Global Warming

Pursuant to a congressional request, GAO examined global warming research and policy issues, focusing on: (1) the increase in greenhouse gases; (2) the strengths and limitations of enhanced global warming estimates; and (3) possible policy responses to address global climate change.

GAO found that: (1) although carbon dioxide was responsible for almost half of the enhanced greenhouse effect, combinations of other gases had a comparable effect on global warming; (2) although atmospheric levels of greenhouse gases increased over time, their future growth rates were uncertain due to a lack of sufficient information; (3) scientists needed a better understanding of processes controlling greenhouse gases, along with improved observational data on their atmospheric concentrations; (4) general circulation models (GCM) estimated an increase in the average global temperature over the next century with the radiative equivalent of a doubling of carbon dioxide; (5) such GCM limitations as widely spaced grids, oversimplification of natural processes, poor or no representation of climate feedbacks, and exclusion of ocean processes hindered scientists' ability to accurately study regional effects of global warming; (6) scientists expected such GCM improvements as increased research efforts and more observational data and computer resources; (7) the United States and over 35 other nations and organizations established an international panel to respond to global warming; (8) Congress introduced over 20 bills to address global warming; (9) policymakers looked at adaptive strategies that involved adjusting the environment to reduce the consequences of a changing climate and at such limitation strategies as improving energy efficiency, replacing fossil fuels with renewable energy sources, limiting reforestation, and increasing use of nuclear energy; and (10) although the federal government had several options to reduce greenhouse gas emissions, actions were desirable as soon as possible due to lengthy policy development and implementation schedules.