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A worldwide panel assesses the science

As human activities affect our atmosphere, societies are beginning to brace for significant climate change. But is science sophisticated enough to predict what our climate will look like in coming decades? And can it single out how a specific region, such as the Midwest, will be affected?

The threat of climate change is so important that researchers across the world have joined forces under the auspices of the Intergovernmental Panel on Climate Change to answer such questions. Created in 1988 by the World Meteorological Organization and the U.N. Environment Programme, the IPCC represents an unprecedented effort to assess climate change research and advise policy makers on options to mitigate and adapt to future climate. NCAR scientists, working with hundreds of colleagues across the United States and overseas, are laying the groundwork for a new assessment in 2007.

“Climate change respects no national boundaries,” explains Thomas Stocker, a climate researcher with the University of Bern in Switzerland who is working closely with NCAR scientists on the upcoming assessment. “It is a global problem, caused primarily by the industrialized nations, but its damages are felt locally. Hence, scientists from all regions of this planet must be involved in climate research.”


This NASA visualization of satellite data shows areas of unusually warm temperatures (in red) during the brutal European heat wave in 2003 that took thousands of lives. (Image by Reto Stöckli and Robert Simmon of the NASA Earth Observatory, based on data from the MODIS land team.)

A crucial model

NCAR plays a central role in the IPCC reports. The IPCC relies on the NCAR-based Community Climate System Model, along with oher leading models in the world, for computer-generated simulations of future climates. The most recent version of the model, known as the CCSM3, indicates that global temperatures would climb by 2.3 degrees Celsius (4.4 degrees Fahrenheit) in a hypothetical scenario in which atmospheric levels of carbon dioxide are doubled from present-day values by the year 2100.

The CCSM also simulates past events, such as the climate during the Last Glacial Maximum, an ice age event about 18,000 years ago. By comparing the model results to records from ice cores and other sources, researchers can verify the accuracy of the model, while studying whether past climate patterns hold clues to the future.

In addition, NCAR scientists help to organize the assessments, recruit scientists from both industrialized and developing countries to participate, and edit chapters.

“The scientists at NCAR are leading experts in many areas relevant to climate change,” Stocker says. “Their expertise, combined with the institution’s computational and human resources, makes NCAR the most important provider worldwide of state-of-the-art community climate models.”


Among the NCAR scientists working on the next IPCC assessment are (from left) William Collins, Gerald Meehl, Elisabeth Holland, Kevin Trenberth, and Linda Mearns. (Photo by Carlye Calvin, ©UCAR.)

Stocker and NCAR scientist Gerald Meehl, for example, are convening lead authors of the chapter on future climate. The chapter describes model simulations looking as far as 300 years into the future, based on various scenarios of emissions of carbon dioxide and other gases. To ensure a global perspective, the chapter’s 14 authors are drawn from countries as diverse as Great Britain, Chile, Senegal, and China.

“The IPCC really is conscious of international balance,” Meehl explains.

NCAR’s Kevin Trenberth and Philip Jones of the University of East Anglia, England, are serving as convening lead authors of the chapter on weather observations going back 150 years. Their co-authors for that chapter include researchers in Argentina, Germany, Iran, Kenya, and New Zealand, among other countries.

Additional IPCC efforts involving NCAR scientists include looking into such issues as the climatic impacts of land cover and assessing the methodologies used to characterize future conditions.

Authoritative voice

The IPCC has emerged as the most authoritative voice on the issue of global climate change. Its detailed assessments, which are issued every five to seven years, are an important tool for both policy makers and scientists.

quoteAs research into climate change has become more sophisticated, IPCC assessments have warned that human activities are clearly affecting the climate. As far back as 1995, the second assessment stated, “The balance of evidence suggests that there is a discernible human influence on global climate.” The third assessment, issued in 2001, strengthened this warning, stating that human-produced greenhouse gases “have contributed substantially to the observed warming over the last 50 years.”

The 2007 assessment is expected to put greater focus on such issues as how climate change is likely to affect specific regions and what strategies societies can use to adapt. It will also look at what may happen to global climate after 2100 if concentrations of carbon dioxide and other greenhouse gases are stabilized.

The IPCC reports have become an important teaching tool in science classrooms. “It’s a fantastic reference document to hand to graduate students,” Meehl says. “In one volume, you basically have a summary of climate science.”



Atmospheric disturbances can trigger severe weather thousands of miles away. (Photo from the UCAR Digital Image Library.)

When a cyclone formed off Japan at the beginning of August 2002, few forecasters anticipated its ultimate impact. The storm set off a series of planetary waves in the atmosphere that sparked unsettled conditions and, within 10 days, caused central Europe to be buffeted with torrential rains.

As atmospheric scientists seek to piece together such patterns that affect weather conditions across the globe, they have formed an international research and development program under the auspices of the World Meteorological Organization. The program, THORPEX, aims to improve the accuracy of 1- to 14-day forecasts by enhancing cooperation between national agencies and guiding research initiatives.

“This is a high-level degree of collaboration to improve global forecasts,” explains NCAR scientist David Parsons, the North American co-chair of the program. “No country can do this on its own because it requires measurements around the world.”

One major goal of THORPEX is to study the results of combining computer forecasts from various operational centers into a grand forecasting ensemble that exceeds the capabilities of any single national center. Whereas many countries now produce their own forecasts for global conditions, the data will be shared under THORPEX to produce larger ensembles of forecasts, providing scientists with more information to predict weather conditions.

Another major goal is to coordinate research programs to learn more about atmospheric events that lead to severe weather. Scientists from many countries, for example, are joining efforts under THORPEX to collect data on regional conditions over Africa that trigger hurricanes in the Atlantic Ocean. They will also take additional measurements in the upper latitudes to learn more about cold air masses that sweep over North America, sometimes causing severe winter storms.

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Clues from the Stratosphere

The Subtleties of Human Impacts

The Role of the Oceans

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