The National Academies Summit on America's Energy Future Summary of a Meeting (2008) / Chapter Skim
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2 The Challenge of Global Warming
2 The Challenge of Global Warming
Pages 11-19
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From page 11... ...
Deforestation and the burning of fossil fuels have increased the amount of carbon dioxide in the atmosphere from about 300 parts per million in 1900 to about 380 parts per million today. This increase has been driven by a fourfold increase in global population -- to more than 6 billion -- combined with an increase in the per capita use of energy.
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From page 12... ...
. bitmap image low resolution anthropogenic greenhouse gas emissions show an increase in temperatures that closely tracks observations.
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From page 13... ...
Temperature anomaly (°C) 1900 1950 2000 1900 1950 2000 1900 1950 2000 Year Year Year models using only natural forcings observations models using both natural and anthropogenic forcings FIGURE 2.2 Models that incorporate both natural and human causes of climate change more accurately predict temperatures over the past century as shown by the fit between the predictions of such models 2-2.eps and observed temperatures (black lines)
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From page 14... ...
Even if all use of fossil fuels were to cease today, these models predict another 0.6-degree centigrade increase in temperature during the 21st century, Davis observed. Since all of the IPCC scenarios assume continued use of fossil fuels, all of the scenarios assume temperature increases larger than that amount.
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From page 15... ...
"The problem is growing more severe, with adverse impacts that are perhaps somewhat different and certainly occurring much more quickly than we had perhaps anticipated as recently as 3 or 4 years ago." STEPS TO BE TAKEN Without major policy changes, emissions of carbon dioxide will continue to increase in future years. In the IPCC scenario that assumes no policy interventions for reducing greenhouse gas emissions (the "reference scenario" in Figure 2.5)
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From page 16... ...
‡Based on average rate of sea level rise of 4.2 millimeters per year from 2000 to 2080. SOURCE: IPCC (2007; broadside Figure 3-6)
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From page 17... ...
Various policy initiatives discussed in the rest of this summary will be needed to reduce carbon dioxide emissions. Stabilizing concentrations of carbon dioxide in the atmosphere will be an even greater challenge, Davis said.
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From page 18... ...
And the final 20 percent is accounted for by the troubling observation that sinks responsible for absorbing carbon dioxide from the atmosphere appear to be less effective today than they were in the past. For example, changes in wind patterns in the Southern Hemisphere have caused carbon-rich water to stay close to the surface, which means that less carbon dioxide can be absorbed into the oceans.
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From page 19... ...
We need an integrated assessment of what those pathways are like." Improving modeling capabilities will contribute to the development of strategies that involve energy technology choices and efforts to develop new technology options. In these efforts, independent advice from groups like the National Academies will be absolutely essential, according to Davis.
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