If global temperatures rise 3 degrees Celsius (5,4 degrees Fahrenheit) above pre-industrial levels before cities can adequately upgrade existing cooling systems, heat-related deaths in the United States are expected to increase fivefold each year, according to a new study. This trend could decrease by 28% if cities, particularly in northern states, have increased access to regulated environments and become more heat tolerant.
According to a study published this week in the journal GeoHealth, much of the increase in the number of deaths from heat and cold is due to population growth and the increasing proportion of people aged 75 and over. According to the researchers, the elderly are ten times more sensitive to heat and cold than young adults, and therefore, as the US population ages, a larger proportion of citizens will be at risk.
Until the 3 degree threshold is exceeded, the effects of climate change alone do not significantly affect the overall number of deaths from temperature-related health effects in the United States.
“We found that in the future, the increase in heat-related deaths will mostly affect the northern United States,” said Jangho Lee, a climate scientist at the University of Illinois and lead author of the study. This is because southern cities like Phoenix or Houston are much better adapted to the heat than those in the north.
Warmer winters reduce deaths from cold, but lives saved strike a balance with increased deaths from heat. According to the study, this balance will last until global temperature averages reach 3 degrees Celsius, at which point temperature-related deaths will begin to increase rapidly.
If current carbon emissions are not controlled, this temperature exceedance point could be reached by the end of the century.
“Because cold kills more people than heat in the United States, some people argue that climate change will save more lives,” said Andrew Dessler, a climate scientist at Texas A&M University and one of the study's authors. But that's not what we discovered. Unfortunately it won't save many lives. Up to roughly 3 degrees of warming, there will actually be devastation in the United States. After that, it depends on your level of adaptation.
The study used data from 1987 US cities between 2000 and 106, that is, about 65% of the country's population, and found that an average of 36.444 deaths per year were due to heat: 4.819 deaths were due to heat and 31.625 deaths (85%) were due to cold. Only 5% of the population was over 75 years of age during the study period, making up about 75% of those who died from heat or cold.
According to the study, with the global average warming of 3 degrees Celsius, the combination of a warmer environment and an older, growing population will result in 200.000 annual deaths from heat-related causes in these cities. This number could be significantly reduced to 144.000 by aligning all cities in the United States with those most prone to heat impacts.
Surprisingly, most cold deaths occur well above freezing and only 22 degrees Celsius (72 degrees Fahrenheit) below the optimum temperature of 5 degrees Celsius (9 degrees Fahrenheit) in most places. In contrast, high-temperature-related deaths are more closely linked to temperature rise.
According to the research, the greatest number of lives would be saved by reducing exposure to moderately cold conditions.
In southern cities, where a high percentage of citizens already have access to some air conditioning, the extreme temperatures that caused the biggest increase in deaths were predicted to have little impact. The result is a heavy loss of life pushed northward.
Among the cities included in the study, Minneapolis, Milwaukee, and Muskegon, Michigan are expected to see the largest temperature changes (0,96, 0,88 and 0,86 degrees above the world average, respectively).
We cannot accurately predict people's future adaptation. We don't know how the laws will change and how much money we will spend. That's why we developed two scenarios that limit adaptation, says Lee, one of whom is full adaptation and the other is no adaptation at all. According to Lee, full adaptation means that future hot cities will adopt the cooling infrastructure of places further south that currently experience similar temperature ranges.
Dessler advises against extrapolating to other countries from the situation in the United States, a wealthy nation with arguably the best ability in the world to purchase temperature relief. According to him, cold-related deaths are rare in tropical regions and many countries are already struggling to control current temperatures. These areas will not have any advantage, heat stress will only increase.
📩 08/09/2023 17:11