used to make the reaction proceed quickly . Excessive temperature is avoided because it produces unreactive , `` dead-burned '' lime .   Slaked lime ( calcium hydroxide ) can be formed by mixing water with quicklime .

negative: Photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that can later be released to fuel the organisms ' activities ( energy transformation ) . This chemical energy is stored in carbohydrate molecules , such as sugars , which are synthesized from carbon dioxide and water -- hence the name photosynthesis , from the Greek φῶς , phōs , `` light '' , and σύνθεσις , synthesis , `` putting together '' . In most cases , oxygen is also released as a waste product . Most plants , most algae , and cyanobacteria perform photosynthesis ; such organisms are called photoautotrophs . Photosynthesis is largely responsible for producing and maintaining the oxygen content of the Earth 's atmosphere , and supplies all of the organic compounds and most of the energy necessary for life on Earth .   Although photosynthesis is performed differently by different species , the process always begins when energy from light is absorbed by proteins called reaction centres that contain green chlorophyll pigments . In plants , these proteins are held inside organelles called chloroplasts , which are most abundant in leaf cells , while in bacteria they are embedded in the plasma membrane . In these light-dependent reactions , some energy is used to strip electrons from suitable substances , such as water , producing oxygen gas . The hydrogen freed by the splitting of water is used in the creation of two further compounds that act as an immediate energy storage means : reduced nicotinamide adenine dinucleotide phosphate ( NADPH ) and adenosine triphosphate ( ATP ) , the `` energy currency '' of cells .   In plants , algae and cyanobacteria , long-term energy storage in the form of sugars is produced by a subsequent sequence of reactions called the Calvin cycle ; some bacteria use different mechanisms , such as the reverse Krebs cycle , to achieve the same end . In the Calvin cycle , atmospheric carbon dioxide is incorporated into already existing organic carbon compounds , such as ribulose bisphosphate ( RuBP ) . Using the ATP and NADPH produced by the light-dependent reactions , the resulting compounds are then reduced and removed to form further carbohydrates , such as glucose .   The first photosynthetic organisms probably evolved early in the evolutionary history of life and most likely used reducing agents such as hydrogen or hydrogen sulfide , rather than water , as sources of electrons . Cyanobacteria appeared later ; the excess oxygen they produced contributed directly to the oxygenation of the Earth , which rendered the evolution of complex life possible . Today , the average rate of energy capture by photosynthesis globally is approximately 130 terawatts , which is about three times the current power consumption of human civilization .  Photosynthetic organisms also convert around 100 -- 115 thousand million metric tonnes of carbon into biomass per year .

negative: Pumice Pumice ( -LSB- pronˈpʌmᵻs -RSB- ) , called pumicite in its powdered or dust form , is a volcanic rock that consists of highly vesicular rough textured volcanic glass , which may or may not contain crystals . It is typically light colored . Scoria is another vesicular volcanic rock that differs from pumice in having larger vesicles , thicker vesicle walls and being dark colored and denser .   Pumice is created when super-heated , highly pressurized rock is violently ejected from a volcano . The unusual foamy configuration of pumice happens because of simultaneous rapid cooling and rapid depressurization . The depressurization creates bubbles by lowering the solubility of gases ( including water and CO2 ) that are dissolved in the lava , causing the gases to rapidly exsolve ( like the bubbles of CO2 that appear when a carbonated drink is opened ) . The simultaneous cooling and depressurization freezes the bubbles in a matrix . Eruptions under water are rapidly cooled and the large volume of pumice created can be a shipping hazard for cargo ships .

negative: Carbon diet A carbon diet refers to reducing the impact on climate change by reducing greenhouse gas production specifically , CO2 production . In today 's society , we produce CO2 in every day activities such as driving , heating , deforestation and the burning of fossil fuels such as coal , oil and gas . It has been found that carbon dioxide from the burning of coal , natural gas , and oil for electricity and heat is the largest single source of global greenhouse gas emissions . For years , governments and corporations have been attempting to balance out their emissions by participating in carbon-offsetting -- the practice in which they invest in renewable energy to compensate for the global-warming pollution that they produce . Despite these efforts the results are still far off and we continue to see growth in CO2 concentration . Now , a growing number of individuals are trying to make a reduction in the amount of CO2 that is being produced by participating in low carbon dieting . This small adjustment in household CO2 production has the potential to reduce emissions much more quickly than other kinds of changes and it deserves explicit consideration as part of climate policy . It can potentially help avoid `` overshoot '' of greenhouse gas concentration targets ; provide a demonstration effect ; reduce emissions at low cost ; and buy time to develop new technologies , policies , and institutions to reach long-term greenhouse gas emission targets and to develop adaptation strategies .

negative: Hydrocarbon dew point The hydrocarbon dew point is the temperature ( at a given pressure ) at which the hydrocarbon components of any hydrocarbon-rich gas mixture , such as natural gas , will start to condense out of the gaseous phase . It is often also referred to as the HDP or the HCDP . The maximum temperature at which such condensation takes place is called the cricondentherm . The hydrocarbon dew point is a function of the gas composition as well as the pressure .   The hydrocarbon dew point is universally used in the natural gas industry as an important quality parameter , stipulated in contractual specifications and enforced throughout the natural gas supply chain , from producers through processing , transmission and distribution companies to final end users .   The hydrocarbon dew point of a gas is a different concept from the water dew point , the latter being the temperature ( at a given pressure ) at which water vapor present in a gas mixture will condense out of the gas .

negative: Air sensitivity Air sensitivity is a term used , particularly in chemistry , to denote the reactivity of chemical compounds with some constituent of air . Most often , reactions occur with atmospheric oxygen ( O2 ) or water vapor ( H2O ) , although reactions with the other constituents of air such as carbon monoxide ( CO ) , carbon dioxide ( CO2 ) , and nitrogen ( N2 ) are also possible .   The range of methods used to work with air-sensitive compounds are known as air-free techniques . Two main methods exist -- gloveboxes and Schlenk lines . Gloveboxes are sealed cabinets filled with an inert gas such as argon or nitrogen . Normal laboratory equipment can be set up and manipulated through the use of the gloves . A Schlenk line is a vacuum and inert-gas dual-manifold that allows glassware to be evacuated and refilled with inert gas .

