LA heat

Dear Sara,

I would like to read your prediction of the effects of climate change on the traditional four weather seasons.

From a lifestyle preference, it has been nice for me to know that in the summer, there will be the warmth of the ocean. In the fall, we see the shedding of the leaves and the beauty of the trees when they’re bare. In the winter, there may be snow or outdoor sports. In the spring, we see the wonderful flower gardens that people have planted – and the beauty of that can be predicted.

I ask the question because I have some suspicion that that’s going to change in some way, shape, or form. And I don’t look forward to that.

– Claude in Durham, North Carolina

Dear Claude,

Now that summer is upon us, I’m returning to your letter. As you’ll recall, there’s so much I can say in reply to your question that I’m breaking my answer into four parts – one for each season.

As I did last spring, to illustrate how climate change is affecting the season, I’ll be revising the music of Italian baroque composer Antonio Vivaldi.

Here is the first movement of “Summer,” the second concerto from Vivaldi’s famous composition known as “The Four Seasons.” It’s performed here by the Wichita State University Chamber Players, with John Harrison as the violin soloist.

Vivaldi’s music evokes sluggish periods of hot weather interrupted by frenzied thunderstorms, both staples of temperate-region summers. Imagine that his original work represents summer without the influence of human-caused climate change. Now, I’ll change the piece to show you how summers are subtly changing as a result of climate change – with potential consequences for your health.

Broiling, steamy weather

As the globe warms, summers are growing hotter. Humidity is also rising in many U.S. cities.

That doesn’t just leave us sweating more. Changes to humidity and average temperature patterns are redistributing the energy that drives summer weather, Charles Gertler said in an interview with YCC. Gertler is a graduate student at MIT and the lead author of a recent paper on the influence of climate change on summer weather in the northern hemisphere’s mid-latitudes, home to much of the U.S.

He found that compared to 40 years ago, less energy is available to fuel summer-season extratropical cyclones, massive low-pressure weather systems associated with warm and cold fronts. That could explain a change that scientists had already observed: a decline in the number of strong extratropical systems during summer in the northern hemisphere.

“This is not sexy climate change stuff,” Gertler said by phone. “I say that facetiously, but it’s not the very headline-grabbing, extreme event, climate change stuff. It’s not hurricanes, it’s not sea-level rise and storm surge or ice-sheet collapse.”

But, he said, “It’s a change in our just daily experience of weather in the summer.”

And the consequences could be significant. With fewer strong extratropical cyclones, weather patterns may linger longer in the same place, increasing the odds of long-lasting, dangerous heat waves. The changing conditions may also enable air pollution to build up in cities.

Gertler isn’t alone in investigating stagnant summer weather, and the mechanism behind changes to the season’s weather is an area of active research. Several recent studies, for example, have linked climate change to summertime disturbances in the jet stream, a fast-moving river of air that encircles the globe. Those disturbances may contribute to weather patterns to getting “stuck” in place, causing extreme heat waves and floods in some regions.

With that in mind, let’s revisit the opening seconds of Vivaldi’s “Summer.” The music depicts a shepherd and his flocks languishing under the heat of a blazing sun.

To represent a lingering weather pattern, here’s a digitally slowed version of the music.

In this version, the individual notes haven’t changed, but they take longer to pass. Now, the shepherd and his flock must spend more time suffering in the heat.

Stronger storms, drenching downpours

Even as extratropical cyclones have weakened, another weather process – known as convection – has intensified, Gertler said. More energy than in previous decades is available to feed convection, the process of rising warm air and sinking cold air that helps form some thunderstorms. The upshot: “Climate change can lead to conditions that favor more energetic and powerful thunderstorms,” he said.

Near the end of the first movement of “Summer,” a strong wind rises, according to a poem Vivaldi inserted in his score. As a storm builds overhead, the shepherd weeps. It sounds like this:

It’s a strong storm, but not severe enough for our revised version of “Summer.” With climate change pushing the needle toward stronger thunderstorms, we’ll need the rain from this storm to pelt down even more fiercely. Let’s borrow an intense storm – also written by Vivaldi – from a later section of “Summer.” It sounds like this:

Putting it all together, here’s what a climate-changed version of Vivaldi’s first movement of “Summer” sounds like. It’s still summer, and still beautiful, but with extended heat waves and severe storms, the experience is inarguably different.

How to protect yourself

Climate change is altering summer weather in ways that could be harmful to your health.

High heat – especially when coupled with high humidity – can cause heat stress, heat exhaustion, and heat stroke. Athletes, outdoor workers, and those with no access to air conditioning are at special risk of falling ill during heat waves. Temperature spikes can also worsen certain health conditions, such as heart disease and diabetes. And they can be particularly dangerous for children and those over 65.

Because heat waves are growing more common, it’s more important than ever to monitor the weather forecast and take steps to stay cool. This government website offers tips on protecting yourself, family, and neighbors.

Keep in mind that stagnant weather may also lead to worsened air pollution in your area. You can check your local air quality at this website. And here is the CDC’s guidance on protecting yourself during periods of poor air quality.

With an increased risk of severe storms comes a rising risk of flash flooding, so stay alert during thunderstorms. Do not attempt to walk or drive through flood water. Rushing water can knock you over or sweep away your vehicle. For more tips, visit www.ready.gov.


Wondering how climate change could affect you or your loved ones? Send your questions to sara@yaleclimateconnections.org. Questions may be edited for length and clarity.

Explore the “Ask Sara” archive.

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