In 2003 and 2004, a pair of studies led by Australian epidemiologist Anthony McMichael tried to calculate the global burden of disease due to climate change. They estimated that climate change was killing at least 455 people every day.

The McMichael studies are the only estimate ever published of the true, present-day burden of climate change on our health. Based on their estimates, by 2025, at least 4 million people have probably died because of climate change, making climate change deadlier than most pandemics and other public health emergencies.

But in the two decades since the McMichael Studies, global warming levels have more than doubled, from 0.6 °C to +1.3 °C, and along the way, climate change has become significantly deadlier. The McMichael studies also used simple approximations, and only looked at a small number of health outcomes, like deaths during heatwaves and floods.

In the last few years, climate scientists developed a new methodology called impact attribution, which uses statistical models and computer simulations to measure the present-day consequences of human-caused climate change. Using these methods, we can trace deaths, disability, and disease back to greenhouse gases, and even specific countries and companies. But getting the full picture of the global burden of climate change is still a massive undertaking.

Our project is an independent working group focused on developing the methodology for a new Global Burden of Climate Change Study, with the ultimate goal to have a comprehensive view by 2030. To do that, we’re connecting climate scientists with epidemiologists whose expertise ranges from heatstroke to hookworms, and working our way through a systematic, comprehensive, and cause-specific inventory of deaths, disease burden, and economic losses.