negative: Wetland methane emissions As one of the most significant natural sources of atmospheric methane , wetlands remain a major area of concern with respect to climate change . Wetlands are characterized by water-logged soils and distinctive communities of plant and animal species that have evolved and adapted to the constant presence of water . Due to this high level of water saturation as well as warm weather , wetlands are one of the most significant natural sources of atmospheric methane .   Most methanogenesis , or methane production , occurs in oxygen-poor environments . Because the microbes that live in warm , moist environments consume oxygen more rapidly than it can diffuse in from the atmosphere , wetlands are the ideal anaerobic , or oxygen poor , environments for fermentation .   Fermentation is a process used by certain kinds of microorganisms to break down essential nutrients . In a process called acetoclastic methanogenesis , microorganisms from the classification domain archaea produce methane by fermenting acetate and H2-CO2 into methane and carbon dioxide .   H3C-COOH → CH4 + CO2   Depending on the wetland and type of archaea , hydrogenotrophic methanogenesis , another process that yields methane , can also occur . This process occurs as a result of archaea oxidizing hydrogen with carbon dioxide to yield methane and water .   4H2 + CO2 → CH4 + 2H2O

negative: Mars aircraft A Mars aircraft is a vehicle for flying in the atmosphere of Mars . So far , Mars lander entry , descent , and landing systems have passed through the atmosphere . Aircraft may provide in situ measurements of the atmosphere of Mars , as well as additional observations over extended areas . A long-term goal is to develop piloted Mars aircraft .   Compared to Earth , the air is thinner at the surface ( less than 1 % ) but the gravity is lower ( less than 40 % ) . Also , the major component of Mars air , CO2 gas , is denser than Earth air for a given pressure .

negative: Fossil fuel power station A fossil fuel power station is a power station which burns fossil fuel such as coal , natural gas , or petroleum to produce electricity . Central station fossil fuel power plants are designed on a large scale for continuous operation . In many countries , such plants provide most of the electrical energy used . Fossil fuel power stations have machinery to convert the heat energy of combustion into mechanical energy , which then operates an electrical generator . The prime mover may be a steam turbine , a gas turbine or , in small plants , a reciprocating internal combustion engine . All plants use the energy extracted from expanding gas , either steam or combustion gases . Very few MHD generators have been built which directly convert the energy of hot , moving water into electricity . MHD means Magnetohydrodynamics , which is the study of the magnetic properties of electrically conducting fluids . Examples of such magnetofluids include plasmas , liquid metals , salt water and electrolytes .   By-products of thermal power plant operation must be considered in their design and operation . Waste heat energy , which remains due to the finite efficiency of the Carnot , Rankine , or Diesel power cycle , is released directly to the atmosphere or river/lake water , or indirectly to the atmosphere using a cooling tower with river or lake water used as a cooling medium . The flue gas from combustion of the fossil fuels is discharged to the air . This gas contains carbon dioxide and water vapor , as well as other substances such as nitrogen oxides ( NOx ) , sulfur oxides ( SOx ) , mercury , traces of other metals , and , for coal-fired plants , fly ash . Solid waste ash from coal-fired boilers must also be removed . Some coal ash can be recycled for building materials .   Fossil fueled power stations are major emitters of carbon dioxide ( CO2 ) , a greenhouse gas which according to a consensus opinion of scientific organisations is a contributor to global warming . The results of a recent study show that the net income available to shareholders of large companies could see a significant reduction from the greenhouse gas emissions liability related to only natural disasters in the U.S. from a single coal-fired power plant . However , as of 2015 , no such cases have awarded damages in the U.S. Per unit of electric energy , brown coal emits nearly two times as much CO2 as natural gas , and black coal emits somewhat less than brown . Carbon capture and storage of emissions is not currently available .

negative: Molecular vapor deposition Molecular vapor deposition is the gas-phase reaction between surface reactive chemicals and an appropriately receptive surface . Often bi-functional silanes are used in which one termination of the molecule is reactive . For example , a functional chlorosilane ( R-Si-Cl3 ) can react with surface hydroxyl groups ( - OH ) resulting a radicalized ( R ) deposition on the surface . The advantage of a gas phase reaction over a comparable liquid phase process is the control of moisture from the ambient environment , which often results in cross polymerization of the silane leading to particulates on the treated surface . Often a heated sub-atmospheric vacuum chamber is used to allow precise control of the reactants and water content . Additionally the gas phase process allows for easy treatment of complex parts since the coverage of the reactant is generally diffusion limited . Microelectromechanical Systems ( MEMS ) sensors often use molecular vapor deposition as a technique to address stiction and other parasitic issues relative to surface-to-surface interactions .


query: While changes in cloud cover & aerosols lead to more sunlight hitting the surface, this can be compensated by the cooling effect on the atmosphere due to fewer clouds trapping less warmth and fewer absorbing aerosols absorbing less sunlight.

positive: Global dimming Global dimming is the gradual reduction in the amount of global direct irradiance at the Earth 's surface that was observed for several decades after the start of systematic measurements in the 1950s . The effect varies by location , but worldwide it has been estimated to be of the order of a 4 % reduction over the three decades from 1960 -- 1990 . However , after discounting an anomaly caused by the eruption of Mount Pinatubo in 1991 , a very slight reversal in the overall trend has been observed .   Global dimming is thought to have been caused by an increase in particulates such as sulfate aerosols in the atmosphere due to human action .   It has interfered with the hydrological cycle by reducing evaporation and may have reduced rainfall in some areas . Global dimming also creates a cooling effect that may have partially counteracted the effect of greenhouse gases on global warming .

