Recent global-warming hiatus tied to equatorial Pacific surface cooling

• Published in: Nature (London) 2013-09, Vol.501 (7467), p.403-407
• Main Authors: Kosaka, Yu, Xie, Shang-Ping
• Format: Article
• Language: English
• Subjects: 704/106/35; 704/106/694/674; 704/106/829/2737; Anthropogenic factors; Climate; Climate change; Climate models; Climate sensitivity; Climate variability; Climatology. Bioclimatology. Climate change; Cooling; Correlation coefficient; Drought; Earth, ocean, space; Environmental aspects; Exact sciences and technology; Experiments; External geophysics; Fluid dynamics; Forecasts and trends; Global temperature changes; Global temperatures; Global warming; Global Warming - history; Global Warming - statistics & numerical data; Greenhouse Effect - history; Greenhouse Effect - statistics & numerical data; Greenhouse gases; Heat; History, 20th Century; History, 21st Century; Humanities and Social Sciences; letter; Meteorology; Models, Theoretical; multidisciplinary; Ocean temperature; Pacific Ocean; Science; Sea surface temperature; Seasons; Seawater - analysis; Temperature; Time Factors; Trends
• ISSN: 0028-0836; 1476-4687
• DOI: 10.1038/nature12534

Global warming has stalled since the late 1990s, puzzling researchers; here a climate model that includes observed sea surface temperatures in the eastern equatorial Pacific reproduces the hiatus as part of natural variation, suggesting that long-term global warming is likely to continue. Pacific cooling puts global warming on hold Global warming has largely stalled since the late 1990s, raising concerns regarding our understanding of climate sensitivity, the underlying mechanisms influencing climate variability and the ability of climate models to represent decadal variability. Yu Kosaka and Shang-Ping Xie show that the warming hiatus, including most of its seasonal and spatial aspects, can be resolved when observations of recently observed cooling in the eastern equatorial Pacific are directly incorporated into a climate model. The results suggest that the current hiatus is a normal instance of internal climate variability, and that long-term warming is likely to resume as greenhouse gas concentrations continue to increase. Despite the continued increase in atmospheric greenhouse gas concentrations, the annual-mean global temperature has not risen in the twenty-first century 1 , 2 , challenging the prevailing view that anthropogenic forcing causes climate warming. Various mechanisms have been proposed for this hiatus in global warming 3 , 4 , 5 , 6 , but their relative importance has not been quantified, hampering observational estimates of climate sensitivity. Here we show that accounting for recent cooling in the eastern equatorial Pacific reconciles climate simulations and observations. We present a novel method of uncovering mechanisms for global temperature change by prescribing, in addition to radiative forcing, the observed history of sea surface temperature over the central to eastern tropical Pacific in a climate model. Although the surface temperature prescription is limited to only 8.2% of the global surface, our model reproduces the annual-mean global temperature remarkably well with correlation coefficient r = 0.97 for 1970–2012 (which includes the current hiatus and a period of accelerated global warming). Moreover, our simulation captures major seasonal and regional characteristics of the hiatus, including the intensified Walker circulation, the winter cooling in northwestern North America and the prolonged drought in the southern USA. Our results show that the current hiatus is part of natural climate variability, tied specifically to a L