Combination of temperature rises linked to greenhouse gas emissions and El Nino could send mercury levels soaring
By Gerard Wynn
The latest global data show that record surface temperatures last year have continued into 2015, and rising.
Last year was the hottest yet, in a temperature record dating back to around 1850, according to the World Meteorological Organisation (WMO).
But global average surface temperature for January and February in 2015 broke new records, compared with past annual averages (see figure below).
Temperatures are rising mostly thanks to greenhouse gas emissions. They will keep rising, without very substantial cuts in annual emissions.
But there is an additional factor at play just now. The “El Nino” weather cycle originates in the Pacific Ocean, and has various effects including raising average temperatures.
I was advised by a climate scientist that we will find out very soon (April/ May) whether the present weak El Nino will intensify or die away.
El Nino is characterised by above-average sea surface temperatures (SST) in the equatorial Pacific Ocean. A graphic here shows how temperatures have recently risen in the eastern Pacific, off the coast of Central America.
Does that mean El Nino will intensify? We may find out soon.
Another feature of El Nino is strong westerly winds in the western Pacific.
The more negative the daily Southern Oscillation Index, recorded here, the more likely westerly winds will strength and El Nino intensify.
El Nino doesn’t simply matter to climate scientists following global average temperatures.
Among its consequences are increased rainfall across southern U.S. and in Peru, which has caused destructive flooding in the past, and drought in the West Pacific, sometimes associated with devastating brush fires in Australia.