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More frequent, co-occurring, and persistent climate extremes in Europe

We investigated changes in climate extremes in Europe for the last seven decades, considering the aggregated changes in cold, heat, drought, and precipitation extremes (Pradhan et al., 2022). For this, we used data on climate indices as measures for climate variability to derive climate extremes. Our investigation is based on 39 climate indices belonging to four climate index groups (i.e., cold, heat, drought, and precipitation). We obtained the data from the European gridded observational (E-OBS) climate indices (version 22.0e) from the Copernicus Climate Change Service (C3S) for the period of 1950 to 2020 [1]. We considered a climate extreme as a climate index value beyond two standard deviations of the mean for the baseline period 1961—1990, accounting for upper and lower ends of severity. In the following, we highlight the key findings. For more detailed results, see Pradhan et al. (2022).

More frequent, co-occurring, and persistent climate extremes

We observed more frequent, co-occurring, and persistent climate extremes in the second than in the first half of our study period (Figure 1). A higher share of locations faces
the upper end of climate extremes than the lower end.

Around half of the study area experienced more frequent, co-occurring, and persistent climate extremes, considering at least two climate index groups. The following sections discuss the three features of climate extremes separately.

Figure 1. Climate extremes are becoming more frequent, co-occurring, and persistent in the second than in the first half of the study period (i.e., 1950–1984 and 1985–2019, respectively) for (a) upper and (b) lower ends of severity. The colour represents the number of climate index groups showing this phenomenon, with the bars showing the share of locations. Source: (Pradhan et al., 2022).

More frequent climate extremes

The second investigated period showed more frequent climate extremes than the first half of our study (Figure 2). Climate extreme frequency has increased for at least two climate index groups for most locations (93%), considering the upper end of severity. These locations are mainly distributed across Eastern Europe and the Mediterranean region.

Changes in extreme climate frequencies vary across climate index groups. For example, fewer locations (<20%) had similar or more extreme “frost days”, “ice days”,

and “heating degree days” in the second half of the study period compared to the first one. This reflected not-so-harsh winters in most locations in recent decades. However, five or more indices had more frequent heat extremes (upper end) for most locations (87%). For example, more than 65% of locations faced similar or more extreme “summer days” and “tropical nights” in the second half of the study period compared to the first one. These findings indicated that heat extremes have become and will become more intense, frequent, and longer-lasting with changing climate.

Figure 2. Climate extremes are becoming more frequent in the second than in the first half of the study period (i.e., 1950–1984 and 1985–2019, respectively) for (a) upper and (b) lower ends of severity. The colour represents the number of climate index groups showing this phenomenon, with the bars showing the share of locations. Source: (Pradhan et al., 2022).

In recent decades, there has been a more frequent drought in Southern Europe and the Middle East. In the second half of the study period, around one-third of our study locations had increased drought extremes (upper end) for at least one index. Similarly, most of our study area (52%) experienced more frequent precipitation extremes (upper end), i.e., for five or more indices.

These locations were distributed across the study area to a lesser extent in the Mediterranean region. However, the increased heavy precipitation was at the expense of light and moderate rainfall. Therefore, the Mediterranean region faced more frequent drier weather conditions.

More co-occuring climate extremes

We observed an increased number of co-occurring climate extremes in the same year and location in the majority of our study area (Figure 3). Between the first and the second half of the study period, the share of locations with co-occurrence of climate extremes (upper end) belonging to three or more climate index groups has increased from 53% to 64%. Mainly, cold, heat, drought, and precipitation extremes have increasingly occurred in the same

year in these locations. In recent decades, parts of Western Europe and the Mediterranean region have become hotspots for climate extreme co-occurrences (Figure 3). In contrast, climate extreme co-occurrences have decreased in parts of Eastern and Northern Europe. There were variations in co-occurrences of climate extremes within a climate index group across our study area.

Figure 3: Climate extremes are becoming more co-occurring in the second (b) than in the first (a) half of the study period (i.e., 1950–1984 and 1985–2019, respectively) for the upper and lower ends of severity. Climate extreme hotspots and coldspots are identified based on the differences in the number of climate index groups between the second and the first half of the study period. Source: (Pradhan et al., 2022).

More persistent climate extremes

In the second half of the study period, climate extremes have also become more persistent compared to the first half (Figure 4). Between these periods, the share of locations with climate extreme persistence (upper end) has almost doubled, considering indices belonging to three or more climate index groups. Spatially, parts of Eastern Europe and the Mediterranean region are hotspots because they have experienced more consecutive climate extremes for different climate index groups in recent decades.

The share of locations with consecutive climate extremes (lower end) has also increased from 20% to 61% between the two periods, considering indices belonging to two or more groups. Parts of Eastern and Northern Europe are hotspots at the lower end in terms of climate extreme persistence. There were variations in climate extreme persistence within a climate index group across our study area.

Figure 4: Climate extremes are becoming more presistent in the second (b) than in the first (a) half of the study period (i.e., 1950–1984 and 1985–2019, respectively) for the upper and lower ends of severity. Climate extreme hotspots and coldspots are identified based on the differences in the number of climate index groups between the second and the first half of the study period. Source: (Pradhan et al., 2022).

References

Pradhan, P. et al. (2022) ‘Climate Extremes are Becoming More Frequent, Co-occurring, and Persistent in Europe’, Anthropocene Science. Springer Nature Singapore, 1(2), pp. 264–277. doi: 10.1007/s44177-022-00022-4.

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