As greenhouse gas emissions continue to trap heat in the atmosphere, brutal heat waves are becoming more common, average global temperatures are rising, and the lives of millions of people are becoming endangered.
A staggering 18 of the 19 hottest years in recorded history have occurred since 2000, and these records are likely to be surpassed in the decades ahead as the planet continues to heat up.
How much the planet warms, however, has urgent public health ramifications that countries need to consider when addressing climate change, according to a new report published in the journal Science Advances. The report calculates how many additional people will die depending on expected temperature increases.
The researchers looked at what would happen if the planet warmed by 1.5 degrees Celsius, 2 degrees Celsius, and 3 degrees Celsius in 15 different cities in the United States, where existing data on heat wave deaths make predictions possible.
These temperature thresholds were determined by the Paris climate agreement, which urges countries to keep temperatures from rising more than 1.5 degrees Celsius above pre-industrial levels, and says that a 2 degrees Celsius rise is the absolute limit that should be tolerated, after which catastrophic environmental harms are likely to occur.
However, a 3-degree rise by the end of the century is highly likely based on current emissions levels.
The researchers found that hundreds of thousands of additional people will die in major US cities during major heat waves through the end of the century if the planet warms by 3 degrees Celsius.
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“[This research] can be extrapolated to other parts of the world, but we focused on the US because we’re interested in the controversy of the [Trump] administration’s policies,” Eunice Lo, the author of the report and research associate at the University of Bristol, told Global Citizen, referring to the administration’s efforts to dismantle climate regulations. “If we had temperature and health data over a long period of time in a certain place then we could do a similar study in that place.”
“The public health benefits of limiting warming are clear,” she added. “Our hope is that policymakers will realize the benefits to their citizens of cutting greenhouse gas emissions and will increase their climate ambitions.”
By limiting temperature increases to 2 degrees Celsius instead of 3 degrees Celsius, the 15 cities would each avoid between 75 and 1,980 deaths during years with extreme heat waves. Keeping temperatures from going beyond 1.5 degrees Celsius would prevent even more deaths.
The 15 cities included in the study are Atlanta, Boston, Chicago, Dallas, Detroit, Houston, Los Angeles, Miami, New York City, Philadelphia, Phoenix, San Francisco, Seattle, St. Louis, and Washington, DC.
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In New York, an estimated 2,716 lives would be saved per extreme heat wave by keeping global temperatures increases to 1.5 degrees Celsius. Los Angeles, meanwhile, would save an estimated 1,085 in this scenario.
Heat waves primarily affect people who are very young, very old, and sick. The researchers didn’t factor in prospective changes in age across populations, so the actual number of heat-related deaths could be much higher, Lo said. Heat waves also put people at risk of heat cramps, heat exhaustion, and heat strokes, which can all have debilitating side effects.
People living in poverty, who often do not have the same access to air conditioning and cool environments, are also at high risk of heat-related illness and death. People who work in industries like construction and agriculture are also disproportionately harmed by high temperatures because their jobs involve heavy toil outdoors.
Lack of access to air conditioning is common in developing countries around the world and cities often experience blackouts during heat waves because of surges in electricity needs.
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Urban environments are also uniquely susceptible to heat waves.
“Urban people would be exposed to extreme heat more than people in rural areas because of the urban heat island effect,” Lo said. “For the same amount of global warming, urban areas are usually significantly warmer than the surrounding areas because of limited cooling because of tall buildings and construction materials [that trap heat].”
Lo said that the number of deaths would be reduced if cities took action to become more resilient in the face of heat waves.
For example, governments can create parks, rooftop gardens, and plant more trees to cool areas down. Painting roof tops white can also significantly reduce extreme heat events. Investing in public transportation can reduce how many are cars on the road, which can reduce smog-like conditions that trap heat. Finally, cities can make sustainable central cooling more accessible to low-income residents.
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But the best way to stop heat waves, according to Lo, is to curb greenhouse gas emissions.
“The next round of climate pledges within the UN framework takes place in 2020,” she said. “I hope that this research, in addition to previous research that has been done on the effects of mitigating climate change, could really motivate the parties to increase their climate pledges and actions.”