In summer 2022, extreme water shortages and heat waves were observed in Europe, North America and China. In particular, France and Germany experienced extremely dry soils, and mainland China experienced extreme temperatures and drought. Insufficient soil moisture could lead to poor harvests and increased wildfire risks, and in addition to already high food prices, is expected to threaten global food security.

World Weather Attribution, which analyzes the cause-and-effect relationship between extreme events and climate change, assessed the extent to which anthropogenic climate change affects the probability and intensity of soil moisture loss at the surface and in the root zones of many crops in West-Central Europe and the Northern Hemisphere extratropics.

The results of the soil surface model analysis indicated that low summer surface and root zone soil moisture conditions such as those observed in 2022 could occur once every 20 years under today's climate conditions, but would have had a much lower probability of occurring in the early 20th century, and that anthropogenic climate change has likely increased the probability of causing soil drying conditions.

A summary of the main findings indicates that in West-Central Europe, anthropogenic climate change may have increased the 2022 root zone soil moisture drought by a factor of 3-4 and the surface soil moisture drought by a factor of 5-6.

For the Northern Hemisphere extratropics, the impact of anthropogenic climate change on soil moisture drought was estimated to be much larger, at least 20-fold in the root zone soil moisture and 5-fold in the surface soil moisture. However, these indicators are difficult to observe quantitatively in practice, and the exact numbers are uncertain.

The model further indicates that the frequency of soil moisture droughts increases with global warming, which is consistent with the long-term climate model trends reported in the IPCC AR6.

Contributor: IIYAMA Miyuki (Information Program)