Study in Nature: regional warming has reached 90–94% of 1.5 °C limits

A study led by Francis Zwiers from the Pacific Climate Impacts Consortium at the University of Victoria has calculated that by 2025, regional warming across all 46 IPCC land regions has reached 90–94% of the levels expected at a 1.5 °C global mean temperature increase. According to nature.com, regional warming has also reached 65–76% of the levels projected for a 2 °C world nature.comnature.comnature.comOpen source ↗. While global average temperatures over the past decade were 1.2 °C above pre-industrial levels, attributable regional temperatures in many areas are already statistically indistinguishable from a 1.5 °C climate state.

Bayesian framework and regional differences

To overcome the lack of historical temperature records in data-sparse regions such as Africa, South America, and the polar zones, the researchers combined HadCRUT5 surface observations from 1850 to 2025 with CMIP6 multi-model simulations. The team applied a Bayesian observational-constraint framework known as Kriging for Climate Change (KCC). This method uses climate models as a prior distribution and constrains it with available observations, isolating forced climate responses from internal variability even where early baseline data are sparse.

Attributed warming was found to be highest in northern high-latitude regions, exceeding 2.5 °C. Between 2016 and 2025 relative to the 1850–1900 baseline, the Russian Arctic warmed by 3.3 °C, northeastern North America by 2.6 °C, and northwestern North America by 2.4 °C. In contrast, ocean-buffered areas such as southwestern South America and Southeast Asia warmed by approximately 1 °C, while tropical land regions, including most of Africa, showed temperature increases between 1.1 °C and 1.8 °C.

Anthropogenic drivers and projections

The authors reported that warming across all regions is dominated by greenhouse gas emissions, whose warming effect is 4% to 26% higher than net warming alone nature.comnature.comnature.comOpen source ↗. This thermal effect is partially offset by anthropogenic aerosol cooling. Natural forcing factors did not produce statistically significant temperature trends across most regions, confirming that observed regional changes are almost entirely human-induced. Under a high-emissions SSP5-8.5 scenario, global mean surface warming is projected to exceed 1.5 °C around 2029 and reach 2 °C by 2042.