positive: Particulates Atmospheric particulate matter -- also known as particulate matter ( PM ) or particulates -- are microscopic solid or liquid matter suspended in the Earth 's atmosphere . The term aerosol commonly refers to the particulate/air mixture , as opposed to the particulate matter alone . Sources of particulate matter can be man-made or natural . They have impacts on climate and precipitation that adversely affect human health .   Subtypes of atmospheric particulate matter include suspended particulate matter ( SPM ) , thoracic and respirable particles , inhalable coarse particles , which are -LSB- coarse -RSB- particles with a diameter between 2.5 and 10 micrometers ( μm ) ( PM10 ) , fine particles with a diameter of 2.5 μm or less ( PM2 .5 ) , ultrafine particles , and soot   The IARC and WHO designate airborne particulates a Group 1 carcinogen . Particulates are the deadliest form of air pollution due to their ability to penetrate deep into the lungs and blood streams unfiltered , causing permanent DNA mutations , heart attacks , and premature death . In 2013 , a study involving 312,944 people in nine European countries revealed that there was no safe level of particulates and that for every increase of 10 μg / m3 in PM10 , the lung cancer rate rose 22 % . The smaller PM2 .5 were particularly deadly , with a 36 % increase in lung cancer per 10 μg / m3 as it can penetrate deeper into the lungs .

positive: Climate system Earth's climate arises from the interaction of five major climate system components: the atmosphere (air), the hydrosphere (water), the cryosphere (ice and permafrost), the lithosphere (earth's upper rocky layer) and the biosphere (living things). Climate is the average weather, typically over a period of 30 years, and is determined by a combination of processes in the climate system, such as ocean currents and wind patterns. Circulation in the atmosphere and oceans is primarily driven by solar radiation and transports heat from the tropical regions to regions that receive less energy from the Sun. The water cycle also moves energy throughout the climate system. In addition, different chemical elements, necessary for life, are constantly recycled between the different components. The climate system can change due to internal variability and external forcings. These external forcings can be natural, such as variations in solar intensity and volcanic eruptions, or caused by humans. Accumulation of heat-trapping greenhouse gases, mainly being emitted by people burning fossil fuels, is causing global warming. Human activity also releases cooling aerosols, but their net effect is far less than that of greenhouse gases. Changes can be amplified by feedback processes in the different climate system components.

positive: Global warming Global warming , also referred to as climate change , is the observed century-scale rise in the average temperature of the Earth 's climate system and its related effects . Multiple lines of scientific evidence show that the climate system is warming . Many of the observed changes since the 1950s are unprecedented in the instrumental temperature record which extends back to the mid 19th century , and in paleoclimate proxy records over thousands of years .   In 2013 , the Intergovernmental Panel on Climate Change ( IPCC ) Fifth Assessment Report concluded that `` It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century . '' The largest human influence has been emission of greenhouse gases such as carbon dioxide , methane and nitrous oxide . Climate model projections summarized in the report indicated that during the 21st century the global surface temperature is likely to rise a further 0.3 to for their lowest emissions scenario and 2.6 to for the highest emissions scenario . These findings have been recognized by the national science academies of the major industrialized nations and are not disputed by any scientific body of national or international standing .   Future climate change and associated impacts will differ from region to region around the globe . Anticipated effects include warming global temperature , rising sea levels , changing precipitation , and expansion of deserts in the subtropics . Warming is expected to be greater over land than over the oceans and greatest in the Arctic , with the continuing retreat of glaciers , permafrost and sea ice . Other likely changes include more frequent extreme weather events including heat waves , droughts , heavy rainfall with floods and heavy snowfall ; ocean acidification ; and species extinctions due to shifting temperature regimes . Effects significant to humans include the threat to food security from decreasing crop yields and the abandonment of populated areas due to rising sea levels . Because the climate system has a large `` inertia '' and greenhouse gases will stay in the atmosphere for a long time , many of these effects will not only exist for decades or centuries , but will persist for tens of thousands of years .   Possible societal responses to global warming include mitigation by emissions reduction , adaptation to its effects , building systems resilient to its effects , and possible future climate engineering . Most countries are parties to the United Nations Framework Convention on Climate Change ( UNFCCC ) ,  whose ultimate objective is to prevent dangerous anthropogenic climate change . Parties to the UNFCCC have agreed that deep cuts in emissions are required and that global warming should be limited to well below 2.0 C-change relative to pre-industrial levels , with efforts made to limit warming to 1.5 C-change .   Public reactions to global warming and concern about its effects are also increasing . A global 2015 Pew Research Center report showed a median of 54 % consider it `` a very serious problem '' . There are significant regional differences , with Americans and Chinese ( whose economies are responsible for the greatest annual CO2 emissions ) among the least concerned .

negative: Plankton, Aerosol, Cloud, ocean Ecosystem Plankton , Aerosol , Cloud , ocean Ecosystem ( PACE ) is a NASA ocean color satellite mission that will continue and advance observations of ocean biology , biogeochemistry , and ecology , as well as aerosols and clouds . PACE data will be used to identify the extent and duration of harmful algal blooms and improve understanding of air quality . These and other uses of PACE data will benefit the economy and society , especially sectors that rely on water quality , fisheries and food security .   PACE will also measure atmospheric particles and clouds that scatter and absorb sunlight . Improved characterization of aerosol particles , in particular , will enable quantifying their impact on ocean biology and chemistry as well as Earth 's energy budget .   The PACE project is managed by NASA Goddard Space Flight Center . The main instrument and bus are being designed and built at NASA Goddard Space Flight Center . The satellite is planned for launch in 2022 .

negative: Sea salt aerosol Sea salt aerosol , which originally comes from sea spray , is one of the most widely distributed natural aerosols . Sea salt aerosols are characterized as non-light-absorbing , highly hygroscopic , and having coarse particle size . Some sea salt dominated aerosols could have a single scattering albedo as large as ~ 0.97 . Due to the hygroscopy , a sea salt particle can serve as a very efficient cloud condensation nuclei ( CCN ) , altering cloud reflectivity , lifetime , and precipitation process . According to the IPCC report , the total sea salt flux from ocean to atmosphere is ~ 3300 Tg/yr .

