Climate change intensifies extreme heat in the soil. Photo Credit: André Künzelmann (UFZ) |
For a long time, little attention was paid to soil temperatures. In contrast to air temperatures near the surface, hardly any reliable data was available because of the considerably more complex measurement. A research team leaded by the Helmholtz Centre for Environmental Research (UFZ) with participation of Leipzig University has now found not only that soil and air temperatures can differ but also that climate change has a much greater impact on the intensity and frequency of heat extremes in the soil than in the air. According to a study recently published in Nature Climate Change, this is particularly the case in Central Europe.
For the study, the research team coordinated by UFZ remote sensing scientist Dr Almudena García-García collected data from a wide range of sources: data from meteorological measuring stations, remote sensing satellites, the ERA5-Land data reanalysis set, and simulations of Earth system models. The researchers fed these data into the TX7d index, which is defined as the average of the daily maximum temperature in the hottest week of the year. It reflects the intensity of heat extremes (i.e. how high extreme temperatures can be). The researchers thus calculated the index for the 10-cm-thick upper soil layer and for the near-surface air at a height of up to 2 m for the years 1996 to 2021. At two thirds of the 118 meteorological measuring stations evaluated, the trend in heat extremes is stronger in the soil than in the air. “This means that heat extremes develop much faster in the soil than in the air”, García-García, lead author of the study. Based on the data available, this is especially true in Germany, Italy, and southern France. In terms of figures, according to station data, the intensity of heat extremes in Central Europe is increasing 0.7°C/decade faster in the soil than in the air.