The report, compiled by the Climate Impact Lab and co‑authored by Professor Michael Greenstone, draws on the average output of 14 climate models to forecast a temperature surge of about 4 °C above the current average by November of next year.
Based on that temperature trajectory, the authors project that 2027 will surpass all previous years as the hottest on record, a milestone that would mark a dramatic acceleration of climate change impacts.
Greenstone highlighted the human toll of such warming, noting that the estimate of 451,000 deaths represents “parents and children, grandparents and neighbours, people going to work, caring for families, and living their lives.” He warned that the figure is “numbing” but underscores the scale of the crisis.
The scientists also warned that if today’s extreme temperatures become the new normal, the world could find itself in a “constant state of emergency” within two decades, stressing the urgency of mobilising tools to protect lives.
According to the authors, the report opens a pathway for policymakers to focus directly on mortality outcomes, arguing that “the most important outcome – which is death – must be at the centre of climate‑action planning.”
The findings arrive as governments worldwide grapple with how to translate climate projections into concrete mitigation and adaptation measures, with the report urging immediate design, deployment, and evaluation of life‑saving interventions.