Rainfall is becoming more concentrated in fewer days at many monitored stations

What you need to know

• The study’s measure, called WE50, counts the combined duration of the wettest consecutive precipitation events needed to account for half of annual wet-day precipitation. It describes how rainfall is distributed across time, rather than measuring storm intensity alone. 1
• Across the available station network, half of annual precipitation was typically delivered by about 9.4 consecutive events spanning 27.8 event-days. These are network-wide averages, not a description of rainfall in every region. 1
• Between 1980 and 2022, WE50 declined significantly at 45.7% of stations and increased significantly at 9.8%; 44.5% showed no significant change. The global mean decline was 0.4 days per decade. 1
• The global number of events contributing to WE50 showed no significant change. Mean precipitation contribution per selected event declined globally, so the analysis does not support a general claim that these events are becoming more intense worldwide. 1
• The authors identify uneven gauge coverage and choices about event definitions and concentration measures as limitations. Their analysis of contributing factors is diagnostic, not a direct attribution of the observed changes to a particular cause. 12

Why this matters

A shift in when rainfall falls may be relevant to flood and drought risk, and the study identifies these as potential concerns. But it does not measure resulting impacts on ecosystems or conservation, so the findings should not be treated as evidence of a specific ecological effect. 1

What happens next

Further work is needed to establish how well station-based results represent areas with sparse long-term gauge records, particularly Africa, and to investigate what hydrological or ecological impacts follow from the trends. The supplied reporting does not resolve whether its reference to greater intensity relates to a regional result or a different metric. 13

What we know

• The analysis used daily records from 19,183 rain gauges covering 1980–2022. 1
• WE50 measures the combined duration of the wettest consecutive precipitation events needed to make up half of annual wet-day precipitation. 1
• The reported global mean WE50 decline was 0.4 days per decade, although station-level trends varied. 1
• The global number of contributing events showed no significant change, while their mean precipitation contribution declined. 1

What we don't know

• The analysis does not establish how fully the station network represents regions with limited or unavailable long-term gauge records. Africa was excluded from the study’s continental-scale analysis. 12
• The supplied reporting does not clarify whether its claim about greater intensity refers to a particular region or a rainfall-intensity measure other than the study’s global results. 13
• The study does not measure what hydrological or ecological impacts follow from the observed concentration trends; it identifies these as questions for further research. 1
• The study’s diagnostic analysis does not directly attribute the changes to a specific cause. 1

Read the reporting

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