Phoenix has always been known for hot summers. But human-caused climate change is driving even more intense heat in the Valley. So how much hotter could future summers get?
The climate research organization Climate Central projects Phoenix’s average summer high temperatures will be 7.2 degrees hotter by the year 2100. That will make the future climate of the Valley feel more like the current climate of Saudi Arabia, Climate Central reports.
And future summers will not only bring more intense highs, but longer heat seasons, said Climate Central climate scientist Zachary Labe.
“We’re going to see summer-like heat extend into the fall and extend into the spring and you might even have a heatwave in winter into the future,” Labe said.
Phoenix’s heat season is already stretching longer. March temperatures this year shattered records in the Valley — Phoenix reached 100 degrees for the first time this year on March 18, the earliest triple-digit day ever recorded in the city.
Fall temperatures in the Valley have gotten hotter, too, with triple-digit heat lasting well into October in recent years.
Since the 1990s, Phoenix has averaged 111 days per year that reach 100 degrees or hotter, according to the National Weather Service. But as the heat season grows longer, those annual totals are increasing. More than 120 days passed the century mark in each of the past three years.
And climate projections show 120 or more days in the triple digits will likely be pretty typical by the 2050s.
Labe said climate models vary. One of the biggest unknowns is how much greenhouse gas humans will keep burning, trapping heat in the atmosphere and warming the planet. But he said even lower-emissions scenarios show Phoenix is on a path to a hotter future.
“Temperature is one of the metrics that we have the most confidence in, whereas things like precipitation it’s a bit more uncertain,” Labe said.
The National Environmental Mapping and Applications Center’s Climate Explorer shows in a lower-emissions scenario, Phoenix may average 124 days above 100 degrees by 2050. But if carbon pollution levels are higher in the future, the Valley could average 134 days a year in the triple digits by 2050, the tool shows.
And, depending on emissions, Phoenix could average 131 to 156 days per year in the triple digits by the 2080s, the Climate Explorer projections show.
“Being that the largest uncertainty is due to humans, that actually, to me, gives us hope,” Labe said. “A lot of these really extreme conditions in the future with more hot weather, some of that can still be avoided depending on decisions we make in the near future.”
Labe said as the planet warms, there will still be natural variability in the climate – not every year will be the hottest on record. But, he said, Arizona leaders should be prepared for a hotter future when making decisions around infrastructure, energy demand, water resources and public health.
“There’s a lot of important planning questions that can hopefully be answered by looking at these climate models,” Labe said.
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