It’s hot this summer.
Extreme heat is a problem. Plants wilt, especially if there is little rain. Air conditioning costs money and energy. Fires are more likely, road surfaces buckle, power systems fail. People and animals suffer on very hot days, sometimes fatally, and species go extinct.
Every summer is hot in the US, except maybe in Alaska, so it’s hard to tell if this hot day or hot week is different from last year. We need measurements, numbers, to know whether our discomfort is normal or unusual.
Sometimes numbers are misleading. In fact, apparently small changes in average temperature mean big changes in global climate. During the last Ice Age, average temperatures were only 9 degrees colder (in Fahrenheit) than today. The Paris climate agreements are supposed to prevent global average temperatures from rising more than 3.6 degrees from their average before industrialization. Who cares about 3.6 degrees?
Temperature measurements around the world have shown that 2014, 2015, and 2016 were each the warmest years on record. The first half of 2017 is the second-hottest since measurement began. But the differences in average world temperature year to year are seemingly small. The sum of global warming over the past century has been a little more than 2 degrees. These small numbers contribute to the skepticism that many people express about global warming and have allowed the Republican Party to continue its denial about global warming.
Now a new way of looking at our hot summers might help us realize how much global warming affects our lives. James Hansen has put together temperature data to show how our summers have changed over the past 50 years. He classified summer temperatures in the period 1951-1980 into cold, average and hot summers, with about a third of summers in each category. A tiny number of summers were “extremely cold” or “extremely hot”. This range of summer experiences is what we could call normal. There was only about 1 chance in 300 of an extremely hot summer.
The gradual warming of our planet since then has shifted this whole scale toward the hot end. In the period 2005-2015, “cold” summers nearly disappeared. The new normal is a “hot” summer and the number of “extremely hot” summers has multiplied to be about 1 in 7. Now we are in a new decade, and the warming, or maybe hotting, continues. If we don’t do something now, extremely hot will be the new normal.
What is extremely hot? In June, the West suffered the worst heat wave in decades. On June 19, temperatures went over 110 degrees across Arizona and southern California. Temperatures in Phoenix were so high that planes could not fly.
Last week, the Northwest experienced record-setting heat. Portland, Oregon, hit 105 and will set a record for number of consecutive days over 90 degrees, a record set in 2009. Wildfires in the Northwest combined with the heat to make Portland’s air quality worse than Beijing. The Oregon Department of Environmental Quality advised people to limit their time outside to a few hours, bad news for construction workers who can’t do that. Oregon Governor Kate Brown declared a state of emergency.
The heat wave in Europe has been named Lucifer. Across southern Europe temperatures reached over 105 degrees. In Italy, emergency room admissions are up 15%. Wildfires in many countries caused evacuations and road closures. Some regions face droughts.
And people die in heat waves. For example, over 700 people died in Chicago of heat-related causes in 1995, when the temperature reached over 100 for only two days. Heat waves kill more Americans than lightning, floods, hurricanes and tornadoes combined. A team of researchers led by Camilo Mora at the University of Hawaii at Manoa used historic data to determine what conditions make a heat wave deadly. Those conditions will become much more common: for example, New York currently has 2 days a year which qualify as a potentially deadly heat wave, but by 2100 could have 50 such days every year. None of us will be alive in 2100, but do we want to subject our children to 2 weeks of deadly heat waves every year after 2040 or 1 month after 2070?
Global warming is not a model or a prediction or a theory. It is happening to us now, making this summer unbearably hot for millions of Americans in the West. Next summer might be extremely hot in the South or Midwest. If we don’t make it extremely hot for our legislators in Washington, we will condemn our children and grandchildren to unbearable summers every year.
Published in the Jacksonville Journal-Courier, August 8, 2017