The extreme heat baking the Southwestern U.S. isn't finished yet. The National Weather Service issued an excessive heat warning today for parts of Southern California and Arizona, including Phoenix, through Monday, saying temperatures are forecast to reach 108-118 degrees each day.
In its alert, the weather service warned of "a major increase in the potential for heat-related illness and even death."
The week has provided a preview of the risks scientists warn are ahead as greenhouse gas emissions continue to raise global temperatures.
Thermometers in the Phoenix area edged up to around 120 degrees for three straight days this week, flights were grounded as the rising temperatures decreased the air density, and the city's main burn treatment center saw twice its usual number of patients with burns caused by walking barefoot on hot pavement or getting into cars that had been heating up in the sun. Several heat-related deaths were reported in the Las Vegas area and in California.
In California, where San Diego County set a record at 124 degrees, some communities faced power outages as air conditioners ran non-stop. Arizona utility APS set a record for power demand, and said it would have been even higher without the recent increase in rooftop solar, which has added more midday power for homes and businesses.
"Heat waves like the one we are seeing in the Southwest are becoming much more frequent," said Robert E. Kopp, director of the Coastal Climate Risk and Resilience Initiative at Rutgers University. "Looking forward, we expect the amount of extreme heat on the planet to continue increasing even more."
Risks to Infrastucture
Since 2000, the world has seen 16 of the 17 hottest years on record.
As the Southwest has experienced this week, rising heat is a risk to human lives and to economies and infrastructure, as well.
"I think we are seeing with the airplanes, for instance, our systems, many of them are built to historical standards, not to standards of the changing climate we live in," Kopp said. "As we push the climate out of the historical realm and into this new realm, we are starting to see some systems break down."
"I think that calls for a major rethink of the systems we rely upon to make sure they stand up to not just in the climate of the past but the climate of the future and also obviously to try to get ourselves into a world that is not quite as extreme as it could be," he said.
Cities are starting to take heat risks and the other impacts of climate change into consideration as they plan new construction. New York City released guidelines this spring to help architects and engineers plan future infrastructure to withstand rising seas, more powerful storms and rising temperatures.
The city expects temperatures to be 4 to 6 degrees higher in New York by the 2050s, adding to heat stress in old buildings with only window air conditioners or no cooling at all. The guidelines encourage architects to design shades over windows, angle buildings to avoid direct sunlight, and use materials and designs that will keep buildings cooler. They also encourage builders to consider power backup systems and air conditioning systems designed for higher temperatures.
Risks to Lives
According to the National Academy of Sciences, the hottest days are now hotter. Since 1950, the number of heat waves has increased across the globe, lasted longer, and covered a wider area. The Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report noted that "most global land areas analyzed have experienced significant warming of both maximum and minimum temperature extremes since about 1950" and concluded that it is "likely that human influence has more than doubled the probability of occurrence of heat waves in some locations."
The EPA also cited a rising risk of deadly heat waves when it issued its endangerment finding in 2009, the determination that greenhouse gas emissions are a danger to human health and ecosystems.
At that point, the planet had already seen the 2003 European heat wave, blamed for more than 30,000 deaths across the continent, and the three-day 1995 Chicago heat wave that killed more than 700 people.
A study released earlier this week estimates that deadly heat waves will become more common across much of the planet. Today, about 30 percent of the world's population is exposed to life-threatening heat waves for at least 20 days a year. By the end of the century, if nothing is done to reduce greenhouse gas emissions, that risk will spread to about 74 percent of all people, the study found.
A new mapping analysis from Climate Impact Lab zooms in for a closer look at how average summer temperatures are expected to rise this century as greenhouse gas concentrations in the atmosphere continue to increase.
With moderate greenhouse gas emissions, along the lines of the Paris climate agreement, the average summer high temperature for the U.S. is expected to rise from a historical average of 74 degrees in the 1986-2005 to an average of 81 by 2100. With high emissions, the lab says we would see an average of 91 degrees in the U.S. Similar scenarios play out across the globe.
The impacts are most damaging in impoverished communities that can't afford air conditioning and have less reliable power. A heat wave that swept across Asia, the Middle East and parts of Europe in late May and early June this year left parts of Pakistan sweltering in 128 degree temperatures, among the highest recorded temperatures worldwide for May.