The World May Have Less Time Than It Thinks to Act on Climate Change

The summer in southern England brought exceptional heatwaves, record-breaking dry spells and consequences that reached well beyond uncomfortable weather. Railway tracks buckled, transport was disrupted and crop yields fell sharply. Farmers warned that food shortages could follow next year.

The familiar climate forecast of warmer, wetter winters and hotter, drier summers does not fully explain what happened. That forecast describes the thermodynamic effect of rising global temperatures caused by greenhouse-gas emissions. A warmer atmosphere holds more water vapour, bringing heavier winter rain when low-pressure systems reach the British Isles. In summer, reduced rainfall and warmer air dry the land further.

But the immediate cause of this summer's drought was a persistent high-pressure system, or anticyclone, that settled over much of Western Europe from late spring. It pushed rain-bearing weather away from the region. The central question is why that anticyclone lasted so long.

One possibility is internal, chaotic climate variability. If that is the explanation, the chance of another similarly persistent anticyclone in 2027 would be relatively small. More typical circulation patterns could return, although the thermodynamic effects of climate change would still make the summer warmer and drier than summers in the 20th century.

The more troubling possibility is that climate change itself made the anticyclone more likely. That would mean warming is changing not only the atmosphere's thermodynamics, but also its dynamics, including the circulation patterns that influence where anticyclones form. The distinction is crucial, the article argues, because altered circulation could make regional climate change advance at a faster and more alarming pace.