Climate Attribution: Learning the Lesson of June 2019

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July 2nd, 2019

The ‘Spanish Plume’ which enveloped much of western Europe over the past week has now begun to dissipate with more seasonally normal temperatures spreading southwards across the continent as cooler Atlantic air once again invades the continent.

Paris, so much of a focus during the heatwave as a result of its previous experience in 2003, is now more comfortable with temperatures in the 20s. Further east in the Balkans values in the mid 30s still prevail, but the record breaking temperatures of last week are unlikely to be exceeded.

Five countries last week saw their temperature records broken, some by substantial amounts. Nimes in France registered a maximum of 45.9oC, a full 1.5oC above the previous national record.

Europe as a whole experienced its warmest June since 1880, a full 3oC above its June average of a century ago. Clearly things have changed dramatically in terms of climate extremes.

The question on everybody’s lips is to what extent this event was a manifestation of the ongoing climate change the planet is experiencing, or whether it was just another extreme that occurs occasionally in the existing climate regime.

Until quite recently, the answer given by climatologists would have been fairly conservative: ‘this is the kind of event which can be expected to occur more frequently as a result of climate change, though we can’t ascribe a particular event to climate change without some time to investigate.’

Times, however, have changed.

With the advent of faster and more powerful computers, the days of the single run climate model are now gone. Instead of running one, or a few models, to simulate present and future climate characteristics, we can now run multiple models.

In particular, models can be run using a pre-industrial atmosphere, and then rerun using an atmosphere with 415ppm Carbon dioxide. Comparing the frequency of extreme events under both runs enables a conclusion to be drawn on how likely a particular extreme will occur now as opposed to past times.

Far from waiting for many months for such results, teams of researchers are now waiting to plug in particular events to their programmes and can come up with conclusions very quickly.

Already, preliminary conclusions exist that the June heatwave conditions are likely to be occurring from now on multiple times more likely than a century ago.

The implications for health, agriculture and water supplies are obvious. It is perhaps heatwaves like this one that will catalyse the public perception of climate change and the urgent need for mitigation and adaptation.

The realisation that June 2019 may be the norm within the lifetime of our children is a sobering thought, one which makes the case for tackling the climate and biodiversity emergency with the urgency it requires very obvious to even the most agnostic citizen.

By Professor John Sweeney

John Sweeney is emeritus professor of geography, Maynooth University and has taught and researched various aspects of climate change in Ireland for over 35 years. Prof Sweeney is also a former member of IPCC panels.

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