Dominic Matte, Jens H. Christensen & Tugba Ozturk
Climate Dynamics
Work Package 3
Link: https://doi.org/10.1007/s00382-021-05998-0
Highlights
Extreme rainfall is one of the most damaging climate hazards, and it is expected to increase in frequency and intensity as the climate continues to warm. How extreme rainfall events may change in size, however, is not as well understood. This study addresses this, using an ensemble of climate simulations to look at how the size of these systems might change over Europe at 1°C, 2°C and 3°C of warming. The team found that the spatial extent of areas associated with the most intensive daily rainfall events are set to become larger and more intense, particularly the most intense, core areas of these systems. Smaller systems, however, become less frequent, reflecting a shift towards larger, more intense rainfall systems across Europe. A better understanding of these future changes is a key part of informing future climate policies aimed at limiting the impact of extreme rainfall events and protecting communities and infrastructure.
Background
Heavy rainfall and the flooding it can cause are some of the most damaging climate hazards, with the flooding seen in Europe in the summer of 2021 providing a tragic example. In Europe, extreme rainfall is expected to increase in frequency and intensity as the climate warms, as well as potentially occurring at different times of the year. Comparatively few studies, however, have looked at changes in the size of the geographical area impacted by extreme rainfall events. Different studies on the topic have returned contradictory results. This study attempts to shed light on this issue, investigating changes in the size of extreme rainfall-hit areas at several levels of global warming. Understanding how climate risks could change in the future is a key part of forming effective policies to limit their impact.
Results
The team found that the spatial extent of areas associated with the most intensive daily rainfall events are set to become larger and more intense across the whole of Europe as the climate warms. This effect is more pronounced for the core, most intense areas of these systems. This change could be due to increases in humidity and the overall energy available as a result of climatic warming. At the same time, the simulations show the number of smaller systems falling as the climate warms, showing how larger systems are set to become more dominant and make up a greater proportion of extreme rainfall events. Some differences between European sub-regions can be seen in the results, for instance the British Isles, Iberia and the Mediterranean are set to see somewhat less rainfall from medium-sized systems. A better understanding of how extreme rainfall events may change in future is an important part of forming policies to limit the impact of these damaging events.
Methods
This study makes use of the EURO-CORDEX dataset, consisting of simulations from six regional climate models, driven by five global climate models. 19 climate projections have been produced covering a historical period of 1989 to 2008 to give a comparison with the current climate, then projecting forward from 2006 using the high-emissions RCP8.5 scenario. Rainfall events are assessed at different warming levels within the simulations, when they have reached 1°C, 2°C and 3°C relative to 1986-2005. The heaviest rainfall within the 20-year period when this temperature threshold is reached is used in the comparison, looking at the spatial extent of areas associated with the most intensive daily rainfall events and intensity in comparison to other warming levels.
Policy relevance
The results of this study are useful for informing climate policies aimed at reducing the impact of future climate change. A better understanding of how extreme rainfall events may change is key to putting effective mitigation and adaptation measures in place to protect communities and infrastructure.
Abstract
Using a sub-selection of regional climate models at 0.11° (≈ 12 km) grid resolution from the EURO-CORDEX ensemble, we investigate how the spatial extent of areas associated with the most intensive daily precipitation events changes as a consequence of global warming. We address this by analysing three different warming levels: 1°C, 2°C and 3°C. We find that not only does the intensity of such events increase, but their size will also change as a function of the warming: larger systems becomes more frequent and larger, while systems of lesser extent are reduced in numbers.
Funded by the European Union under Horizon 2020.