How much longer can the Bush Administration maintain its current attitude to global warming?
Climate Change Testimony of Ralph J. Cicerone
Ralph Cicerone, a climate scientist and the new head of the National Academy of Sciences, testified before a Senate Commerce subcommittee on global climate change on July 20. His oral testimony follows. His more detailed written testimony can be seen at the National Academies web site.
CLIMATE CHANGE SCIENCE AND RESEARCH:
RECENT AND UPCOMING STUDIES FROM THE NATIONAL ACADEMIES
Statement of
Ralph J. Cicerone, Ph.D.
President, National Academy of Sciences
The National Academies
before the
Subcommittee on Global Climate Change and Impacts
Committee on Commerce, Science, and Transportation
U.S. Senate
July 20, 2005
Good morning, Mr. Chairman and members of the Committee. My name is Ralph Cicerone, and I am President of the National Academy of Sciences. Prior to this position, I served as Chancellor of the University of California at Irvine, where I also held the Daniel G. Aldrich Chair in Earth System Science. In addition, in 2001 I chaired the National Academies committee that wrote the report, Climate Change Science: An Analysis of Some Key Questions, at the request of the White House.
This morning I will summarize briefly the current state of scientific understanding on climate change, based largely on the findings and recommendations in recent National Academies’ reports, focusing especially on the 2001 report that I chaired and the 2003 report Implementing Climate and Global Change Research, in which the U.S. Climate Change Science Program strategic plan was reviewed. These reports are the products of a study process that brings together leading scientists, engineers, public health officials and other experts to provide consensus advice to the nation on specific scientific and technical questions. The recent statement on climate change issued by the G8 countries, China, India, and Brazil is also based on findings in these and other reports of the National Academies.
I. SCIENCE OF CLIMATE CHANGE
The Earth is warming. Weather station records and ship-based observations indicate that global mean surface air temperature increased about 0.7oF (0.4oC) since the early 1970’s (See Figure). Although the magnitude of warming varies locally, the warming trend is spatially widespread and is consistent with an array of other evidence (e.g., melting glaciers and ice caps, sea level rise, extended growing seasons, and changes in the geographical distributions of plant and animal species). The ocean, which represents the largest reservoir of heat in the climate system, has warmed by about 0.12oF (0.06oC) averaged over the layer extending from the surface down to 750 feet, since 1993.
Laboratory measurements of gases trapped in dated ice cores have shown that for hundreds of thousands of years, changes in temperature have closely tracked atmospheric carbon dioxide concentrations. Burning fossil fuel for energy, industrial processes, and transportation releases carbon dioxide to the atmosphere. Carbon dioxide in the atmosphere is now at its highest level in 400,000 years and continues to rise. Nearly all climate scientists today believe that much of Earth’s current warming has been caused by increases in the amount of greenhouse gases in the atmosphere, mostly from the burning of fossil fuels. In fact, recent analyses of measurements of the Sun’s total brightness argue against any detectable long-term trend in the energy Earth receives from the Sun, making it difficult to conclude that the Sun has been responsible for the warming observed over the past 25 years.
Carbon dioxide can remain in the atmosphere for many decades and major parts of the climate system respond slowly to changes in greenhouse gas concentrations. The slow response of the climate system to increasing greenhouse gases also means that changes and impacts will continue during the twenty-first century and beyond, even if emissions were to be stabilized or reduced in the near future.
Simulations of future climate change project that, by 2100, global surface temperatures will be from 2.5 to 10.4oF (1.4 to 5.8oC) above 1990 levels. Pinpointing the magnitude of future warming is hindered both by remaining gaps in understanding the science and by the fact that it is difficult to predict society’s future actions, particularly in the areas of population growth, economic growth, and energy use practices. Other scientific uncertainties about future climate change relate to the regional effects of climate change and how climate change will affect the frequency and severity of weather events.
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