negative: Atmospheric Research Atmospheric Research is a scientific journal dealing with the part of the atmosphere where meteorological events occur ; intended for atmospheric scientists ( such as meteorologists and climatologists ) , aerosol scientists , and hydrologists . It is a highly international journal with attention given to all processes extending from the earth surface to the tropopause , but special emphasis continues to be devoted to the physics of clouds and precipitation , i.e. atmospheric aerosols ; microphysical processes ; cloud dynamics and thermodynamics ; numerical simulation of cloud processes ; clouds and radiation ; meso - and macrostructure of clouds and cloud systems , and weather modification .

negative: Robert Jay Charlson Robert Jay Charlson is an American atmospheric scientist , climate scientist , pioneer in the fields of climate forcing and climate change , and coauthor of the CLAW hypothesis . He is professor of Atmospheric Sciences , chemistry , and geophysics at the University of Washington in Seattle , Washington . Charlson earned his PhD from the University of Washington . He is a world expert in atmospheric chemistry , aerosol physics , aerosol/cloud/climate interaction , aerosol and cloud instrumentation .

negative: TanSat TanSat , also known as CarbonSat , is a Chinese Earth observation satellite dedicated to monitoring carbon dioxide in Earth 's atmosphere . It is generally classified as a minisatellite , and is the first dedicated carbon mission of the Chinese space program . The mission was formally proposed in 2010 , and work began in January 2011 . It is funded by the Ministry of Science and Technology ( MOST ) and was built by the Shanghai Institute of Microsystem And Information Technology ( SIMIT ) .   TanSat carries two instruments : the Carbon Dioxide Spectrometer and the Cloud and Aerosol Polarimetry Imager . The Carbon Dioxide Spectrometer ( CDS ) , also called CarbonSpec , is a high-resolution grating spectrometer which measures absorption at 1.61 µm and 2.06 µm , and absorption in reflected sunlight at 0.76 µm . The Cloud and Aerosol Polarimetry Imager ( CAPI ) is a wide-field , moderate-resolution , imaging spectrometer which works in concert with CDS by compensating for measurement errors caused by clouds and aerosols . It makes observations in ultraviolet ( 0.38 µm ) , visible ( 0.67 µm ) , and near infrared ( 0.87 µm , 1.375 µm , and 1.64 µm ) .

negative: Migration of marine species in the Northern Atlantic Ocean The world 's oceans are warming due to climate change . Climate change is caused by three major factors which are the greenhouse effect , variation in the sun 's energy that reaches Earth , and changes in reflectivity within Earth 's atmosphere and its surface . The greenhouse effect is caused by greenhouse gases that absorb sunlight . Energy from the sun that reaches Earth is either retained or sent into space . Greenhouse gases in Earth 's atmosphere such as carbon dioxide , methane , and water vapor absorb energy which cause a blanketing effect that warms the earth . Aerosols such as black carbon also catalyze the warming effect as they are unreflective and absorb energy from the sun supplementing greenhouse gases in the warming effect .   These combined factors are warming the Earth 's land as well as the oceans . Many fish species possess a certain range of water temperature that they are able to tolerate which is causing species to migrate to different areas where the water temperature is livable . The warming of the Atlantic Ocean is causing many fish species to shift north towards once cooler waters so they can live within their temperature range . Tropical species are being found outside their normal range and into more northern waters causing an array of ecological , economic , and fishery management problems .

negative: Stratospheric sulfur aerosols Stratospheric sulfur aerosols are sulfur-rich particles which exist in the stratosphere region of the Earth 's atmosphere . The layer of the atmosphere in which they exist is known as the Junge layer , or simply the stratospheric aerosol layer . These particles consist of a mixture of sulfuric acid and water . They are created naturally , such as by photochemical decomposition of sulfur-containing gases , e.g. carbonyl sulfide . When present in high levels , e.g. after a strong volcanic eruption such as Mount Pinatubo , they produce a cooling effect , by reflecting sunlight , and by modifying clouds as they fall out of the stratosphere . This cooling may persist for a few years before the particles fall out .   An aerosol is a suspension of fine solid particles or liquid droplets in a gas .  The sulfate particles or sulfuric acid droplets in the atmosphere are about 0.1 to 1.0 micrometer ( a millionth of a meter ) in diameter .   Sulfur aerosols are common in the troposphere as a result of pollution with sulfur dioxide from burning coal , and from natural processes . Volcanos are a major source of particles in the stratosphere as the force of the volcanic eruption propels sulfur-containing gases into the stratosphere . The relative influence of volcanoes on the Junge layer varies considerably according to the number and size of eruptions in any given time period , and also of quantities of sulfur compounds released . Only stratovolcanoes containing primarily granitic rocks are responsible for these fluxes , as basaltic rock erupted in shield volcanoes does n't result in plumes which reach the stratosphere .   Creating stratospheric sulfur aerosols deliberately is a proposed geoengineering technique which offers a possible solution to some of the problems caused by global warming . However , this will not be without side effects and it has been suggested that the cure may be worse than the disease .

negative: Stratospheric Aerosol and Gas Experiment The Stratospheric Aerosol and Gas Experiment ( SAGE ) is a series of remote sensing satellite instruments used to study the chemical composition of earth 's atmosphere . Specifically , SAGE has been used to study the Earth 's ozone layer and aerosols at the troposphere through the stratosphere . The SAGE instruments use solar occultation measurement technique to determine chemical concentrations in the atmosphere . Solar occultation measurement technique measures sunlight through the atmosphere and ratios that measurement with a sunlight measurement without atmospheric attenuation . This is achieved by observing sunrises and sunsets during a satellite orbit . Physically , the SAGE instruments measure ultraviolet/visible energy and this is converted via algorithms to determine chemical concentrations . SAGE data has been used to study the atmospheres aerosols , ozone , water vapor , and other trace gases .

