Emily Walton's List: GISAT Assignment 1

• In the combustion of biomass (e.g. wood, crop residues, dried dung), and fossil fuels (coal, oil and natural gas), the primary end product is the gas carbon dioxide.
• Also formed during the combustion process, under certain conditions and to a lesser extent, are small black particles which one can see (such as from diesel engines or lit candles with long wicks), and which have recently been recognized by scientists as a contributor to global warming.
• Black carbon or soot is a part of a larger type of emissions, both natural and manmade, called aerosols. These aerosols are very small particles that are suspended in our atmosphere. They can originate from natural sources such as salt spray formed during ocean wave processes, dust formed from the grinding and erosion of land surfaces, forest fires, and volcanic eruptions for example.
• The emissions diagram gives a simplified version of aerosol generation showing how they can enhance cloud formation and precipitation. This can have either a cooling or warming effect depending on a variety of other factors.
  
• For example, a large volcanic eruption can inject millions of tons of small light colored particles high into the atmosphere where they reflect sunlight back into space causing a cooling effect. This effect can be measured by a temperature drop on our planet's surface. When Mt. Pinatubo in the Philippines erupted in 1991, global average temperatures actually dropped a degree or two until the particles settled out and warming again resumed.
• Darker particles, however, directly absorb energy as any dark surface will do and therefore have a warming effect.
• The following illustration of ice (courtesy NASA) perhaps illustrates this best. The left image shows how sunlight is reflected from the white ice surfaces, and indeed, up to 90% of the incoming solar radiation is
  
    reflected back into space. It also shows that the darker water surface absorbs solar energy. The right hand image shows the effect of black carbon particles on ice. In this case the darker, dirty if you will, ice surface absorbs a significant portion of the sun's energy which will result in increased ice melt.
• That is, the melting ice forms darker water, which absorbs more energy, which in turn melts more ice.
  
• Most of this black carbon is of anthropogenic origin, that is, from the incomplete combustion of fossil fuel and biomass burning. Atmospheric and climate scientists are trying to improve their understanding of this effect since it is an important component of climate science, the development of climate models, and the warming we are experiencing today. According to the 2007 IPCC Fourth Assessment Report, p 163, emission estimates are approximately 8.1 megatons (8,100,000 tons) of carbon per year.
  

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• A noted geologist who coauthored the New York Times bestseller Sugar Busters has turned his attention to convincing Congress that carbon dioxide emissions are good for the Earth and don't cause global warming. Leighton Steward
• Fire, Ice and Paradise in a bid to show senators working on the energy bill that the carbon dioxide cap-and-trade scheme could actually hurt the environment by reducing CO2 levels.
• Much of the global warming debate has focused on reducing CO2 emissions because it is thought that the greenhouse gas produced mostly from fossil fuels is warming the planet. But Steward, who once believed CO2 caused global warming, is trying to fight that with a mountain of studies and scientific evidence that suggest CO2 is not the cause for warming. What's more, he says CO2 levels are so low that more, not less, is needed to sustain and expand plant growth.
• Trying to debunk theories that higher CO2 levels cause warming, he cites studies that show CO2 levels following temperature spikes, prompting him to back other scientists who say that global warming is caused by solar activity.
• if CO2 levels are cut, he warns, food production will slow because plants grown at higher CO2 levels make larger fruit and vegetables and also use less water. He also said that higher CO2 levels are not harmful to humans. As an example, he said that Earth's atmosphere currently has about 338 parts per million of CO2 and that in Navy subs, the danger level for carbon dioxide isn't reached until the air has 8,000 parts per million of CO2.

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