The ‘global warming hiatus’ that occurred between about 1998 and 2012 does not change our understanding of the influence of human activity on long-term warming, reports an Analysis in Nature this week.
Iselin Medhaug and colleagues review literature and reassess various models and observational evidence gathered since the so-called hiatus. During this period (1998-2012), Earth’s surface temperature did not seem to rise as expected from climate projections, and some models and observations seemed to be contradictory. These phenomena raised questions about our understanding of the climate system, at least in some quarters, including how well anthropogenic climate change and natural variability are understood. However, the authors find that different conclusions mostly result from the use of different datasets, different time periods and different definitions of a hiatus period. They demonstrate that, with appropriate treatment of models and observations, discrepancies can be reconciled.
More recent observations demonstrate that despite the apparent hiatus, the climate is continuing to warm, with 2015 and 2016 being the two warmest years on record. The authors conclude that the hiatus does not contradict our overall understanding of the climate system.
“Perhaps the most salient lesson to be learnt from work on the pause is the need for clarity of definition and for quantifiable, generalizable accounts of the alleged phenomenon,” writes James Risbey in an accompanying News & Views article. “Our definitions, like our tools, need sharpening if they are to sustain claims about unusual climate events.”