‘Category-6' Supertyphoon Haiyan in Global Warming Hiatus – Two Sides of the Same Coin

With the extra-ordinary intensity of 170 kts (315 km hr^-1), super-typhoon Haiyan recently devastated the Philippines. This intensity is among the highest ever observed for tropical cyclones (TCs) globally [Knapp et al., 2010], 35 kts well above the threshold of the existing highest category of 5. Though there is much speculation to associate global warming with such extra-ordinary intensity, it is undeniable that we are currently in the global warming hiatus [Kosaka and Xie, 2013; England et al., 2014]. Observations show that global warming has paused for more than a decade [Kosaka and Xie, 2013; England et al., 2014]. It is thus puzzling why such an intense TC can occur during the hiatus. Here we show that though seemingly contradictory, they are actually ‘two sides of the same coin'. We found that it was the same La Niña-like decadal phenomenon which causes the hiatus also contributes to the extra-ordinary intensification of Haiyan. The three critical factors for Haiyan's severe damage and high intensity, i.e., high sea level rise, warm water accumulation, and fast travelling speed, were all found to be associated with the western Pacific manifestation of this phenomenon. Our results alert us the complexity in nature. Though we think that this La Niña-like decadal phenomenon is to cool the planet via offsetting the global warming [Kosaka and Xie, 2013], it actually has another side of manifestation, the ability to fuel the most intense super-TC over the Asia Pacific region.