4 things you may not know about the heat wave

Scott Weaver

The National Weather Service issued extreme heat warnings for a large swath of central United States this week, drawing comparisons to the dangerous heat events of the Dust Bowl in the 1930s.

The combination of extreme heat and humidity in large Midwestern cities such as St Louis and Chicago will likely lead to a range of human health impacts, including the potential for fatalities. Naturally, some will question whether this heat wave is the result of human-caused climate change.

Here are four things to consider as we sort that out:

1. Temperature is only part of the story

While it is unclear at this time if daily temperature records will be broken during this event, it doesn’t necessarily matter. The dangerous impacts from heat waves occur as a result of both temperature and humidity , especially if these conditions persist for more than two days, as is expected for this event.

We now know that the increase in global mean temperature as the result of greenhouse gas emissions is pushing us into a new climate reality where extreme heat events are much more likely.

As if heat isn’t enough, increasing atmospheric temperature has also boosted global evaporation. This has led to an increase in global atmospheric moisture content over the last several decades, and by extension a propensity for stronger heat indices.

2. Thermometers don’t matter

The metric used to quantify the combined temperature and humidity impacts on humans, the heat index, is what makes a day feel like 110 degrees even if the thermometer only shows 96 degrees – much the same way a wind chill feels colder than the mercury suggests.

With the heat index already above 105 Fahrenheit for two days straight and then rising as high as 115 F  in many Midwestern locales, health officials are urging millions of Americans to stay hydrated and indoors.

3. Day 3 of a heat wave is critical

The third day is also critical for the human body. That’s when people who remain exposed to extreme heat can often no longer cope and fatalities historically rise, especially if temperatures remain high at night and keep people from resting.

With the heat building over the eastern half of the U.S. and expected to last into the weekend, even President Obama weighed in via Twitter this week, urging citizens to “drink water, stay out of the sun and check on your neighbors.”

4. Natural cycles may play a part, as with Dust Bowl 

There are always natural climate cycles at play and they can conspire to temporarily enhance or detract from the continually increasing climate change signal.

These cycles are usually expressed through changes in the surface temperature of the Pacific and Atlantic Oceans and have fancy names such as the Atlantic Multidecadal Oscillation, Pacific Decadal Oscillation and the El Niño Southern Oscillation.

But their impact is really quite simple: Because the Atlantic and Pacific oceans are so large, these natural cycles can heat large areas of the atmosphere from underneath, much like a stove heats a pot of boiling water. When aligned like they are right now, they can contribute to extreme heat and drought in the central part of the country.

The 1930s catastrophic Dust Bowl…originated from a combination of these natural cycles.

It’s happened before. The conditions that kicked off the 1930s catastrophic Dust Bowl in central U.S. are widely reckoned to have originated from a combination of these natural cycles.

To be sure, the events in the 1930s also had a human cause, including poor land management and agricultural practices that led to a large-scale depletion of soil moisture. It warmed the land surface over the Great Plains and Midwest, exacerbating a persistent and large high-pressure system already in place.

Is it climate change? Science will tell.

Of course, our impact on the climate is much different today.

With monthly and annual temperature records being smashed month after month and year after year – recently pushing global atmospheric greenhouse gas concentrations past 400 parts per million – it’s likely that human-caused global warming is playing a large role in this week’s heat wave.

Also different today is that the science of linking climate change to large-scale extreme heat wave events has advanced rapidly over the last decade, helping us know when to attribute extreme weather events to global warming.

So stay tuned as this week’s “heat dome” unfolds. The climate science community will be rolling up their sleeves, once again, and go to work to understand the various forces at play.


To sleep, use ice packs in your bed. This will cool your body temp. During the day, cold bandannas across the back of your neck or around wrists with an ice cube in them will help. Cooling wrists can quickly take down body temp.

Sue Stroud
July 22, 2016 at 4:39 pm

You talk about the impact on"large cities" across the midwest. Are not the small cities also impacted? Don't they matter?

Bette Thomas
July 23, 2016 at 3:37 pm

Hello Bette,
Thank you for the comment. Apologies for what may seem like an oversight. You are correct that small cities are important. I was trying to call attention to the fact that millions upon millions of people were going to be negatively affected by this event. Sometimes when east or west coasters hear the term "Midwest" they only think of the beautiful rural farming areas and I wanted it to be clear just how many of our fellow Americans were going to be affected. Have a great day!


Scott Weaver
July 25, 2016 at 11:35 am

In reply to by Bette Thomas

Oh, thank you very much, you guys do a good job warning us old people in advance. How much water should I drink and what food should I eat? Can I exercise at the health club?
Thank you,
Walter Rossi

walter rossi
July 23, 2016 at 3:49 pm

The heat wave you are talking about might be related to global warming, because I have seen winters getting milder with less snow in Northern Virginia, and I have noticed that snow fall has disappeared around year 2005. I can recall getting a few inches of snow on Christmas before year 2005 every year, but not after 2005.

