Contributions of atmospheric circulation variability and data coverage bias to the warming hiatus

• Published in: Geophysical research letters Vol. 42; no. 7; pp. 2385 - 2391
• Main Authors: Saffioti, Claudio, Fischer, Erich M., Knutti, Reto
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 16.04.2015; John Wiley & Sons, Inc
• Subjects: Accounting; Anthropogenic factors; Area; Asymmetry; Atmospheric circulation; Atmospheric models; Bias; Circulation; Climate; Climate models; Cooling; coverage bias; Data; dynamical adjustment; Estimates; Hemispheric laterality; Intercomparison; internal climate variability; Loads (forces); Meteorology; natural climate variability; Natural variability; Northern Hemisphere; Seasons; Temperature; Temperature effects; Temperature trends; Trends; Variability; warming hiatus; Winter; Northern Hemisphere
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2015GL063091

The warming hiatus shows a strong seasonal and geographical asymmetry, with cooling in the Northern Hemisphere winter, especially over land, and warming elsewhere and in the other seasons. We show that the characteristics of the Northern Hemisphere winter cooling in 1998–2012 can mostly be explained by missing observations and by internal variability in the atmospheric circulation of the Northern Hemisphere extratropics. Estimates of the annual and seasonal temperature trends in 1998–2012 obtained by considering the concurrent effects of unforced natural variability and of coverage bias are much closer to the corresponding long‐term trends. Reanalyses suggest that the coverage bias was exceptionally pronounced during recent years and that an area of strong warming was missed due to the incomplete observational coverage. Coupled Model Intercomparison Project Phase 5 climate models indicate that trends in atmospheric circulation during the hiatus period did not occur as a response to anthropogenic forcing. Key Points Atmospheric circulation contributed to the observed boreal winter cooling Recent winter cooling is overestimated due to incomplete observational coverage Accounting for both implies positive corrections to temperature trends