Editorial: "It's time we sorted out climate 'blips'"
FOR the first time, the forecast from a climate model has been put to the test. It passed with flying colours ? accurate to within a few hundredths of a degree.
The prediction was made in 1999, based on data collected before 1996, and comes from one of several models used by the International Panel on Climate Change (IPCC) to predict the outcomes of different warming scenarios. But sceptics claimed that it was wrong because it failed to predict the recent slowdown in the rate of warming.
To address the claims, Myles Allen at the University of Oxford and colleagues compared the forecast with actual temperature trends. The forecast predicted that the world would warm by 0.25 ?C between the decade to 1996 and the decade to 2012. This was exactly what happened, says Allen (Nature Geoscience, doi.org/k24).
The recent stalling of warming is certainly real; in January the UK's Met Office predicted that annual global temperatures over the next five years will be on average 0.43 ?C higher than the average for 1970 to 2000, down from its previous prediction of a 0.54 ?C rise. But rather than undermining the forecast, the slowdown bolsters it, says Allen. That's because natural fluctuations caused temperatures to get ahead of the prediction in the final years of the 20th century, so when the current hiatus is taken into account, the net result is the same as the forecast.
However, if global temperatures remain stable until 2016, then the 1999 forecast would be little better than a random prediction, the study finds. And if they stay stable until 2026, the model would be wrong.
Critics say the modellers are congratulating themselves too much. Roger Pielke Jr at the University of Colorado, Boulder, accuses them of being slow to admit the slowdown. "They should ask why it took so long to acknowledge what has been apparent for some time," he says.
The hiatus is influencing some revised assessments of future temperatures. In February, the study's co-author, Peter Stott of the Met Office, reported that global temperatures were following the "lower ranges" of most model forecasts, making it less likely we will experience the highest projections of temperature.
This article appeared in print under the headline "First climate model forecast comes true"
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