Annual mean temperature — 1981-2010 (CHELSA)

Source: CHELSA-CMIP6 v2.1 (Karger et al.) Year: 1981-2010 Category: Physical risks · Mitigating services · Climate Chronic Risks · 1981-2010 Coverage: Global Format: Raster grid (~2 km) Used in risk analysis: No (contextual layer; not used in materiality scoring)

What it shows

This layer maps the average annual air temperature for the 1981–2010 reference period. It provides a baseline picture of the climate that prevailed across recent decades, against which future projections and warming trends can be compared. Temperature is a fundamental driver of where ecosystems, crops and species can persist, so it underpins much nature-related and physical-climate risk screening.

How it is built

The source is the CHELSA high-resolution climatology (version 2.1), one of its standard bioclimatic measures. It describes the mean annual temperature averaged over the 1981–2010 reference window, derived from globally downscaled climate data at roughly a 2 km grid. As a reference climatology, it represents observed historical conditions rather than a forecast.

How to read it

Values are temperatures: higher values mark warmer areas and lower values cooler ones. The layer is best used as a baseline reference to interpret the matching future-projection layer and to understand the climatic envelope of a site.

Class thresholds

The underlying quantity is a physical variable: mean annual air temperature, in degrees Celsius (°C), averaged over the 1981–2010 reference period. This is a continuous-gradient layer with no discrete risk classes — pixel values are the temperature itself, rendered on a smooth colour ramp spanning roughly −20 °C to +30 °C (the display range; the underlying data is not clipped to it). There is no risk-flag threshold: the layer is contextual and is not used in materiality scoring.

How these thresholds were set. There are no class breaks to set — the colour ramp is a Darwin in-house display choice (a linear stretch over the −20 °C to +30 °C range that covers most inhabited land), not a classification. The temperature values themselves come unchanged from the CHELSA-CMIP6 v2.1 bioclimatic climatology.

Source

CHELSA-CMIP6 version 2.1 (Karger et al.), open licence.

Comparison with the WWF Risk Filter Suite

There is no equivalent indicator in the WWF Risk Filter Suite. The WWF Suite publishes present-day risk indicators rather than baseline bioclimatic temperature surfaces, so this is a Darwin reference-climatology layer that supports the chronic-climate theme and the comparison with forward-looking projections.

Legend

Symbolised field: Annual mean temperature

Generated from darwin/layers/layer-chelsa-tmean_annual-historical.toml and risk_indicator_pairs.toml (develop).