This week’s brutal heat is nothing compared to what we’ll see in 45 years, if a new study’s forecast is accurate.
The new report predicts that summers in the Southwest and many other regions of the world have a 90 percent chance of breaking heat records in a given year between 2060 and 2080, if the level of heat-trapping greenhouse gas emissions rises significantly.
But if nations can take measures in the next few decades to clamp down on their carbon-dioxide emissions even moderately, the odds of record-setting heat waves will diminish considerably, the study found.
The emission cutbacks needed would be significant. But they won’t be as stiff as those required to reach the goal of holding down temperature increases to no more than 2.7 degrees F that were set last December by negotiators at the global Paris climate talks, said Flavio Lehnert, one of the study’s three researchers.
Heat-related deaths, more droughts and crop damage could all result if the heat waves are as severe as predicted in the computer models used in this study, the researchers said.
“Recent examples of fatal heat waves and food crises linked to record breaking summer temperatures can therefore serve as case studies for a potential future norm,” said the study, prepared by the federally run National Center for Atmospheric Research in Boulder.
The study went online last week, a few days before two hikers died Sunday in record-setting heat in the Catalina Foothills, while a third person died while walking on the Loop multi-use path on the south side. A fourth hiker who had been missing since Sunday was found dead on Tuesday just off the Ventana Canyon Trail. Two others died that day while hiking in the Phoenix Mountain Preserve and the Superstition Mountains in Phoenix and Pinal County.
Tucson, the Bisbee-Douglas area, Phoenix and Yuma broke temperature records that day with respective readings of 115, 109, 118 and 120 degrees.
But while this heat has been extreme even for June, the hottest month, the new study made ominous predictions for future summers.
Mean summer temperatures in parts of the Southwest will rise by 8 to 9 degrees F by 2060-80, compared to average summertime temperatures from 1920 to 2014, researcher Lehnert said, if greenhouse gas emissions keep rising. Temperature increases would be about half that if the world can achieve moderate emission reductions, Lehnert said.
Looking specifically at the odds of heat records, the study found:
• Globally, the odds of a given summer breaking heat records will rise from about 10 percent today to 80 percent by 2070, if greenhouse-gas emissions keep rising.
• The Southwest and other large parts of North America, and South America, central Europe, Asia and Africa face a 90 percent risk of record-setting summers by 2060-80. That means nearly every summer in those areas will be warmer than the warmest summer from 1920 to 2014.
• The central U.S., Alaska, Scandinavia, Siberia and Australia have a less than 50 percent chance of routine, record-hot summers by then.
• If greenhouse-gas emissions are reduced, the odds of record high temperatures in a given summer, globally, sink to 41 percent. In the Southwest and Far West in general, the odds are reduced to a range of 10 to 70 percent.
• By 2070, 87 percent of the world’s population will live in areas that have at least a 50 percent chance of record-setting summers most years, if greenhouse-gas emissions keep increasing. If they’re moderated, 45 percent of people will be subject to that risk.
The study compared two scenarios of greenhouse-gas emission trends. One assumes emissions will climb steadily, as they had done in recent decades, before leveling off a bit in 2013 and 2014. Human population would grow continuously and energy efficiency improve slowly, meaning demand for electricity and gasoline would stay high.
The other scenario shows greenhouse gas emissions rising very slowly at first and tapering off by about 2060. This would occur with significant increases in renewable energy use and moderate fossil fuel use decreases.
Energy efficiency would increase significantly and some effort would be needed to capture carbon and store it underground.
The new study will be published in an upcoming special issue of the journal Climatic Change, which will detail what researchers conclude are benefits of reducing greenhouse gas emissions. This study’s research was financed by the U.S. National Science Foundation and the Swiss National Science Foundation.