negative: Closure (atmospheric science) A closure experiment in atmospheric science is a combination of different measurement techniques to describe the current state of the investigated system as fully as possible , and to find inaccuracies in one or some of the methods involved . The comparison of different types of measurement often involves model calculations , which may also be tested in this process .   A common example for closure experiments are aerosol studies . Aerosols can be studied from space , from aircraft , and from the surface . The different properties of aerosols ( chemical composition , particle size , particle number concentration , optical absorptivity , thermal emissivity , index of refraction , pattern of light scattering , etc. ) require very different kinds of measurement techniques . Different instruments have been developed to perform each technique , and researchers usually specialize in one or a few of them . Due to the logistic efforts required to bring different groups of researchers with different measurement techniques together , such experiments stand out among routine experiments that are more focused on one or a few techniques and have fewer participants .   An aerosol closure experiment might look like this :  Individual aerosol particles are sampled , and their size and shape are determined under an electron microscope ;  A lidar emits a laser beam into the aerosol plume and detects the backscatter signal ;  An aerosol flow is led through optical detectors that record the size distribution of the particles ;  The sunlight attenuated by the aerosol is measured by a sun photometer , yielding the optical depth of the aerosol layer ;  the spectral absorption of sunlight , as well as the scattering properties of the aerosol are measured by spectrometers ;  The extent and total reflectivity of the aerosol plume are observed by a satellite radiometer .   Additionally , measurements can be performed within the plume or outside , by means of remote sensing , from the surface , from aircraft , and from satellites in space . Different viewing geometries again introduce complexity , which can be assessed in closure experiments .   Algorithms exist , for example , to predict the optical properties from a given particle shape , size distribution , and index of refraction . Closure is achieved if the predictions of such an algorithm agree ( within the limits of measurement uncertainty ) with the optical properties that have been derived from the independent radiation measurements ; if the lidar information about the vertical distribution of the aerosol sums up to the total optical depth determined by the sun photometer ; etc. .

negative: Ceilometer A ceilometer is a device that uses a laser or other light source to determine the height of a cloud base . Ceilometers can also be used to measure the aerosol concentration within the atmosphere .

negative: Peter V. Hobbs Peter Victor Hobbs ( 1936 -- 2005 ) was a British-born professor of Atmospheric Sciences and Director of the Cloud and Aerosol Research Group at the University of Washington . His research interests were in the physics and chemistry of the atmosphere , focusing on the roles played by aerosols , clouds , and precipitation . He authored over 250 peer-reviewed papers , authored four books , and edited three books . He is the coauthor with John Michael Wallace of what is generally considered the standard introductory textbook in the field : Atmospheric Science : An Introductory Survey .

negative: CLOUD experiment Cosmics Leaving Outdoor Droplets or CLOUD is an experiment being run at CERN by a group of researchers led by Jasper Kirkby to investigate the microphysics between galactic cosmic rays ( GCRs ) and aerosols under controlled conditions . The experiment began operation in November 2009 .   The primary goal is to understand the influence of galactic cosmic rays ( GCRs ) on aerosols and clouds , and their implications for climate . Although its design is optimised to address the cosmic ray question , ( as posed by Henrik Svensmark and colleagues in 1997 ) CLOUD allows as well to measure aerosol nucleation and growth under controlled laboratory conditions . Atmospheric aerosols and their effect on clouds are recognised by the IPCC as main source of uncertainty in present radiative forcing and climate models .

negative: Sulfate aerosol The term sulfate aerosols is used for a suspension of fine solid particles of a sulfate or tiny droplets of a solution of a sulfate or of sulfuric acid ( which is not technically a sulfate ) . They are produced by chemical reactions in the atmosphere from gaseous precursors ( with the exception of sea salt sulfate and gypsum dust particles ) . The two main sulfuric acid precursors are sulfur dioxide ( SO2 ) from anthropogenic sources and volcanoes , and dimethyl sulfide ( DMS ) from biogenic sources , especially marine plankton . These aerosols can cause a cooling effect on earth .   However the UNFCCC has noted that sulfate aerosols remain in the atmosphere for only a short amount of time in comparison to other greenhouse gases , and therefore their cooling is localized and temporary . Other side effects of sulfate aerosols in the environment include poor air quality .

negative: Angstrom exponent Ångström exponent is the name of the exponent in the formula that is usually used to describe the dependency of the aerosol optical thickness , or aerosol extinction coefficient on wavelength .   Depending on particle size distribution , the spectral dependence of the aerosol optical thickness is given approximately by   where is the optical thickness at wavelength , and is the optical thickness at the reference wavelength . In principle , if the optical thickness at one wavelength and the Ångström exponent are known , the optical thickness can be computed at a different wavelength . In practice , measurements are made of the optical thickness of an aerosol layer at two different wavelengths , and the Ångström exponent is estimated from these measurements using this formula . The aerosol optical thickness can then be derived at all other wavelengths , within the range of validity of this formula .   For measurements of optical thickness and taken at two different wavelengths and respectively , the Ångström exponent is given by   The Ångström exponent is inversely related to the average size of the particles in the aerosol : the smaller the particles , the larger the exponent . Thus , Ångström exponent is a useful quantity to assess the particle size of atmospheric aerosols or clouds , and the wavelength dependence of the aerosol/cloud optical properties . For example , cloud droplet , usually with large sizes and thus very smaller Ångström exponent ( nearly zero ) , is spectrally neutral , which means , e.g. , the optical depth does not change with wavelength . This exponent is now routinely estimated by analyzing radiation measurements acquired on Earth Observation platforms , such as AErosol RObotic NETwork , or AERONET .

