The claim that climate models systematically overestimate the warming effects of greenhouse gases seems to be unfounded. Reuters

Doubters of the man-made global warming theory who point out that increases in global temperatures are not constant and question the authenticity of computerized climate models that scientists use to predict future temperatures, may now have a new theory to contend with. A new study has suggested there is no evidence of systematic errors in climate models.

According to researchers, many climate models do not predict a slowdown in global warming because they struggle to forecast random short-term changes in the planet's climate, but they're quite accurate in predicting long-term change. In the new study, published last week in the Journal Nature, Jochem Marotzke of the Max Planck Institute of Meteorology in Germany and Piers M. Forster of the University of Leeds in the U.K. explained how global temperature trends simulated by computer models in the past matched up to reality.

“Most present-generation climate models simulate an increase in global-mean surface temperature (GMST) since 1998, whereas observations suggest a warming hiatus,” researchers said in the study. “Here we analyse simulations and observations of GMST from 1900 to 2012, and show that the distribution of simulated 15-year trends shows no systematic bias against the observations.”

As part of the study, researchers examined how 114 simulations published in last year’s assessment report of the U.N. Intergovernmental Panel on Climate Change (IPCC) performed against real temperatures in every 15-year period since 1900. By testing how these models and their predictions compared with reality, researchers found that each 15-year interval’s actual temperature trend fell within a model's prediction range for that period, the Washington Post reported.

There were also instances when actual temperature trends for the 15-year periods could be found toward the extremities of the predicted ranges. However, the trends were not consistently at the higher or lower ends. And while the IPCC models did not accurately predict the recent hiatus in warming, they also underestimated warming in some 15-year periods, suggesting that climate change doubters were “cherry-picking” examples to reason that such models failed to predict the recent slowdown in warming, according to the Post.

The researchers said that a major factor influencing variations in the models' predictions were random fluctuations in the climate system, adding that while the climate models may not accurately predict short-term changes in global temperatures, they are useful in providing a glimpse into the long-term future.

“The differences between simulated and observed trends are dominated by spontaneous climate variability,” researchers said in a statement. “The claim that climate models systematically overestimate the warming caused by increasing greenhouse-gas concentrations therefore seems to be unfounded.”