Health impacts account for about three-quarters of the $224 billion per year total cost difference between the two scenarios. More than one-third of that total is attributed to an increase in heat-related deaths.
To estimate the increased health effects costs, the authors reviewed research detailing extreme heat deaths in 49 American cities that account for about one-third of the U.S. population.
In the high-emissions RCP8.5 scenario, about 9,300 more people in those 49 cities would die each year as a result of increased heat. With adaptation efforts like installing extensive and costly air conditioning, the number of deaths could be limited to 4,300.
In the lower-emissions RCP4.5 scenario, heat-related deaths would increase by about 3,900 per year (5,400 fewer than in RCP8.5), but could be limited to 1,300 with adaptation (3,000 fewer than in RCP8.5).
Those findings raise a thorny question: How to quantify the value and the cost of those lost lives?#^https://www.yaleclimateconnections.org/2019/04/climate-change-could-cost-u-s-economy-billions/