This talk covers two complementary but distinct topics.

First, I discuss projections of temperature variability. While accurate projections of temperature variability are vital for understanding climate change and its impacts, they remain highly uncertain. We use rank-frequency analysis to evaluate the performance of eleven single model initial-condition large ensembles (SMILEs) against observations in the historical period, and use those that best represent historical regional variability to constrain projections of future temperature variability. Constrained projections from the best-performing SMILEs still show large uncertainties in the intensity and the sign of the variability change for large areas of the globe. Our results highlight poorly modelled regions where observed variability is not well represented such as large parts of Australia, South America, and Africa, particularly in their local summer season, highlighting the need for further modelling improvements over crucial regions.

The second part of the talk shifts to the policy space, quantifying the human and environmental consequences of continued fossil fuel extraction. This work links CO₂ emissions from individual projects directly to the additional global warming they cause. Using the Scarborough gas project in Western Australia as a case study, I will show that its emissions would expose an additional 516,000 people globally to temperatures beyond the human climate niche, cause around 484 extra heat-related deaths in Europe by century’s end, and contribute to the loss of roughly 16 million corals on the Great Barrier Reef in each new bleaching event. These findings highlight how climate science can inform decisions that shape Earth’s future and improve accountability for the risks of continued fossil fuel use.