Internal variability in European summer temperatures at 1.5°C and 2°C of global warming

Description

The aim of the Paris Agreement is to limit global warming at 2°C with respect to preindustrial conditions, preferably at 1.5°C. The research study found out that the global difference of 0.5°C on an annual basis will not result in 0.5°C difference in European summer temperatures, but the difference will be larger. Compared with 1.5°C global warming, 2°C of global warming will lead to around 1°C higher summer monthly mean temperatures over Europe. On a daily basis, the differences in extreme temperatures will probably be even larger.

At 2°C global warming extreme maximum daily temperatures can be reached that are up to 1.5°C higher than maximum temperatures at 1.5°C global warming, according to a recent model study on summer temperature variability at these levels of global warming. This is due to the fact that the variability in summer temperatures is higher at 2°C global warming compared with 1.5°C. As a result, the 10% most extreme summer maximum temperatures in a 2°C warmer world cannot be reached when global warming is restricted at 1.5°C. 10% may not seem that much, but these events would correspond to the most extreme and severe heat waves, the ones with the most critical consequences.

These findings show that the amplitude of extreme temperature events cannot be controlled in the future by establishing global mean temperature limits. When the impacts of climate change are evaluated, the range of temperature extremes that results from climate variability should also be considered.

Typical European summers at a global warming level of 1.5°C are the hot summers of 2003 and 2017. The 2003 summer temperatures in Europe will be commonplace around the 2040s. Summer temperatures in Europe in 2010 were more extreme: these values are comparable to the average summer month in a 2°C warmer world. Under the 2°C global warming, every other European summer month would be warmer than the warmest summer month on record in current climate conditions.

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