negative: Noctilucent cloud Night clouds or noctilucent clouds are tenuous cloud-like phenomena in the upper atmosphere . They are visible in a deep twilight . They are made of ice crystals . Noctilucent roughly means night shining in Latin . They are most commonly observed in the summer months at latitudes between 50 ° and 70 ° north and south of the equator . These clouds can be observed only during local summer months and when the Sun is below the horizon for the observer , but while the clouds are still in sunlight .   They are the highest clouds in Earth 's atmosphere , located in the mesosphere at altitudes of around 76 to . They are too faint to be seen during daylight , and are visible only when illuminated by sunlight from below the horizon while the lower layers of the atmosphere are in the Earth 's shadow . Noctilucent clouds are not fully understood and are a recently discovered meteorological phenomenon ; there is no confirmed record of their observation before 1885 , although they may have been observed a few decades earlier by Thomas Romney Robinson in Armagh . Doubts now surround Robinson 's out-of-season records , following observations , from several points around high northern latitudes , of NLC-like phenomena following the Chelyabinsk bolide entry in February 2013 ( outside the NLC season ) that were in fact stratospheric dust reflections visible after sunset .   Noctilucent clouds can form only under very restricted conditions during local summer ; their occurrence can be used as a sensitive guide to changes in the upper atmosphere . They are a relatively recent classification . The occurrence of noctilucent clouds appears to be increasing in frequency , brightness and extent .

negative: Cloud Aerosol Transport System The Cloud Aerosol Transport System ( CATS ) is a light detection and ranging remote sensing instrument designed to measure the location , composition and distribution of pollution , dust , smoke , aerosols and other particulates in the atmosphere . CATS is to be installed on the Kibo module of the International Space Station and is expected to run for at least six months , and up to three years .   It was launched in January 2015 aboard the SpaceX CRS-5 resupply mission . CATS will use a laser operating at three wavelengths ( 1064 , 532 , and 355 nm ) to determine cloud layer height , thickness , and depth . Some of the applications of the data gathered will be to develop and refine climate models as well as providing insight for future examinations of the atmospheres of Mars , Jupiter , and other extraterrestrial atmospheres .

negative: Earth's energy budget Earth 's energy budget accounts for the energy Earth receives from the Sun . Much of this energy is lost when the earth re-radiates it back into outer space , and the rest of the energy is distributed throughout the five components of Earth 's climate system . This system is made up of earth 's water , ice , atmosphere , rocky crust , and all living things .   Quantifying changes in these amounts is required to accurately model the Earth 's climate .   Received radiation is unevenly distributed over the planet , because the Sun heats equatorial regions more than polar regions . Energy is absorbed by the atmosphere , hydrosphere , and lithosphere , and , in a process informally described as Earth 's heat engine , the solar heating is redistributed through evaporation of surface water , convection , rainfall , winds , and ocean circulation . When the incoming solar energy is balanced by an equal flow of heat to space , the Earth is said to be in radiative equilibrium and under that condition , global temperatures will be stable .   Disturbances of Earth 's radiative equilibrium , such as an increase of greenhouse gases , will change global temperatures in response . However , Earth 's energy balance and heat fluxes depend on many factors , such as atmospheric composition ( mainly aerosols and greenhouse gases ) , the albedo ( reflectivity ) of surface properties , cloud cover and vegetation and land use patterns . Changes in surface temperature due to Earth 's energy budget do not occur instantaneously , due to the inertia of the oceans and the cryosphere . The net heat flux is buffered primarily by becoming part of the ocean 's heat content , until a new equilibrium state is established between radiative forcings and the climate response .

negative: Manipulation of atoms by optical field When a group of atoms is super-cooled to temperatures near absolute zero , they form a Bose -- Einstein condensate , a state of matter where quantum effects can be observed in the macroscopic system . In this state , the trajectories of the atoms can be manipulated using light .   If a super-cooled atomic gas is placed in a standing light wave produced by two counter-propagating lasers of certain frequency , the atoms are diffracted in different order . A cold atom absorbs a photon from one of the laser beams and emits a photon in the other beam receiving a net momentum of in the direction of the absorbed photon . Here is the magnitude of the wave vector of the laser . This is called two-photon recoil process . In such situation , a BEC cloud sitting at the center of a trap is split into two identical clouds . The clouds then travel in opposite directions with a velocity , in the direction of the photon .

negative: Black carbon Chemically , black carbon ( BC ) is a component of fine particulate matter ( PM ≤ 2.5 µm in aerodynamic diameter ) . Black carbon consists of pure carbon in several linked forms . It is formed through the incomplete combustion of fossil fuels , biofuel , and biomass , and is emitted in both anthropogenic and naturally occurring soot .   Black carbon causes human morbidity and premature mortality .   In climatology , black carbon is a climate forcing agent . Black carbon warms the Earth by absorbing sunlight and heating the atmosphere and by reducing albedo when deposited on snow and ice ( direct effects ) and indirectly by interaction with clouds , with the total forcing of 1.1 W/m2 . Black carbon stays in the atmosphere for only several days to weeks , whereas carbon dioxide has an atmospheric lifetime of more than 100 years .   The term black carbon is also used in soil sciences and geology , referring either to deposited atmospheric black carbon or to directly incorporated black carbon from vegetation fires . Especially in the tropics , black carbon in soils significantly contributes to fertility as it is able to absorb important plant nutrients .

negative: Volcanic impacts on the oceans Explosive volcanic eruptions affect the global climate mainly through injecting sulfur bearing gases into the stratosphere , which oxidize to form sulfate aerosols . Stratospheric sulfur aerosols spread around the globe by the atmospheric circulation , producing surface cooling by scattering solar radiation back to space . This cooling effect on the ocean surface usually lasts for several years as the lifetime of sulfate aerosols is about 2 -- 3 years . However , in the subsurface ocean the cooling signal may persist for a longer time and may have impacts on some decadal variabilities , such as the Atlantic meridional overturning circulation ( AMOC ) .

