Federal Report Supports Climate Change Models

By Jim Dawson
Inside Science News Service

 

The global climate models that scientists use to try to predict the Earth’s climate change have steadily improved over the past decade and are one of the "great success stories of scientific simulation," according to a report released Thursday by the U.S. Climate Change Science Program.

 

"Climate models have become an essential tool in helping us understand the nature and implications of climate change," said David Bader, a climate scientist with the Lawrence Livermore National Laboratory and a lead author of the report.  There are about 20 different types of global climate models (GCMs) being run worldwide, with three being operated by U.S. researchers. The new report describes these models and their ability to simulate the Earth's climate.

 

Researchers who wrote the report over the past three years noted that the models have "matured" to the point where they are good at predicting El Nino-Southern Oscillations, a complex ocean-atmosphere interaction that results in climate-altering heating in the southern Pacific off the coast of South America.

 

Bader also said that the models have looked back at 20th Century climate as a way to evaluate pieces of models and the models comprehensively together, so that the predictions can be compared between the models and observed climate data.  Models taking into account solar variations, volcanic and human-produced aerosols, and greenhouse gases "are able to simulate the 20th Century mean global temperature," he said.

 

That 20th Century signal, particularly over the past several decades, "cannot be simulated without including the anthropogenic [human-contributed] effect," he said. The report notes that without the human contribution to global warming, the models indicate the planet would have actually cooled during the past 20 years.

 

Although the report doesn't "get into actual projections of future climate change . . . the extensive review of current literature of the 20th Century trends is pretty consistent between the models and observations," Bader said. "And we show that you cannot get those trends correct when compared against observation without including anthropogenic effects."

 

Of those who remain skeptical of the accuracy of the models, Bader said the report "just provides further evidence that those who are of that view are in a very small minority, in that the evidence is pretty convincing."

 

Although the report cites many limitations in the models, the overall endorsement by government and university scientists of the growing accuracy and value of the models is important in the wider political debate over the urgency of the global warming problem.  The researchers said today’s report is intended to inform the debate about global warming among both the public and policy makers.

 

The report, the 10th in a series of 21 scheduled reports on global warming by the federal climate change program, was developed by the Department of Energy.