The first three weeks of July 2023 have been the warmest global three-week period ever recorded. In the summer months of 2023, twice as many people in Germany were exposed to daily temperatures of 35 degrees Celsius and above the 1980 to 1999 average. This is evident from a recently published study by the Karlsruhe Institute of Technology (KIT). Researchers from KIT’s Center for Disaster Management and Risk Reduction Technology (CEDIM) report that the European population’s exposure to heat was highest in Italy.

In the summer of 2023, several warm spells of varying duration and intensity occurred partly simultaneously in different regions of the Northern Hemisphere. In their “Unterschung der Globalen Hitzwele im Jahr 2023” (Investigation of the global heat wave in 2023), researchers from the Forensic Disaster Analysis (FDA) Task Force Group of CEDIM, KIT, analyzed the reach of the record temperature and the heat exposure of the population. Did.

June 2023 ocean surface temperature warmest since records began

In some areas, previous all-time record temperatures were far exceeded, with other areas setting new daily or monthly records. In June 2023, the global mean ocean surface temperature was higher than ever before. As far as the Earth’s surface including landmass is concerned, June 2023 has been the warmest June since 1850. Globally, the first three weeks of July 2023 were the hottest three weeks ever. According to daily records, the global surface temperature reached 17.08 °C on 6 July, followed by 17.07 °C on 5 and 7 July. In July 2023, Mediterranean countries including North Africa and the Middle East recorded extreme temperatures and new country records – still pending official confirmation by the World Meteorological Organization (WMO) – were reached. Record-breaking temperatures were also reported by the United States, Canada and China.

“For a large temperature anomaly to develop over a long period of time, a long-lasting and unusually large-scale flow pattern is required,” says Dr. Andreas Schaefer of the FDA Task Force Group on CEDIM. The pressure distribution in the middle troposphere at an altitude of about 5.5 km plays an important role, as it affects the upper air flow and the associated air mass transport. “In July 2023, exceptionally persistent high-pressure areas persisted over areas affected by high temperatures. Here, the downwelling air masses contributed significantly to the warming and local development of the heat wave,” says Schaefer.

The researchers also studied the population’s exposure to heat. In Germany, about seven million people were daily exposed to maximum temperatures above 25 °C. These were about 40 percent more than the average number for the years 1980 to 1999. The number of persons exposed to daily temperatures of 35 °C and above doubled to almost 206,000. Compared to previous decades, heat exposure during the summer months was much higher in Italy, Greece, Spain, the US, China and India.

Italy reached a record temperature of over 40°C

Italy faced the worst heat wave ever in Europe. A new record of heat of more than 40 degree Celsius was measured here. While only 4000 people were exposed to such high temperatures per day from 1980 to 1999, this number is expected to increase to more than 127,000 in 2023. To counter the negative effects of heat exposure on human health, state institutions adopted action plans and implemented various adaptation strategies. , which includes the installation of public wells and water distribution systems. In Germany, such systems can be found mostly in the suburbs. (Or)

Original Publication (Open Access)

Andreas Schaefer, Bernhard Mohr, Florian Kaiser, Dennis Bohnke, Susanna Mohr, Michael Kunz: Analysis of a global heat wave in 2023. Report No. 1. CEDIM Forensic Disaster Analysis (FDA) Group, Karlsruhe Institute of Technology (KIT), 2023. DOI: 10.5445/ir/1000161235

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