For the first time, researchers have been able to combine different climate models using spatial¹（空间的） statistics -- to project future seasonal² temperature changes in regions across North America. They performed advanced statistical³ analysis on two different North American regional climate models and were able to estimate projections⁴ of temperature changes for the years 2041 to 2070, as well as the certainty of those projections.

The analysis, developed by statisticians at Ohio State University, examines groups of regional climate models, finds the commonalities between them, and determines how much weight each individual climate projection⁵ should get in a consensus⁶ climate estimate.

Through maps on the statisticians' website, people can see how their own region's temperature will likely change by 2070 -- overall, and for individual seasons of the year.

Given the complexity⁷ and variety of climate models produced by different research groups around the world, there is a need for a tool that can analyze⁸ groups of them together, explained Noel Cressie, professor of statistics and director of Ohio State's Program in Spatial Statistics and Environmental Statistics.

Cressie and former graduate student Emily Kang, now at the University of Cincinnati, present the statistical analysis in a paper published in the International Journal of Applied⁹ Earth Observation and Geoinformation.

"One of the criticisms from climate-change skeptics is that different climate models give different results, so they argue that they don't know what to believe," he said. "We wanted to develop a way to determine the likelihood of different outcomes, and combine them into a consensus climate projection. We show that there are shared conclusions upon which scientists can agree with some certainty, and we are able to statistically¹⁰ quantify that certainty."

For their initial analysis, Cressie and Kang chose to combine two regional climate models developed for the North American Regional Climate Change Assessment¹¹ Program. Though the models produced a wide variety of climate variables, the researchers focused on temperatures during a 100-year period: first, the climate models' temperature values from 1971 to 2000, and then the climate models' temperature values projected for 2041 to 2070. The data were broken down into blocks of area 50 kilometers (about 30 miles) on a side, throughout North America.

Averaging the results over those individual blocks, Cressie and Kang's statistical analysis estimated that average land temperatures across North America will rise around 2.5 degrees Celsius¹² (4.5 degrees Fahrenheit) by 2070. That result is in agreement with the findings of the United Nations Intergovernmental Panel on Climate Change, which suggest that under the same emissions¹³ scenario¹⁴ as used by NARCCAP, global average temperatures will rise 2.4 degrees Celsius (4.3 degrees Fahrenheit) by 2070. Cressie and Kang's analysis is for North America -- and not only estimates average land temperature rise, but regional temperature rise for all four seasons of the year.