Valuing the Global Mortality Consequences of Climate Change

What is the true human cost of the carbon we emit today?

Tamma Carleton, Michael Greenstone, Solomon Hsiang, Amir Jina, and colleagues at the Climate Impact Lab study the mortality consequences of climate change in their paper "Valuing the Global Mortality Consequences of Climate Change Accounting for Adaptation Costs and Benefits".

They assemble the most comprehensive mortality dataset ever built, covering 40 countries and 38% of the world's population, and use it to project temperature-driven deaths across 24 378 regions through 2100.

Their main conclusions include:

• Both extreme heat and cold raise death rates, with the elderly most exposed. Higher incomes and warmer local climates reduce this sensitivity, as wealthier and hotter places invest more in adaptation.
• Under a high-emissions scenario, climate change is projected to raise the global death rate by roughly 73 per 100 000 a year by 2100, comparable to all cancers or all infectious diseases today.
• Ignoring future income growth and adaptation overstates the projected toll by roughly a factor of three, near 221 per 100 000, close to all cardiovascular deaths worldwide today.
• Poor and hot regions bear the worst: by 2100, climate change is projected to add 140 deaths per 100 000 a year in Accra, Ghana, while milder winters save ~150 lives per 100 000 in Berlin.
• The full mortality risk reaches ~3.2% of global GDP by 2100 under high emissions. The damage is wildly unequal, reaching 27.5% of GDP in Pakistan and 18.5% in Bangladesh.
• One extra ton of carbon dioxide causes mortality damage of about $37, more than ten times prior estimates, but cutting emissions more than halves the projected toll.

This article suggests the carbon prices and damage assumptions in many scenarios are too conservative, which strengthens the case for higher internal carbon prices.

The integrated assessment models behind regulatory social cost of carbon estimates tend to understate mortality damages by up to an order of magnitude compared to this study.

The estimates of how income and local climate soften mortality rely on differences across places rather than experiments, so they are associational rather than strictly causal.

The numbers are also highly sensitive to modelling choices: the study I published about last week found that counting mortality alone could push the social cost of carbon to ~$258, compared to this article's $37.