By 2050, the number of dangerously hot days in this region will more than double. Deadly heat waves are currently rare in the mid-latitudes, but are likely to begin occurring annually in this region. Chicago, for example, is projected to see a 16-fold increase in dangerous heat waves by 2100, the study shows. The situation will be even worse in the tropics, where people could be exposed to dangerous heat most days of the year. Days of “extremely dangerous heat” – defined as 51 C (124 F) – could double. Experts say these heat levels push the limits of human survival. The projections were made on the assumption that average global temperatures will rise by 2 degrees Celsius, an upper limit set in the 2015 Paris Agreement. The agreement says a lower warming target of 1.5 C is preferable, and there is increasing momentum for keep the world to 1.5C by making deeper and faster cuts in greenhouse gas emissions. “Record heat waves of recent summers will become much more common in places like North America and Europe,” lead author Lucas Vargas Zeppetello of Harvard University said in a press release. “For many places near the equator, by 2100 more than half the year will be a challenge to work outside, even if we start to cut emissions.” The study used the heat index, which takes into account both air temperature and humidity to measure the impact of heat on humans. “These standards were originally created for people working indoors in places like boiler rooms – they weren’t seen as conditions that would happen in outdoor, ambient environments. But we’re seeing them now,” said Vargas Zeppetello. The world’s nations agreed at international climate talks in Glasgow, Scotland last year to come to this year’s talks in Egypt with emission reduction plans aligned with the Paris Agreement. Many countries have missed deadlines to submit their updated plans. The study authors said the world needs to find ways to adapt to changing heat levels to avoid an increase in disease, especially among the elderly, those who work outdoors and those with lower incomes. Several European countries are not well prepared to deal with extreme heat. In the UK, for example, few people have air conditioning, trains were canceled and an airport runway melted during a multi-day heatwave where temperatures exceeded 40C for the first time on record. The study looked at predictions from existing global climate models, projections of human population growth and the relationship between economic growth and carbon emissions to determine how much and how fast temperatures were expected to rise. They also estimated that there was only a 0.1% chance of limiting warming to 1.5 degrees Celsius by 2100, and that the world would probably only get close to 2 degrees Celsius by 2050. Many countries and companies aim to achieve net zero — where the greenhouse gas emissions are no greater than those removed from the atmosphere — until the same year. “These are scary scenarios that we still have the ability to prevent,” Vargas Zepetello said. “This study shows you the abyss, but it also shows you that we have some service to prevent these scenarios from happening.”
