Extreme events
Wilder rainfall swings make record storms more likely
Open access · cc by · source: Europe PMC
Future record-shattering daily downpours become much more probable because extreme-rain variability grows, not only because the mean inches up.
Study at a glance
- Design
- Computational / modelling — 100-member CESM2-LE analysis of record-shattering daily extremes under SSP3-7.0
- N
- N=100 · 100-member CESM2 large ensemble (other CMIP6 ensembles as checks)
- Population
- Land daily precipitation extremes in CESM2 large-ensemble climate projections
- Outcome
- Record-shattering extreme-rain probability driven by growing variability vs mean shifts
Structured fields used in claim comparison tables when every cited study has a complete layer.
Key findings
Record-shattering 5yRx1d probability rises over most land. In some tropics the late-21st-century probability ratio reaches 15. Variability (σ) changes dominate CESM2-LE in most regions, though other CMIP6 models have more balanced mean and variability terms. A CESM2 event physically resembles the 2021 western European floods, which exceeded a 1000-year return level in observations.
Methodology
Using the 100-member CESM2 large ensemble under SSP3-7.0, the authors tracked 5-year block-maximum daily precipitation (5yRx1d) that beat each member’s own record by at least one 1850–1949 standard deviation, compared that with a stationary climate, and split mean versus variability contributions; other CMIP6 ensembles provided a check.
Limitations
CESM2 has high climate sensitivity and SSP3-7.0 is a high-warming path, so ratios may be upper-end. Extreme-precipitation statistics remain uncertain, observations are short, and tropical mean and variability are still underestimated in models.
How this study connects
Role on claims
Each row is a claim on a concept or method page where this paper supports, challenges, or qualifies the statement. Roles are hand-checked — not a model guess.
This library holds 5 empirical papers on extreme events with measured outcomes rather than reviews.
Evidence for the claim as stated.
Future record-shattering daily downpours become much more probable because extreme-rain variability grows, not only because the mean inches up.
Evidence for the claim as stated.
A 100-member CESM2 large ensemble under SSP3-7.0, checked with other CMIP6 ensembles, finds that record-shattering 5-year block-maximum daily rain (beating each member’s own record by ≥1 1850–1949 standard deviation) becomes more likely over most land. In some tropics the late-21st-century probability ratio reaches 15. Variability (σ) changes dominate CESM2-LE in most regions, while other CMIP6 models split mean and variability more evenly. A CESM2 analogue resembles the 2021 western European floods, which exceeded a 1000-year return level in observations.
Evidence for the claim as stated.
Single-model large ensembles and the CMIP multimodel archive disagree about where uncertainty lives. CESM2-LE attributes most extra record-shattering rain to variability changes; other CMIP6 models are more balanced between mean and σ, and CESM2’s high climate sensitivity plus SSP3-7.0 make the probability ratio of 15 an upper-end figure. The CMIP5/6 extremes paper finds similar regional-mean sensitivity across generations but, at +1.5 °C, larger regional- than global-sensitivity uncertainty. Opening CESM2-LE is not the same as opening CMIP6.
Evidence for the claim as stated.
Large ensembles can separate a change in the mean from a change in variability. In CESM2’s 100-member SSP3-7.0 set, the probability of record-shattering 5-year block-maximum daily rain rises over most land; in some tropics the late-21st-century probability ratio reaches 15, and variability (σ) changes dominate CESM2-LE in most regions while other CMIP6 models split mean and variability more evenly.
Evidence for the claim as stated.
Single-model large ensembles and CMIP multi-model ensembles disagree about where uncertainty lives. CESM2-LE attributes most extra record-shattering rain to variability changes; the CMIP5/6 extremes paper finds similar regional mean sensitivity across generations and, at +1.5 °C, larger regional- than global-sensitivity uncertainty. Which ensemble you open changes whether you emphasise σ or the transient climate response.
Evidence for the claim as stated.
Open questions
Tensions this paper is part of
From concept pages' “where studies disagree.” Disagreement means the same question; scope means different assays, populations, or outcomes.
Single-model large ensembles and the CMIP multimodel archive disagree about where uncertainty lives. CESM2-LE attributes most extra record-shattering rain to variability changes; other CMIP6 models are more balanced between mean and σ, and CESM2’s high climate sensitivity plus SSP3-7.0 make the probability ratio of 15 an upper-end figure. The CMIP5/6 extremes paper finds similar regional-mean sensitivity across generations but, at +1.5 °C, larger regional- than global-sensitivity uncertainty. Opening CESM2-LE is not the same as opening CMIP6.
Single-model large ensembles and CMIP multi-model ensembles disagree about where uncertainty lives. CESM2-LE attributes most extra record-shattering rain to variability changes; the CMIP5/6 extremes paper finds similar regional mean sensitivity across generations and, at +1.5 °C, larger regional- than global-sensitivity uncertainty. Which ensemble you open changes whether you emphasise σ or the transient climate response.
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Same topic cluster — not a recommendation engine.