VIENNA • A population equivalent to that of Germany - 83 million people - could be killed this century because of rising temperatures caused by greenhouse gas emissions, according to a new study that might influence how markets price carbon pollution.
The research from Columbia University's Earth Institute introduces a new metric to help companies and governments assess damage wrought by climate change.
Accounting for the "mortality cost of carbon" could give polluters new reasons to clean up by dramatically raising the cost of emissions.
"Based on the decisions made by individuals, businesses or governments, this tells you how many lives will be lost or saved," said Columbia's Mr Daniel Bressler, whose research was published yesterday in the journal Nature Communications.
"It quantifies the mortality impact of those decisions" by reducing questions down "to a more personal, understandable level".
Adapting models developed by Yale climate economist and Nobel Prize winner William Nordhaus, Mr Bressler calculated the number of direct heat deaths that will be caused by current global warming trajectories.
His calculations do not include the number of people who might die from rising seas, superstorms, crop failures or changing disease patterns affected by atmospheric warming. That means the estimated deaths - which approximates the number of people killed in World War II - could still be a "vast underestimate", he said.
Every 4,434 tonnes of carbon spewed last year into the Earth's atmosphere will kill one person this century, according to the peer-reviewed calculations that see the planet warming 4.1 deg C by 2100.
So far, the planet has warmed about 1.1 deg C, compared with pre-industrial times.
The volume of pollution emitted over the lifetime of three average United States residents is estimated to contribute to the death of another person.
Mr Bressler said the highest mortality rates can be expected in the hottest and poorest regions in Africa, the Middle East and South Asia.
The new metric could significantly affect how economies calculate the so-called social cost of carbon, which US President Joe Biden's administration set at US$51 (S$69) a tonne in February.
That price on pollution, which complements carbon markets like the European Union's Emissions Trading System, helps governments set policy by accounting for future damage.
But the scale revealed by Mr Bressler's research suggests the social cost of carbon should be significantly higher, at about US$258 a tonne, if the world's economies want to reduce deaths caused by global warming.
A higher cost on carbon pollution could immediately induce larger emission cuts which, in turn, could save lives.
Capping global average temperature increase to 2.4 deg C by the end of the century, compared with modest emissions reductions that would warm the planet 3.4 deg C, could save 74 million people from dying of heat.
"People shouldn't take their per-person mortality emissions too personally," said Mr Bressler.
Governments need to mobilise "large-scale policies such as carbon pricing, cap and trade, and investments in low-carbon technologies and energy storage."
Meanwhile, three people were found dead as a massive forest fire burned for a second day in southern Turkey yesterday, the country's disaster agency and agriculture minister said, with efforts to rescue others and extinguish the blaze continuing.
Hot weather and strong winds have caused fires to spread around the town of Manavgat, 75km east of the resort city of Antalya, and nearby villages.