The science and economics of Climate Change2007

The science and economics of Climate Change2007 - The...

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1 The science and economics of Climate Change September 2007
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2 Topics The science of greenhouse gasses. Modeling climate change The economics of climate change
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3 The gasses Major greenhouse gasses Methane, Nitrous Oxide, Carbon Dioxide. The global warming potential, per molecule, of Methane 2 is 25 times greater than a molecule of CO2, and global warming potential of a molecule Nitrous Oxide is 200 greater than a molecule of CO2. (Reducing meat consumption and shifting ag production from animal feed to biofuel stock who reduce methane – from animals – and also reduce C02 emissions.) CO2 contributes more than half the increase in "relative forcing" over next 100 years, and it lasts much longer than the other gasses. It may be easier to regulate. Photosynthesis traps carbon, burning fuel releases it. Net primary production (the annual production of new plant tissue) captures 105 gigatons per year (54% on land and rest at sea)
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4 The oceans The oceans absorb CO2 by mixing surface water into the deep ocean. Thermohaline circuit (THC) is a major current system in the Atlantic Ocean. Gulf stream takes warm salty water from southern hemisphere northward, along the East coast of US and then northeast to Greenland, Iceland and Norway. The warm surface water is cooled by the cold air, increasing the density of the water and causing it to sink, creating a kind of vacuum which draws warm salty water from Gulf of Mexico, warming the air over the European continent.
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5 Weakening of Thermohaline Circuit? Greater snowmelts due to global warming, increasing the flow of cold freshwater (which is lighter than salt water) could reduce the conveyor effect (because there is less "sinking" of water), leading to a smaller vacuum effect. Cooler sea temperature could cause ice to form, creating a kind of lid over ocean, reducing the amount of cooling of the water, reducing the vacuum effect. The reflectivity (albedo) of the ice leads to more cooling in Europe Although a possible weakening or shutdown of THC is widely discussed in science community, there is disagreement about the likelihood of this event.
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The time-line of GHG (Greenhouse Gas) concentrations 70 million years ago, atmospheric CO2 concentrations were several times current levels. Atmospheric CO2 has ranged from 100 to 400 ppm over the past 20 million years. It has ranged from 180 - 290 ppm over the past 420,000 years, and between 270 - 290 ppm over last 2000 years, prior to industrial revolution. Current level about 380 ppm, an increase of about 30% from pre-industrial levels. About 75% of this increase due to fossil fuel burning, the remainder due to deforestation and industrial processes. 150% increase in methane concentration since pre-
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The science and economics of Climate Change2007 - The...

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