negative: Atmospheric lidar Atmospheric lidar is a class of instruments that uses laser light to study atmospheric properties from the ground up to the top of the atmosphere . Such instruments have been used to study , among other , atmospheric gases , aerosols , clouds , and temperature .

negative: Aerosol burn An aerosol burn is an injury to the skin caused by the pressurized gas within an aerosol spray cooling quickly , with the sudden drop in temperature sufficient to cause frostbite to the applied area . Medical studies have noted an increase of this practice , known as `` frosting '' , in pediatric and teenage patients .   Adiabatic expansion causes the gas ( with a low boiling temperature ) to rapidly cool on exit from the aerosol applier . According to controlled laboratory experiments , the gas from a typical deodorant spray can reduce skin temperature by up to sixty degrees Celsius .   The form of injury is freezing of the skin , a type of frostbite . It is highly advised for those who suffer from frostbite to seek medical attention .   In rare cases aerosol-induced burns can be severe enough to necessitate skin grafting .

negative: Belt of Venus The Belt of Venus or Venus 's Girdle or Twilight Wedge is an atmospheric phenomenon seen shortly before sunrise or shortly after sunset . The observer is , or is very nearly , surrounded by a pinkish glow ( or anti-twilight arch ) that extends roughly 10 ° -- 20 ° above the horizon .   Like alpenglow , backscattering of reddened sunlight also creates the Belt of Venus . Unlike the Belt of Venus , the direct illumination of clouds and aerosols that create the afterglow which characterizes alpenglow hover low in the atmosphere and create a red horizontal band visible just after sunset or before sunrise . Unlike alpenglow , the sunlight refracted in the fine dust particles that create the rosy pinkish arch of the Belt of Venus hover high in the atmosphere and perpetuate it long after sunset or long before sunrise . In a way , the Belt of Venus is a true alpenglow visible at twilight near the anti-solar point .   Often , the glow is separated from the horizon by a dark layer , the Earth 's shadow or `` dark segment . '' The arch 's light pink color is due to backscattering of reddened light from the rising or setting Sun . A very similar effect can be seen during a total solar eclipse . The zodiacal light , which is caused by reflection of sunlight from the interplanetary dust in the solar system , is also a similar phenomenon .   The name of the phenomenon alludes to the cestus , a girdle or breast-band , of the Ancient Greek goddess Aphrodite , customarily equated with the Roman goddess Venus .

negative: Extraterrestrial atmosphere The study of extraterrestrial atmospheres is an active field of research , both as an aspect of astronomy and to gain insight into Earth 's atmosphere . In addition to Earth , many of the other astronomical objects in the Solar System have atmospheres . These include all the gas giants , as well as Mars , Venus , and Pluto . Several moons and other bodies also have atmospheres , as do comets and the Sun . There is evidence that extrasolar planets can have an atmosphere . Comparisons of these atmospheres to one another and to Earth 's atmosphere broaden our basic understanding of atmospheric processes such as the greenhouse effect , aerosol and cloud physics , and atmospheric chemistry and dynamics .

negative: False sunset A false sunset can refer to one of two related atmospheric optical phenomena , where either 1 ) the sun appears to be setting below the horizon , while in reality it is still some distance above it , or 2 ) the sun has already set , but still appears to be on or above the horizon ( thus representing the reverse of a false sunrise ) . Depending on circumstances , these phenomena can give the impression of an actual sunset .   There are several atmospheric conditions which may cause the effect , most commonly a type of halo , caused by the  reflection and refraction of sunlight by small ice crystals in the atmosphere , often in the form of cirrus or cirrostratus clouds . Depending on which variety of `` false sunset '' is meant , the halo has to appear either above the sun ( which itself is hidden below the horizon ) or below it ( in which case the real sun is obstructed from view , e.g. by clouds or other objects ) , making the upper and lower tangent arc , upper and lower sun pillars and the subsun the most likely candidates .   Similarly to a false sunrise , other atmospheric circumstances may be responsible for the effect as well , such as simple reflection of the sunlight off the bottom of the clouds , or a type of mirage like the Novaya Zemlya effect .

negative: AERONET AERONET - the AERONET ( AErosol RObotic NETwork ) is a network of ground-based sun photometers which measure atmospheric aerosol properties . The measurement system is a solar-powered CIMEL Electronique 318A spectral radiometer that measures Sun and sky radiances at  a number of fixed wavelengths within the visible and near-infrared spectrum . There is one sea-based reading location aboard the E/V Nautilus , the exploration vessel operated by Dr. Robert Ballard and the Sea Research Foundation . Two readings per day are taken aboard the ship while it is in operation .   AERONET provides continuous cloud-screened observations of spectral aerosol optical depth ( AOD ) , precipitable water , and inversion aerosol products in diverse aerosol  regimes . Inversion products are retrieved from almucantar scans of radiance as a function of scattering angle and include products such as aerosol volume size distribution , aerosol complex refractive index , optical absorption ( single scattering albedo ) and the aerosol scattering phase function . All these products represent an average of the total aerosol column within the atmosphere .   The aerosol properties are retrieved via an inversion algorithm developed by Dubovik and King ( 2000 ) .  Further algorithms were developed , for example , by Dubovik et al. ( 2006 ) to take into account non-spherical shapes of aerosol particles such as mineral dust .   AERONET is an observing system in the NOAA Observing System Architecture .

