Precipitation seasonality (CV) — SSP3-7.0 2071-2100 (CHELSA)
This layer projects how unevenly rainfall will be spread across the year late this century, under a high-emissions future.
Source: CHELSA-CMIP6 v2.1 (Karger et al.) Year: 2071-2100 Category: Physical risks · Mitigating services · Climate Chronic Risks · 2071-2100 Coverage: Global Format: Raster grid (~2 km) Used in risk analysis: No (contextual layer; not used in materiality scoring)
What it shows
This layer projects how unevenly rainfall will be spread across the year late this century, under a high-emissions future. It captures the variability between months — whether future precipitation is steady year-round or concentrated in a short wet season. Shifts in seasonality affect drought stress, water-storage needs and the long-term suitability of land for ecosystems and agriculture.
How it is built
The layer comes from CHELSA-CMIP6 v2.1 (Karger et al.) under the SSP3-7.0 scenario for the 2071-2100 period, based on a single climate model (MPI-ESM1-2-HR). The variable is the coefficient of variation of monthly precipitation — a standard measure of month-to-month rainfall fluctuation relative to the average — projected to end of century. It is delivered on a fine global grid of roughly 2 km and, as a single-model projection, is best read as a plausible long-term outlook.
How to read it
Higher values indicate stronger projected seasonality, with rainfall concentrated into part of the year; lower values indicate more evenly distributed rainfall. The layer is most informative when compared against the 1981-2010 baseline variant to reveal how seasonal concentration is expected to change.
Class thresholds
The underlying quantity is the coefficient of variation (CV) of monthly precipitation — a dimensionless bioclimatic measure of month-to-month rainfall fluctuation relative to the average — here projected to the end of the century under the SSP3-7.0 scenario. The layer is rendered as a continuous colour ramp rather than discrete classes, stretched across the value range:
| CV of monthly precipitation | Rendering |
|---|---|
| 0 | Pale (even, year-round rainfall) |
| … | continuous gradient |
| 150 | Dark (strongly seasonal) |
This projection variant carries no risk-flag threshold: it is shipped for visualisation and scenario context and is not used in materiality scoring. The Water-supply risk gate (CV ≥ 68, the global p90) is evaluated only against the 1981-2010 baseline variant.
How these thresholds were set. There are no external class breaks — the layer is the continuous CHELSA-CMIP6 bioclimatic variable on a 0–150 display range. Because this scenario layer is contextual, Darwin applies no quantile cut-off to it; the p90 = 68 threshold that exists on the baseline layer is a Darwin in-house quantile and is not re-applied here.
Source
CHELSA-CMIP6 v2.1 (Karger et al.), SSP3-7.0 2071-2100 projection (MPI-ESM1-2-HR); open licence.
Comparison with the WWF Risk Filter Suite
The WWF Risk Filter Suite publishes present-day indicators and no standalone bioclimatic seasonality projections. This is a forward-looking climate-scenario variant with no distinct WWF equivalent, and is a Darwin extension.
Legend
Symbolised field: Precipitation seasonality (CV)
Generated from darwin/layers/layer-chelsa-precip_seasonality-ssp370.toml and risk_indicator_pairs.toml (develop).