Water Vapor and Climate

<?xml version="1.0" encoding="UTF-8"?>  <XholonWorkbook> <Notes><![CDATA[ Xholon ------ Title: Water Vapor and Climate Description: Url: http://www.primordion.com/Xholon/wb/ InternalName: YoutubeId: Keywords: My Notes -------- How to Run the app that's contained within this workbook :: Click the Run button above. Look at the list of atmospheric molecules, some of which are greenhouse gases. That's all it does for now (TODO). The Heartland Institute is 'an American conservative and libertarian public policy think tank based in Chicago ... described by the New York Times as "the primary American organization pushing climate change skepticism".' (source: Wikipedia). :: http://heartland.org/ http://en.wikipedia.org/wiki/Heartland_Institute The Heartland Institute runs a website called climatewiki :: http://www.climatewiki.org/index.php/Main_Page The Science category in the climatewiki includes an article on greenhouse gases which I found interesting :: http://www.climatewiki.org/index.php/Greenhouse_Gas The content of the page seems generally factual, yet near the top of the article is a large graphic and supporting text, with the message :: "WATER VAPOR IS EARTH'S PREDOMINANT GREENHOUSE GAS. MAN-MADE CARBON DIOXIDE HAS NEGLIGABLE IMPACT ON EARTH'S TEMPERATURE. ... REDUCING MAN MADE CO2 WILL HAVE NO MEASURABLE EFFECT ON EARTH'S TEMPERATURE READINGS." "DATA SOURCE: http://www.geocraft.com/WVFossils/greenhouse_data.html" "Reducing our so-called “Carbon Footprint” by encouraging renewable energy and restricting fossil fuel development makes no sense when the actual composition of the greenhouse is considered. This 1 page graphic shows that water vapor is the overwhelming predominant component of our vital protective greenhouse envelope. Far from being detrimental, greenhouse gases retain the sun’s radiant heat and keep planet Earth from becoming frozen and uninhabitable. Despite the science that contradicts them, the so-called “warmists” contend that man’s CO2 emissions are somehow harmful to our existence. This pictorial representation of the greenhouse envelope clearly demonstrates that man-made CO2 emissions are relatively so tiny that they are of negligible impact and must be viewed accordingly." I know little about the role of water vapor in climate change. I'll do some research and report my findings here. Various points from climatewiki and Wikipedia articles, with my comments :: "A greenhouse gas (sometimes abbreviated 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." [1] "A greenhouse gas (sometimes abbreviated 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." [2] Both sites agree on the definition of greenhouse gas. The "thermal infrared range" is heat. :: "The primary greenhouse gases in the Earth's atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone." [1] "The primary greenhouse gases in the Earth's atmosphere are water vapour, carbon dioxide, methane, nitrous oxide, and ozone." [3] Everyone agrees on this. :: "Greenhouse gases greatly affect the temperature of the Earth; without them, Earth's surface would be on average about 33 °C (59 °F) colder than at present." [1] "Greenhouse gases greatly affect the temperature of the Earth; without them, Earth's surface would be on average about 33 °C (59 °F) colder than at present." [2] This is the greenhouse effect. On a cold sunny day it will be warmer in a glass- or plastic-enclosed greenhouse than outside (without a greenhouse). The same is true of the atmosphere - it's warmer with greenhouse gases. :: "The contribution to the greenhouse effect by a gas is affected by both the characteristics of the gas and its abundance. For example, on a molecule-for-molecule basis methane is about eighty times stronger greenhouse gas than carbon dioxide, but it is present in much smaller concentrations so that its total contribution is smaller." [1] "The contribution of each gas to the greenhouse effect is affected by the characteristics of that gas, its abundance, and any indirect effects it may cause. For example, on a molecule-for-molecule basis the direct radiative effects of methane is about 72 times stronger than carbon dioxide over a 20 year time frame but it is present in much smaller concentrations so that its total direct radiative effect is smaller, and it has a shorter atmospheric lifetime." [2] I'm not sure yet what the indirect effects are. The graphic at the top of the climatewiki page only mentions the abundance of different greenhouse gases, but ignores the characteristics of these gases, and their indirect effects. :: "Aside from water vapor, which has a residence time of about nine days, major greenhouse gases are well-mixed, and take many years to leave the atmosphere." [1] "Aside from water vapor, which has a residence time of about nine days, major greenhouse gases are well-mixed, and take many years to leave the atmosphere." [2] Residence time is one of the key characteristics of a gas, that must be considered in addition to the abundance. :: "When these gases are ranked by their direct contribution to the greenhouse effect, the most important are:" [2] |Gas Formula Contribution(%) -------------- ------- --------------- Water vapor H2O 36 – 72 % Carbon dioxide CO2 9 – 26 % Methane CH4 4 – 9 % Ozone O3 3 – 7 %| Water vapor makes a much greater contribution (about 4 times more; 36% vs 9%) to the greenhouse effect than does Carbon Dioxide. The graphic at the top of the climatewiki page represents the effect of different greenhouse gases using water droplets and dots. 9500 droplets (95%) represent the water vapor, while 348 dots (3.48%) represent the carbon dioxide. By this reckoning, the proportion is 95% vs 3.48% . There's a huge difference