negative: Subsidence (atmosphere) Subsidence in the Earth 's atmosphere is most commonly caused by low temperatures : as air cools , it becomes denser and moves towards the ground , just as warm air becomes less dense and moves upwards . Cool subsiding air is subject to adiabatic warming which tends to cause the evaporation of any clouds that might be present . Subsidence generally causes high barometric pressure as more air moves into the same space : the polar highs are areas of almost constant subsidence , as are the horse latitudes , and these areas of subsidence are the sources of much of the world 's prevailing wind . Subsidence also causes many smaller-scale weather phenomena , such as morning fog . An extreme form of subsidence is a downburst , which can result in damage similar to that produced by a tornado . A milder form of subsidence is referred to as downdraft .   Category : Atmosphere  Category : Basic meteorological concepts and phenomena

negative: Jasper Kirkby Jasper Kirkby is a British experimental particle physicist currently with CERN . He originated the idea for the Tau-Charm Factory , an accelerator now under construction as BEPC II in Beijing . He has led several large particle accelerator experiments at SPEAR ; the Paul Scherrer Institute ; and most recently , the CLOUD experiment at CERN .   The CLOUD experiment is investigating possible physical mechanisms for solar/cosmic ray forcing - a theory whereby cloud nucleation is affected by cosmic rays and the cosmic rays are affected by solar activity . The main purpose of the CLOUD experiment is to simulate the conditions under which clouds form in earth 's atmosphere -- specifically , the process by which cloud condensation nuclei form from aerosols in the atmosphere . Kirkby et al. published the results of CLOUD 's first experiment in the journal Nature in 2011 , reporting that cosmic rays `` seemed to enhance the production of nanometre-sized particles from the gaseous atmosphere by more than a factor of ten . '' He added , however , that the particles in question are far too small to serve as cloud condensation nuclei , adding , `` At the moment , it actually says nothing about a possible cosmic-ray effect on clouds and climate , but it 's a very important first step . ''

negative: Crown flash Crown flash is a rare but observed phenomenon involving `` The brightening of a thunderhead crown followed by the appearance of aurora-like streamers emanating into the clear atmosphere '' . The current hypothesis is that sunlight is reflecting off or refracting through tiny ice crystals above the crown of a cumulonimbus cloud . These ice crystals are aligned by the strong electro-magnetic effects around the cloud , so the effect may appear as a tall streamer or pillar of light . When the electro-magnetic field is disturbed by lightning flashes within the cloud , the ice crystals are re-orientated causing the light pattern to shift very rapidly and appear to ` dance ' in a strikingly mechanical fashion . The effect may also sometimes known as a `` leaping sundog '' . As with sundogs , the observer would have to be in a specific position to see the effect , which is not a self-generated light such as seen in a lightning strike , but rather a changing reflection/refraction of the sunlight .   Mentioned in Nature in 1971 and in a letter to Nature slightly earlier in the same year , this phenomenon is regarded as rare and not well documented . Recently several YouTube videos have emerged that appear to document this phenomenon .

negative: Cloud physics Cloud physics is the study of the physical processes that lead to the formation , growth and precipitation of atmospheric clouds . These aerosols are found in the troposphere , stratosphere , and mesosphere , which collectively make up the greatest part of the homosphere . Clouds consist of microscopic droplets of liquid water ( warm clouds ) , tiny crystals of ice ( cold clouds ) , or both ( mixed phase clouds ) . Cloud droplets initially form by the condensation of water vapor onto condensation nuclei when the supersaturation of air exceeds a critical value according to Köhler theory . Cloud condensation nuclei are necessary for cloud droplets formation because of the Kelvin effect , which describes the change in saturation vapor pressure due to a curved surface . At small radii , the amount of supersaturation needed for condensation to occur is so large , that it does not happen naturally . Raoult 's Law describes how the vapor pressure is dependent on the amount of solute in a solution . At high concentrations , when the cloud droplets are small , the supersaturation required is smaller than without the presence of a nucleus .   In warm clouds , larger cloud droplets fall at a higher terminal velocity ; because at a given velocity , the drag force per unit of droplet weight on smaller droplets is larger than on large droplets . The large droplets can then collide with small droplets and combine to form even larger drops . When the drops become large enough that their downward velocity ( relative to the surrounding air ) is greater than the upward velocity ( relative to the earth ) of the surrounding air , the drops can fall to the earth as precipitation . The collision and coalescence is not as important in mixed phase clouds where the Bergeron process dominates . Other important processes that form precipitation are riming , when a supercooled liquid drop collides with a solid snowflake , and aggregation , when two solid snowflakes collide and combine . The precise mechanics of how a cloud forms and grows is not completely understood , but scientists have developed theories explaining the structure of clouds by studying the microphysics of individual droplets . Advances in weather radar and satellite technology have also allowed the precise study of clouds on a large scale .

negative: Capping inversion A capping inversion is an elevated inversion layer that caps a convective boundary layer .   The boundary layer is the part of the atmosphere which is closest to the ground . Normally , the sun heats the ground , which in turn heats the air just above it . Thermals form when this warm air rises into the cold air ( warm air is less dense than cold air ) , a process described by convection . A convective layer such as this has the potential for cloud formation , since condensation occurs as the warm air rises and cools .   An inversion occurs when the normal temperature ( warm air below , cold air above ) profile is reversed , creating a stable configuration of dense , cold air sitting below lighter , warm air . An elevated inversion layer is thus a region of warm air above a region of cold air , but higher in the atmosphere ( generally not touching the surface ) .   A capping inversion occurs when there is a boundary layer with a normal temperature profile ( warm air rising into cooler air ) and the layer above that is an inversion layer ( cooler air below warm air ) . Cloud formation from the lower layer is `` capped '' by the inversion layer . If the capping inversion layer or `` cap '' is too strong ( too close to the surface ) , it will prevent thunderstorms from developing . A strong cap can result in foggy conditions .   However , if the air at the surface is unstable enough , strong updrafts can be forced through the capping inversion . This selective process of only allowing the strongest updrafts to form thunderstorms often results in outbreaks of severe weather .

negative: Morning Glory cloud The Morning Glory cloud is a rare meteorological phenomenon consisting of a low-level atmospheric solitary wave and associated cloud , occasionally observed in different locations around the world . The wave often occurs as an amplitude-ordered series of waves forming bands of roll clouds .   The southern part of the Gulf of Carpentaria in Northern Australia is the only known location where it can be predicted and observed on a more or less regular basis due to the configuration of land and sea in the area .