Beware the habitual El Niño hype

The world is once again in the grip of a semi-regular climate alarm. I’m not referring to the latest onset of the El Niño cycle, declared in action on July 4th by the United Nations, but the amplified rhetoric about the pace and scale of warming temperatures that always accompanies such El Niño periods. 

Do you remember what happened last time we had a record El Niño in 2015/16? Global temperatures increased rapidly – as they do during such an event – and, according to some, it was full speed ahead to a runaway thermal apocalypse … until global temperatures started to fall again.

Earlier this month, the world broke global temperature records for several days, inevitably leading to renewed speculation about the onset of runaway global warming. The Guardian asked if we have entered a more erratic and dangerous phase with the onset of an El Niño event on top of human-made global heating.

Well, not really, or at least not on the basis of the data we have so far. 

The global temperature data which started these claims are of course preliminary and are in any case a mixture of real data and input from models so a note of caution is needed. Nonetheless it is expected that the temperature records will be confirmed in coming months.

The real situation is, as they say, a little more complicated than many of the exaggerated claims.

In recent months the atmospheric circulation over the North Atlantic has been unusual. The Azores High – a semi-permanent area of high pressure – was much weaker than normal. To put this into context, for the past decade the Azores High was about or above average at this time of year. This years variation resulted in low wind speeds occurring at the same time as a so-called marine heatwave in the north Atlantic. 

The lower wind speeds lead to a reduction in the mixing of surface water with the cooler water below, allowing the sea surface temperatures to increase. Another consequence is a reduction in the transport of dust from the Sahara westward over the north Atlantic. Usually Saharan dust reflects solar radiation back into space before it reaches the ocean surface, thereby cooling it. Another contributing factor is the decreasing particulate pollution over the northern hemisphere as the air gets cleaner over Europe and North America.

Now add all those effects to the multi-decadal fluctuation of north Atlantic circulation and the consequential transport of heat about which we have a very incomplete understanding.

Then there is the El Niño starting to snake its way across Pacific equatorial waters. All of this is against a backdrop of a global warming trend which, aside from the El Niño, hasn’t shown much of an increase, if at all in almost the past decade.

So looking at the events of the past few months, and the records broken, you would have to say it’s complicated and best left to a post-El Niño analysis. No such caution for the Met Office and the Guardian however: “If a few decades ago, some people might have thought climate change was a relatively slow-moving phenomenon, we are now witnessing our climate changing at a terrifying rate,” they quote Prof Peter Stott, who leads the UK Met Office’s climate monitoring and attribution team.

Given the complexity and disparity of recent events I look forward to the Met Office’s post-El Niño analysis of such extreme and rather premature hype.