Extreme Heat Risk (IPCC CMIP6)

Source: IPCC CMIP6 Year: 2050 Category: Physical risks · Mitigating services · Climate Acute Risks Coverage: Global Format: Raster grid (~25 km) Used in risk analysis: Yes — gates Mitigating services

What it shows

This layer measures exposure to extreme heat under a forward-looking climate scenario. It indicates how often very hot days are expected to occur, which matters for human health and productivity, agriculture and livestock, cooling-energy demand and the stability of infrastructure at and around a site.

How it is built

The layer draws on IPCC climate projections from the CMIP6 model ensemble. It reports the projected annual number of days with a maximum temperature above 35 degrees Celsius under the SSP2-4.5 scenario, which corresponds to roughly +2 degrees of global warming — the Paris Agreement target. To reduce the influence of any single model, the value at each location is the median across 27 climate models.

How to read it

Higher values mean more extreme-heat days per year are projected, indicating greater exposure to heat-related risks. Lower values indicate fewer such days. The measure is a count of hot days, so differences between locations can be read directly as differences in heat exposure.

Class thresholds

The underlying layer models a physical flux: the projected number of days per year with a maximum temperature above 35 °C (days/year), taken as the median across 27 CMIP6 models under SSP2-4.5 (~+2 °C warming). It is a continuous raster, not a five-class product: the colour ramp runs over the full range from 0 to 100 days/year rather than along fixed risk bins, so there are no class breakpoints — higher pixel values simply mean more extreme-heat days.

A site is flagged on the Mitigating services dimension (local climate regulation) when the layer value exceeds 30 days/year above 35 °C.

How these thresholds were set. The day-count quantity comes straight from the IPCC CMIP6 projections; there is no published class scheme to follow. The single 30 days/year flag cut-off is a Darwin in-house screening threshold (a round-number cut on the modelled day count), not an IPCC or WWF standard.

Reference: IPCC Interactive Atlas — interactive-atlas.ipcc.ch.

Source

IPCC Interactive Atlas — CMIP6 model ensemble (SSP2-4.5, +2°C warming level). https://interactive-atlas.ipcc.ch/.

Comparison with the WWF Risk Filter Suite

This maps to WWF Biodiversity Risk Filter indicator S3_5 Extreme Heat. WWF builds its extreme-heat indicator from a GFDRR wet-bulb-globe-temperature dataset, whereas Darwin uses IPCC CMIP6 climate projections. The hazard is the same, but the underlying source differs.

Risk analysis

A site is flagged on a dimension by combining a proximity trigger (this layer) with an activity trigger (the entity's ENCORE pressure/service). Proximity only → Potentially material; proximity and the matching ENCORE pressure/service is material → Very material; neither → Not material.

Legend

Symbolised field: Days with TX > 35°C

Generated from darwin/layers/layer-extreme-heat-risk-ipcc-cmip6.toml and risk_indicator_pairs.toml (develop).