Can climate models explain the recent stagnation in global warming?


In recent years, the increase in near-surface global annual mean temperatures has emerged asconsiderably smaller than many had expected. We investigate whether this can be explained bycontemporary climate change scenarios. In contrast to earlier analyses for a ten-year period thatindicated consistency between models and observations at the 5% confidence level, we find thatthe continued warming stagnation over fifteen years, from 1998 -2012, is no longer consistentwith model projections even at the 2% confidence level. Of the possible causes of theinconsistency, the underestimation of internal natural climate variability on decadal time scales isa plausible candidate, but the influence of unaccounted external forcing factors or anoverestimation of the model sensitivity to elevated greenhouse gas concentrations cannot be ruledout. The first cause would have little impact of the expectations of longer term anthropogenicclimate change, but the second and particularly the third would.
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