by David Spratt, first published at Safe Climate Australia
The claim that four billion people could die in a 3°C warmer world has become a powerful climate narrative. But what does the science actually support, and where does evidence end and speculation begin?
The proposition that four billion people or more would be dead if — and more likely, when — global warming reaches 3 degrees Celsius (°C) has gained some currency, mainly due to the 4DB (four billion dead) website and associated activities.
Now, that is half the current global population, and on current warming trends of 0.3-0.35°C/decade, the world will hit 3°C around 50 years from now, perhaps earlier, in part because there is little prospect of a rapid decline in fossil fuel emissions. So that’s a mind-blowing average of 80 million people a year dying due to climate impacts every year from now to 2075? Is that realistic?
The number of greater than four billion dead at 3°C first appeared in a 2025 report on Planetary Insolvency: Finding our balance with nature, published by the UK Institute and Faculty of Actuaries (IFoA) and the University of Exeter.ing our balance with nature, published by the UK Institute and Faculty of Actuaries and the University of Exeter.
