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Climate Change and Heatwaves: Are They Connected?

In a word, yes.


The extraordinary heatwave baking the usually cool Pacific Northwestern US this week owned the headlines and caused a lot of media head-scratching, but the bottom line is this:

We’re going to be seeing a lot more heatwaves – and they’re going to be getting hotter and longer – so long as the world keeps burning fossil fuels. It’s that simple.

The Climate – Heat Connection

The science couldn’t be clearer on this one: Burning fossil fuels releases greenhouse gases like carbon dioxide that trap more heat in the atmosphere. More greenhouse gases equals more heat trapped.

And if you missed the headlines, this May, average levels of carbon dioxide in the atmosphere reached the highest level in recorded history. Which means we’re trapping more heat than the Earth can handle. Way, way more.

Over time, this heat has the effect of raising average temperatures across the planet, creating a higher baseline so when heatwaves do hit, they’re even hotter than decades ago. Plus, thanks to all this heat-trapping pollution in the atmosphere, we’ve just lived through the seven hottest years on record. Which means we’re starting from a relatively high floor to begin with – and going up from there.

Source: Center for Disease Control, Climate Change and Extreme Heat: What You Can Do to Prepare

How Unusual Is the Northwest Heatwave? Very.

Simply put, there is no precedent in recent memory for the heatwave hammering the Pacific Northwest, as an epically strong (and hot!) ridge of high pressure settled into the region.

As Climate Reality Director of Science and Solutions Ryan Towell puts it:

“Searching through the area’s long-term records, you’d be hard pressed to find another heatwave that compares in magnitude or duration. Portland, Oregon’s airport recorded its all-time high temperature record on June 26 of 108 degrees only to have that surpassed on June 27 when it spiked to 112 degrees and again on June 28 when the temperatures soared to 116 degrees.

“Seattle’s temperature peaked at 108 degrees on June 28 also setting an all-time high. Under normal circumstances, high temperatures in Portland and Seattle are in the 70s this time of year. Dallesport, Washington appears to have recorded that state’s all-time high temperature of 118 degrees on June 28.

“You might think that just north across the border it’d be cooler, but you’d be wrong. Lytton, British Columbia set a new heat record for Canada when it reached a blistering 121 degrees the next day. Intense heat occurs so infrequently in the region that many lack air conditioning, making this all the more dangerous and unbearable. The good news: the heat dome will be breaking down and shifting east through the week with temperatures easing. The bad news: we can expect to see more frequent extreme heatwaves in the future as our warming planet increases the odds of them occurring.”

Not the Only Heatwave

It’s worth noting that while the Northwest is suffering, it’s part of a larger trend. The week before, much of the American West was racing to set new heat records with many regions above 100 degrees for days on end. Denver, Colorado, for example, had its earliest back-to-back 100 degree days. Tucson, Arizona had multiple days over 110. The list goes on.

Heatwaves and Health

Our bodies work to keep our temperatures at about 98.6°F. When exposed to extreme heat, the body tries to maintain optimal temperature and keep cool by sweating. When humidity enters the picture, sweat is less able to evaporate on our skin and we can’t cool down.

This combination of heat and humidity is together called the heat index – or how temperatures feel to the body - and can make a big difference in turning what sound like hot but reasonable temperatures dangerous and even deadly.

Take a look at the heat index graph below. For example, it may be 96°F (36°C) outside but if the relative humidity is 65 percent, it feels like 121°F to the human body -- while in the shade. Exposure to full sunshine can increase heat index values by up to 15°F. And that’s dangerous. Very dangerous.

Source: Center for Disease Control, Climate Change and Extreme Heat: What You Can Do to Prepare

Heatwaves become especially dangerous when temperatures don’t fall overnight.

As one expert explained, “If the temperature remains elevated overnight, that's when we see the increase in deaths. The body becomes overwhelmed because it doesn't get the respite that it needs… When a person is exposed to heat for a very long time, the first thing that shuts down is the ability to sweat.”

According to the CDC, there are three main phases that the body goes through after prolonged exposure to extreme heat:

  • Heat cramps: “Muscle spasms, often in the abdomen, arms, or calves, caused by a large loss of salt and water in the body. Heat cramps can occur from prolonged exposure to extreme heat combined with dehydration, and they commonly happen while participating in strenuous outdoor activities such as physical labor or sports.”
  • Heat exhaustion: “A severe illness requiring emergency medical treatment. It can occur from exposure to extreme heat over an extended period of time (usually several days), especially when combined with dehydration.” Symptoms include heavy sweating, weakness, nausea or vomiting, and fainting.
  • Heat stroke: “The most serious medical condition caused by extreme heat, requiring emergency treatment. Heat stroke (or hyperthermia) occurs when the body can no longer regulate its temperature, and its temperature rises rapidly—up to 106°F or higher…. It can result in death without immediate medical attention.”

Number of fatalities by hazard (2006-2015) in the US. Source: Center for Disease Control, Climate Change and Extreme Heat: What You Can Do to Prepare

It’s important to remember that, like most climate impacts, heatwaves don’t affect all people the same way. Young children, the elderly, the poor, and people with preexisting conditions (like respiratory disease or diabetes) are the most at risk when exposed to extreme heat.

Key Takeaways

  • Burning fossil fuels releases more heat-trapping greenhouse gases into our atmosphere, resulting in higher and higher overall temperatures across the planet.
  • As more heat energy is trapped in the atmosphere, average temperatures rise and fueling hotter, longer, and more frequent heatwaves.
  • The heatwave baking the Pacific Northwest is without precedent in living memory, with climate change making events like this more frequent and likely.
  • Heatwaves threaten the human body’s ability to safely regulate internal temperature, potentially leading to heat cramp, heat exhaustion, and heat stroke, sometimes with fatal consequences.
  • Heatwaves are particularly dangerous for young children, the elderly, those with pre-existing conditions, and poor families living without air conditioning.

Take Action

While the Western US suffers through record-breaking heat, members of Congress are debating if we need to act on climate at all. The White House has given us a roadmap for aggressive climate action that rebuilds America with clean energy and green jobs and opens the door to a safe and sustainable future for all.

Tell Congress today: We need big and bold climate action – and we need it now.