. "2 The Challenge of Global Warming." The National Academies Summit on America's Energy Future: Summary of a Meeting. Washington, DC: The National Academies Press, 2008.
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The National Academies Summit on America’s Energy Future: Summary of a Meeting
FIGURE 2.1 Global air and ocean temperatures and sea level have risen over the course of the 20th century, while average annual snow cover in the Northern Hemisphere has declined. SOURCE: IPCC (2007; Figure 1-1).
anthropogenic greenhouse gas emissions show an increase in temperatures that closely tracks observations.
SCENARIOS OF FUTURE CLIMATE CHANGE
On the basis of models that assume different technology, economic, and policy trajectories, the IPCC has developed several scenarios of future emis-