Human civilization plays a Russian roulette with the biosphere of Earth, because around 2,000 years ago, an ancient Roman traveler writes how he rode for two weeks on his horse from Spain to what is today Poland without seeing the Sun, because European forests were so vast and dense, and full of many wild animals.

So far, 99% of iconic huge trees (the size of California red woods on the West coast) on the East coast have been put to axe, and just think about what many species have gone extinct. Huge and old trees provide shelter and shade for animals and people. Large trees are like natural A/C units, because the trees store water (which cool from hot air) and provide shade at the same time.

There are too many people having too many children, and more than 7 billion people need more roads, towns, cities, schools, factories, parking lots and so forth at the cost of turning the sphere into a commodity. There is a need to slowly reduce human global population from 7 billion to 2 billion (and keep it at 2 billion for next 10,000 years).

Piotr Sliwka
July 23, 2016 at 4:21 pm

Thank you Piotr Sliwka for speaking out and telling it like it is. What you said was spot on. I'm so glad there are other people who have common sense and can tell the world the honest truth about how the human race is a big part of all the problems we are having with climate change. Thank you for pointing out to other people the reality of our environmental crisis.

Loretta Thompson
July 26, 2016 at 4:48 pm

In reply to by Piotr Sliwka

Very helpful article. Thanks for posting.

Dick Clark
July 23, 2016 at 4:22 pm

Hi Scott,

Great article, scientific, well-balanced and factual without any hyperbole. Hard to get these days on such a polarizing issue.

Gary McCray
July 23, 2016 at 4:32 pm


Thank you for reading my post. What you describe is exactly what I strive for on a daily basis. Thank you for noticing.


Scott Weaver
July 25, 2016 at 11:43 am

In reply to by Gary McCray

I'm fortunate, I can generally take the heat better than some. I pour concrete in all weather. I do feel for the elderly and others.

Jeremy Wales
July 23, 2016 at 4:38 pm

Do you think Styrofoam snowballs will be thrown in Congress as Republicans continue to deny climate change? Will this extreme heat wave finally make them deal with reality? Buy the way, Styrofoam lives in landfills forever.

Gail Landy
July 23, 2016 at 6:29 pm

Hi Gail and thanks for your comment. It was actually a real snowball a Republican senator threw on the floor of Congress! :)

Karin Rives
July 25, 2016 at 10:12 am

In reply to by Gail Landy

This heat wave issue is not only in America. We've felt its impact all over the planet Earth.

July 23, 2016 at 6:45 pm

I wish someone would tell me why most evangelical and fundamentalist religious groups are so dead set against the idea of man-induced climate change. What is their problem?

rod repke
July 23, 2016 at 7:11 pm


Please look up Dr. Katharine Hayhoe, a very respected climate scientist who is also an Evangelical Christian. She speaks often and openly about this topic and has some really important insights that we can all benefit from. She's on Facebook and Twitter. Google her. I think you will be glad you did.


Scott Weaver
July 25, 2016 at 11:41 am

In reply to by rod repke

Fire near Los Angeles is sending smoke everywhere and ashes are falling.

Gerald Orcholski
July 23, 2016 at 7:50 pm

It drives me crazy to hear people deny that global warming is real. I will not be here to experience the long-term effects, but my grandchildren and their grandchildren will. It gives me no pleasure to know that there will come a time when people can no longer deny that the climate has already passed the no-return point, that we were right.

virginia rice-…
July 23, 2016 at 8:03 pm

I am a Democrat -- Lord help us, but they are the best we have now, and I am a believer in human-caused climate change. Of course, I take and read about eight different science magazines starting with Scientific American and continuing on from there. I have put my money where my beliefs are by purchasing solar panels for my California roof, $40,000 worth.

Unfortunately, I am a 75-year-old lady and as such, you know, "I know nothing." I really don't understand why it is believed that one could live and read for 75 years and still know nothing.

Mary R Mcdermith
July 23, 2016 at 9:08 pm

These recent chain of events with high temperatures in the United States and globally should make the perfect weapon in our defense to aim towards politicians [in Congress] who are denying greenhouse gases as the main reason for global climate change. This summer is an eye opener for a lot of people (even if it is part of El Niño Southern Oscillation).

Ianmichael Richards
July 24, 2016 at 7:53 pm

Perhaps the balance of nature is affected by the swirling plastics floating in the oceans. Why is there very little info for the public about what is being done about that? Mostly we hear scare tactics.

How about movement on what can harm fish and environment? Years ago menopausal symptoms were targeted by drug companies. What happened to all the hormones people stopped ingesting? Did they end up in our water systems and cause hormonal changes in our children and aquatic creatures?

Karen David
July 25, 2016 at 8:23 am

The past five years have seen record high temperatures – not only in the United States, but also in others places around the world. Those who deny this man-made global warming do a disservice to the human race and preclude the possibilities of making the changes we need to ensure a decent future.

Nick Way
July 25, 2016 at 10:42 am

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