A new study highlights the increasing threat of extreme soil heat across the globe, shedding light on a problem that has been underestimated in climate change studies. While rising air and water temperatures have been the primary focus, the study emphasises the significance of extreme soil heat and its potential consequences for various ecosystems and human activities.
The research, conducted by a team of scientists from Germany, utilised data from various sources, including meteorological monitoring stations, remote-sensing satellites, data reanalysis sets, and Earth-system models. The TX7d index, capturing the intensity of heat extremes by averaging daily maximum temperatures during the hottest week per year, was used to analyse soil temperatures in the upper 10 centimetres (3.9 inches) and air temperatures up to 2 meters (6.5 feet) above the surface at 118 weather stations across Europe from 1996 to 2021.
The findings reveal a stronger trend in heat extremes within the soil at two-thirds of the sites compared to the air above. Heat extremes in the soil develop much faster than in the air, emphasising the urgency of addressing this issue. Regional variations were observed, with Central Europe, including Germany, Italy, and southern France, experiencing a faster increase in soil heat extremes than near-surface air heat extremes.
The study also highlighted the role of soil moisture in influencing the exchange of heat between soil and air. Human land-use practices, such as deforestation and changes in land cover, play a significant role in impacting soil moisture levels. The researchers emphasised that open habitats like grasslands or agricultural fields may experience faster extreme soil heat due to limited access to soil moisture near the surface.
The implications of soil heat extremes go beyond ecological concerns, potentially contributing to atmospheric warming by releasing extra heat and carbon into the lower atmosphere. The study calls for re-evaluating previous studies that primarily focused on air temperatures and underestimated the impact of soil heat extremes. Understanding and addressing this overlooked aspect of climate change is crucial for developing effective strategies to mitigate its consequences.