El Niño Southern Oscillation index: duration and intensity of La Niña and El Niño years. El Niño is usually defined as a positive temperature anomaly in the east and central tropical Pacific. Another way to express the climate phenomenon is through an index (Southern Oscillation index) for air pressure difference across the equatorial Pacific – with relatively high pressure in the West and low pressure (because of increased convection over warm water) in the East typical for El Niño. The above graph uses that alternative indicator – and it holds a clue to our temperature predictions for 2014 and 2015: hottest year on record, followed by the hottestest year on record…
If we take another look at the IRI ensemble forecast for El Niño some members show a clear and speedy rise in East Pacific tropical ocean temperatures. Before we conclude ‘El Niño ahead’ during northern hemisphere summer and autumn let’s not ignore that a handful* of the 23 climate models show only a weak increase in water temperatures, staying below the official El Niño threshold (+0.5C).
[*) We all know an average hand can hold around 7 climate models – which means some 70 percent of models say El Niño, whereas 30 percent says somewhat warmer (up to half a degree), but still neutral ENSO.]
Well then, is there any way of telling which of the climate models may be more inclined to predict actual climatic events for upcoming months? Yes, probably there is:
According to NOAA’s NCEP climate prediction model the Pacific Niño 3.4 region may experience more than a +1.5 degrees Celsius sea surface temperature anomaly, then officially qualifying as ‘strong El Niño’ – shown in graph below.
Compared to last month’s forecast the IRI climate model ensemble shows a somewhat faster development of a positive ENSO state and clear indications of El Niño conditions, during the boreal summer of 2014, possibly already passing the +0.5C threshold for tropical East-Pacific sea surface temperature anomaly by June – as most leading models (NCEP, JMA, NASA, ECMWF) indicate.
The second part of the new IPCC report, about the impacts of climate change, has been released on Monday. Across the globe dutiful journalists filled the headlines of their newspapers – and as they presume most of their readers are human – focus heavily on the social implications, especially concerns for the human food supply, through a decrease in net agricultural productivity, firstly (from 1-2 degrees warming) in the tropics, and under current global emission trends (possibly even exceeding 4 degrees) also at high latitudes.
The authors conclude therefore that – as doubling of the current warming is already inevitable – the world climate policy should not just focus on reducing emissions, but also on adapting to warming – a message easily misinterpreted as ‘hey, I heard we can adapt, so that’s cool – with our lifestyle and economy and all’.
But written in between the lines of the summary for policy makers the report contains a much more dire warning – not a worry for its human inhabitants directly, but for the entire Earth, as a life-bearing planet: the Holocene Mass Extinction.