NASA News & Feature Releases

Opportunity to Avoid Extreme Climate Changes within Reach

According to a paper presented Thursday by NASA Researcher Dr. James Hansen, declining greenhouse gas growth rates lends credibility to measures designed to control worldwide emissions, such as the Kyoto Treaty. Dr. Hansen presented his paper, "Common Sense Climate Index: Is Climate Changing Significantly," at yesterday's annual meeting of the American Geophysical Union in San Francisco.

Hansen's research reveals that forecasts showing a doubling of carbon dioxide (CO2) levels in the atmosphere are not inevitable, but could still occur if developed nations continue their current trends in emissions and developing nations continue to increase their emissions of CO2 to the level of the developed world. A decrease in the growth of worldwide emissions of greenhouse gases through an international treaty provides a unique opportunity to avoid extreme climate changes that would accompany continued increases in carbon dioxide and other greenhouse gases.

However, climate change is still real and greenhouse gases emissions will not decrease without an international agreement. The Kyoto Treaty becomes even more imperative based on this research, since it appears possible that the levels of greenhouse gas emissions could be realistically reduced in the years ahead.

While temperature levels around the world continue to steadily increase, increases in carbon dioxide levels in the atmosphere have been leveling off while methane (CH4) increases have plummeted and chlorofluorocarbons (CFC) increases have practically ceased according to this new research. While an international treaty (Montreal Protocol) restricting CFC use around the world is responsible for the steadying levels of CFCs in the atmosphere, it is not well understood why the growth rate of CH4 is decreasing and the growth rate of CO2 has leveled off.

"The change in the growth rates is good news because they make it plausible that we may be able to avoid the most drastic climate changes," said Dr. James E. Hansen, Chief of the Goddard Institute for Space Studies (GISS), New York, a division of NASA's Goddard Space Flight Center, Greenbelt, Md. "But they are also a warning that we need the research to understand all the processes that effect these greenhouse gas growth rates."

The researchers describe the slowdown in the greenhouse has growth rates as an opportunity to avoid extreme climate change. Specifically, they argue that doubled carbon dioxide in the 21st Century is not inevitable if serious efforts to reduce greenhouse gases are made by both developed and developing countries, although it could still occur if developing countries follow an exponential growth curve in carbon dioxide emissions or if the rest of the world continues to significantly increase its greenhouse gas emissions.

Media Contacts

Leslie McCarthy, NASA Goddard Institute for Space Studies, New York, N.Y., 212-678-5507,