Global warming has been the hottest topic in recent climate change studies. It can affect the global hydrological cycle, atmospheric circulation and extreme weather, thus it is critically important to every life on the earth. However, the warming is not spatially uniform throughout the global ocean, even some regions occur cooling signals. It is worth noting that there exists a significant cooling trend in the eastern tropical Pacific sea surface temperature (SST) during recent decades, which is proved to be the key to the current global warming hiatus. Therefore, understanding the mechanism responsible for the cooling signal in the eastern tropical Pacific under the global warming background is of crucial importance to climate change studies.

ZHOU Tianjun and his research team at the Institute of Atmospheric Physics (IAP), explored the effects of global warming due to the increased greenhouse gases (GHGs) and found that it cannot explain the cooling in the eastern tropical Pacific during recent three decades. Thus other mechanisms in addition to global warming likely exist to account for the phenomenon. They further examine the effects of the most important decadal variability of the climate system, Interdecadal Pacific Oscillation (IPO) and Atlantic Multidecadal Oscillation (AMO), in forming the recent cooling in the eastern tropical Pacific Ocean. The results show that the cooling trend is preliminarily dominated by the phase transition of IPO from positive to negative phases during this period, which overwhelms the effect of global warming. In addition, the phase transition of AMO during this period causes a weak warming trend in the eastern tropical Paci?c and makes the trend along the equator less signi?cant in observation (Fig. 1).

Fig. 1 The effects of global warming mode, IPO mode and AMO mode in global SST from four different datasets of HadISST, Kaplan_v2, ERSST_v3, and HadSST2.

The finding is recently published online in Journal of Geophysical Research: Atmospheres.

Reference:

Dong Lu, Tianjun Zhou*, 2014: The formation of the recent cooling in the eastern tropical Pacific Ocean and the associated climate impacts: A competition of global warming, IPO and AMO, Journal of Geophysical Research - Atmospheres, DOI: 10.1002/2013JD021395, in press.