Predicting the climate of the 21st century

Warming land and ocean surfaces, melting glaciers, rising sea levels, and other recent evidence strongly suggest that Earth’s climate is already changing rapidly because of the buildup of greenhouse gases in the atmosphere, according to Warren Washington, senior scientist and head of the Climate Change Research Group at the National Center for Atmospheric Research (NCAR). Computer models of Earth’s climate support these observations, he says, and indicate more severe changes yet to come.

Even if societies successfully cap worldwide greenhouse gas emissions, the global climate will continue to warm into the 22nd century, though at a slower rate than if no attempt is made to control the emissions, Washington says. Policy makers must prepare to adapt to a changing climate even while slowing the greenhouse gas buildup, he says. Washington will present these conclusions in his talk, “Predicting the Climate of the 21st Century,” at the annual meeting of the American Association for the Advancement of Science in Denver on February 16.

“Scientific confidence in the ability of models to project future climate has increased,” says Washington. “Meanwhile, recent experiments and routine monitoring have found evidence of global climate changes already occurring that are much larger than can be explained by the climate’s natural variability.” In his talk, Washington will explain how a computer model of global climate works and highlight what the most sophisticated models in the United States and elsewhere are now telling us about present and future climate.

A rise in the average global temperature is a convenient marker to indicate changes in actual climate extremes that affect our environment, says Washington. For example, heat waves, as well as floods and droughts, will become more severe and occur more often. The first freeze dates will arrive later, and hard freezes will become less frequent in some areas. Rainfall and snowfall will increase or decrease, depending on the region. The difference between daily high and low temperatures will shrink in many areas as average temperature rises. Such climate changes occurring around the globe are likely to affect disease and health patterns and threaten ecosystems, with important implications for forest survival, food supply, biodiversity, land use, and pollution.

“We are already seeing many of these changes,” says Washington. “The debate on whether climate change is occurring has ended. The question is how much will take place and what are its impacts.”

ABOUT THE PRESENTER: Warren Washington is an internationally recognized expert in atmospheric science and climate research and a pioneer in computer modeling of Earth’s climate. He was appointed to the National Science Board in 1994, reappointed in 2000, and elected its chair in May 2002. The board has dual responsibilities as national science policy adviser to the president and Congress and as governing board for the National Science Foundation. Washington has advised five administrations, from presidents Jimmy Carter through George W. Bush. He has served on numerous boards and committees and has garnered many awards for his scientific achievements. Washington has conducted scientific research on staff at the National Center for Atmospheric Research since 1963.

ON THE WEB: For a more complete biography of Warren Washington, see http://www.cgd.ucar.edu/ccr/warren.

The University Corporation for Atmospheric Research manages the National Center for Atmospheric Research under primary sponsorship by the National Science Foundation. Opinions, findings, conclusions, or recommendations expressed in this publication are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.