in the results obtained from these two ways of calculating. The climatewiki page does not include this data about the "direct contribution to the greenhouse effect". :: "The global warming potential (GWP) depends on both the efficiency of the molecule as a greenhouse gas and its atmospheric lifetime. GWP is measured relative to the same mass of CO2 and evaluated for a specific timescale." [1] "The global warming potential (GWP) depends on both the efficiency of the molecule as a greenhouse gas and its atmospheric lifetime. GWP is measured relative to the same mass of CO2 and evaluated for a specific timescale." [2] :: "Examples of the atmospheric lifetime and GWP relative to CO2 for several greenhouse gases are given in the following table:" [2] |Atmospheric lifetime and GWP relative to CO2 at different time horizon for various greenhouse gases. Gas name Chemical Lifetime Global warming potential (GWP) for given time horizon formula (years) 20-yr 100-yr 500-yr -------------------- -------- -------- ------- -------- ------------------------------------ Carbon dioxide CO2 30–95 years 1 1 1 Methane CH4 12 72 25 7.6 Nitrous oxide N2O 114 289 298 153 CFC-12 CCl2F2 100 11000 10900 5200 HCFC-22 CHClF2 12 5160 1810 549 Tetrafluoromethane CF4 50000 5210 7390 11200 Hexafluoroethane C2F6 10000 8630 12200 18200 Sulphur hexafluoride SF6 3200 16300 22800 32600 Nitrogen trifluoride NF3 740 12300 17200 20700 | The climatewiki page does not include this table. The Wikipedia page does not include Water Vapor in this table. I think that the main reason why Water Vapor is not in the table has to do with the fact that it has a "residence time of about nine days", instead of the multi-year residence times of Carbon Dioxide and other greenhouse gases. So each molecule of anthropogenic (man-made) Carbon Dioxide stays in the atmosphere for 30–95 (average 62.5) |years|, while each molecule of anthropogenic Water Vapor only stays for an average of 9 |days| before it precipitates out as rain or snow. 62.5 years = 62.5 * 365 = 22812 days. 22812 / 9 = 2535. So while total Water Vapor is the dominant contributor to the naturally-occuring greenhouse effect, anthropogenic Water Vapor has almost no direct effect. It just washes away. I'll try to confirm this. :: "Water vapor accounts for the largest percentage of the greenhouse effect, between 36% and 66% for clear sky conditions and between 66% and 85% when including clouds. Water vapor concentrations fluctuate regionally, but human activity does not significantly affect water vapor concentrations except at local scales, such as near irrigated fields. The atmospheric concentration of vapor is highly variable, from less than 0.01% in extremely cold regions up to 20% in warm, humid regions. ... The average residence time of a water molecule in the atmosphere is only about nine days, compared to years or centuries for other greenhouse gases such as CH4 and CO2." [2] These sentences are missing from the climatewiki page. :: "water vapor responds to and amplifies effects of the other greenhouse gases. The Clausius-Clapeyron relation establishes that air can hold more water vapor per unit volume when it warms. This and other basic principles indicate that warming associated with increased concentrations of the other greenhouse gases also will increase the concentration of water vapor. Because water vapor is a greenhouse gas, this results in further warming and so is a "positive feedback" that amplifies the original warming." [2] This information is missing from the climatewiki page. :: "While water vapour is indeed the most important greenhouse gas, the issue that makes it a feedback (rather than a forcing) is the relatively short residence time for water in the atmosphere (around 10 days)." [7] References :: 1. permalink (May 22, 2012) http://www.climatewiki.org/index.php?title=Greenhouse_Gas&oldid=2524 2. permalink (May 23, 2012) http://en.wikipedia.org/w/index.php?title=Greenhouse_gas&oldid=493645773 3. permalink (May 22, 2012) http://en.wikipedia.org/w/index.php?title=Atmosphere_of_Earth&oldid=489897718 4. permalink (May 23, 2012) http://en.wikipedia.org/w/index.php?title=Greenhouse_effect&oldid=493539111 5. permalink (May 23, 2012) http://en.wikipedia.org/w/index.php?title=Global-warming_potential&oldid=493056906 6. http://www.geocraft.com/WVFossils/greenhouse_data.html 7. http://www.realclimate.org/index.php/archives/2005/04/water-vapour-feedback-or-forcing/ 8. http://www.skepticalscience.com/Evaporating-the-water-vapor-argument.html ]]></Notes> <script implName="lang:python:inline:"><![CDATA[ print "" ]]></script> <script implName="lang:javascript:inline:"><![CDATA[ print("\n"); ]]></script> <_-.XholonClass>  <PhysicalSystem/> <AtmosphericMolecule>   <Nitrogen/> <Oxygen/> <Argon/> <CarbonDioxide/>  <Neon/> <Helium/> <Methane/>  <Krypton/> <Hydrogen/> <NitrousOxide/>  <CarbonMonoxide/> <Xenon/> <Ozone/>  <NitrogenDioxide/> <Iodine/> <Ammonia/>  <WaterVapor/>  </AtmosphericMolecule>  <AtmosphericMolecules/> </_-.XholonClass> <xholonClassDetails> </xholonClassDetails> <PhysicalSystem> <AtmosphericMolecules>  <Nitrogen>780840.0</Nitrogen>  <Oxygen>209460.0</Oxygen>  <Argon>9340.0</Argon>  <CarbonDioxide>394.45</CarbonDioxide>  <Neon>18.18</Neon>  <Helium>5.24</Helium>  <Methane>1.79</Methane>    <WaterVapor>4000</WaterVapor>  </AtmosphericMolecules> </PhysicalSystem> <Blockbehavior implName="lang:python:inline:"><![CDATA[ ]]></Blockbehavior> <Blockbehavior implName="lang:javascript:inline:"><![CDATA[ ]]></Blockbehavior> <Blockbehavior implName="lang:webEditionjs:inline:"><![CDATA[ this.bindPorts(this.parent()); this.height.incVal(0.02); print("JavaScript wants something to do. 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