Heat and dryness, a deadly cocktail

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As the increase in the concentration of greenhouse gases in the atmosphere warms the Earth, the global temperature increases and, consequently, heat waves increase in duration and intensity. Record temperatures are coming faster and more furiously than researchers anticipated. And that raises questions about what to expect in the future.

That temperatures crossed the threshold much faster than expected could be due to incomplete climate models. In principle, they simulate heat waves and the increase in intensity and probability of large-scale extreme heat quite well. However, on a smaller scale, variations in annual daily maximum temperatures do not follow the same pattern.

The results and observations for certain regions, such as the eastern United States and parts of Asia, allow us to better understand the influence of local factors and the natural variability of the local heat wave pattern. On the other hand, moisture balance, land use changes and soil moisture must be taken into account to obtain more reliable projections of future temperature changes.

More mortality, forest fires and crop failures

It is important to anticipate them because persistent heat waves have serious repercussions on ecosystems and societies. Three in particular stand out: excess mortality, forest fires and crop losses.

The summer of 2022 has been the one with the most deaths in Spain in the past 72 years. No less than 120,000 people lost their lives. In fact, 2022 even surpassed the summer of the pandemic (2020) in deaths. The causes are not yet well understood, but undoubtedly the long, intense and recurrent heat waves have a lot to do with it.

There is no denying that the heat experienced was an all-time high. While on average Spanish summers have had 7 days of heat waves, in 2022 there have been 42. This is the hottest summer recorded in Spain and 31 provinces recorded the highest thermal values high in their history.

Heatstroke

These high temperatures not only kill by the famous “heat stroke”, but also aggravate pre-existing pathologies, such as cardiovascular, respiratory, pulmonary, renal, gastrointestinal or even neurological diseases. In addition, it must be taken into account that a determining factor in this excess mortality is also the collapse of health centres.

Spain tops the records for excess mortality (deaths above the average for a country for a given time) across Europe, followed far behind by Germany and Sweden. The Daily Monitoring System for All-Cause Mortality (MoMo), prepared by the Carlos III Health Institute (ISCIII), estimates that in Spain there have been just over 4,700 deaths related to excessive temperature between late April and early September.

There was, however, a deadly heatstroke across much of Europe, with all-time heat and death records in several countries including the UK. A similar situation was experienced during the austral summer.

Heat and dryness, an explosive mix

If we learned anything from the 2003 drought in Europe, it is that when heat and drought combine, they amplify their respective impacts on natural ecosystems and have devastating effects. That year, the combination generated a major crisis in the primary productivity of forest ecosystems and the death of more than 100,000 Europeans.

Researcher at the Potsdam Institute for Climate Change Impact Research, Efi Rousi and his collaborators have identified Europe as a hotspot for heat waves. The old continent shows upward trends in these extreme events that are three to four times faster than the rest of the mid-latitudes of the northern hemisphere over the past 42 years.

This accelerating trend is related to dynamic atmospheric changes that are primarily associated with an increase in the frequency and persistence of double jet states over Eurasia. The jet stream has a big influence on the climate and determining the climatic regions of the planet and the fact that it splits into two streams is something that science is beginning to understand and estimate its repercussions.

jet stream

Double-jet states are particularly important for Western European heat waves, explaining up to 35% of the temperature variability. Its upward trend can explain much of the acceleration of heat waves in Western Europe, and about 30% of it in the European region as a whole.

Certain configurations of the jet stream are linked to thermal extremes in different mid-latitude regions, key regions for cereal production. This implies that they can endanger global food security and social stability. This research, together with observations related to the Azores High and the drought in Western Europe, advances our ability to assess and anticipate environmental, social and geopolitical risks in the context of unmitigated climate change.

Character font: Fernando Valladares / THE CONVERSATION

Reference article: https://theconversation.com/calor-y-drought-a-cocktail-lethal-191451

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