Climate Change Increased the Likelihood of the 2016 Heat Extremes in Asia
Introduction. Analyses of the observed monthly temperature record from the Goddard Institute for Space Studies (GISS) Surface Temperature Analysis (GISTEMP; Hansen et al. 2010) indicate that the total area that experienced extreme warmth over the global land surface in 2016 was record-breaking, exceeding the previous highest record in 2010 (Fig. 19.1a, fraction of area that experiences extremely high temperature). This frequent occurrence of warm events is particularly remarkable over the Asian region (Fig. 19.1a). Many parts of Southeast Asia, southern India, and northern Eurasia experienced extremely high temperature by the end of 2016 (Fig. 19.1b). In India, at least 580 people were killed by the heat waves from March to May (India’s government; European Commission). The record-breaking high temperature had been persistent more than 10 months in the Maritime Continent. In Thailand, the heat wave also caused a new record for energy consumption because of the nationwide usage of air conditioners (Gecker and Chuwiruch 2016). Generally, Southeast Asia experiences warm and dry conditions during El Niño, being in the region of anomalously downward motion associated with the weakened Walker Circulation. Also, the global surface warms up with a lag of several months following an El Niño event through persistent changes in atmospheric circulation (Trenberth et al. 2002). In this report, we investigate to what extent the 2016 extreme warmth across Asia was attributable to anthropogenic warming or to the major El Niño episode in 2015/16. Many studies have concluded that heat waves over the global land area have become more frequent due to human-induced global warming (e.g., Jones et al. 2008; Christidis and Stott 2014; Shiogama et al. 2016). To separate the influences of anthropogenic warming and natural variability on the 2016 heat events in Asia, we analyzed large ensembles of atmospheric general circulation model (AGCM) simulations with and without anthropogenic warming and ENSO effects.