How Shade Can Help Us Survive Our Increasingly Hot Cities

The scorching heatwaves that recently hit Israel, Europe and the United States serve as a warning of what life in an increasingly hotter world has in store for us – not only in terms of actual heat, but of how it affects our daily lives.

As the temperatures soared, it became unthinkable to leave our air-conditioned homes for the outside world, where the sun cruelly blazes, the glare from the ground makes us helpless and the lack of fresh, cool air leaves us panting for breath.

And yet, all these horrific scenarios can be made so much better, with the help of shade. That’s right – not fancy technology, nor ultra-expensive fabrics or gadgets, but plain old shade.

“If you look at the Old City of Jerusalem, or other ancient cities across the Middle East, you’ll see the narrow, winding roads that are so identified with them. These create shade,” Prof. Hadas Saaroni, a climatologist from Tel Aviv University, tells ISRAEL21c.

“And if we look at the rural settlements of the past and traditional Arab construction, we see the flat, white roofs that return the sunlight, and the vines that are grown around them and create shade,” she says.

“Already in ancient times, construction in the hot areas of the Middle East took into account the importance of shade.”

Fast forward a few years, and Israel’s modern cities offer little such respite – think gleaming skyscrapers, black heat-absorbing roads, polluting traffic, the warm air and water drops spat out onto the street by air conditioning, and little to no trees in the urban space.

All these contribute to a phenomenon called urban heat islands, in which urban areas become much hotter than their surroundings, especially at night.

“These urban heat islands are caused by various reasons. First, there are the materials that store heat and emit it only at night. When you add the high levels of humidity at night to the heat, you get a heat load, which in turn leads to people using the AC at night – it’s become impossible not to use the AC at night in Tel Aviv and elsewhere along the coast,” Saaroni explains.

Nighttime AC usage, which has become much more commonplace, is part of the second reason for urban heat islands: human activity, which also includes the heat emitted by cars, restaurants, businesses and industry.

“And finally,” says Saaroni, “there’s the important aspect of vegetation. Plants photosynthesize and lower the temperature around them. And in cities, there are fewer plants. So this combination of little vegetation, heat sources and heat storage all lead to urban heat islands. When there’s no wind, the difference in temperature can also reach 10° C (50.00 °F) at night – that’s very significant.”

Shade, Saaroni argues, can help alleviate life in an urban heat island.

“What I’d like to emphasize, when talking about cities and cultures in the Middle East, is pedestrians,” she notes.

“If we take Los Angeles, for example, or any typical American city, then we can see that it’s geared toward cars. There are no pedestrians. On the other hand, life in a Middle Eastern city, culture in the Middle East, is all about life outdoors, and how people walk from place to place.

“Also nowadays, because of the traffic congestion in the city, people are encouraged to walk as much as possible, and nice, walkable public spaces are required. Walkability is a very important term,” she adds.

“That’s why when we look at pedestrians and people in public spaces, the most important thing is thermal comfort or stress, even more than the actual temperature or humidity. And the most important aspect of thermal comfort in hot areas is undoubtedly the sun’s radiation.”

Nobody needs a scientific study to know that it’s more pleasant in the shade than it is in the sun. But how much shade and what kind of shade is required are questions for researchers.

“We’re not only talking about trees in cities, but also about parks and gardens, and about what kind of shade you put up in these gardens. Take, for example, soft surfaces put in place for young children – if they’re not shaded, kids can get burns on their feet. So it’s all about how you do shade, where you put it and what kind it is – natural or artificial,” says Saaroni.

“There’s still plenty more to be done about this, and we’re realizing it only while in the midst of climate change. The hot season is becoming longer, and the temperatures are intensifying.”

And yet, she notes, records don’t need to be broken for us to feel the heat of climate change.

“Back in 1942, a temperature of 52° C (125.60 °F) was recorded in Beit She’an. Now, it won’t reach 50° C (122.00 °F) in Tel Aviv in summer, and not even more than 40° C (104.00 °F) unless it becomes extreme. But in Tel Aviv, the thermal stress results from the combination of temperature and high humidity. A temperature of 32° C (89.60 °F) combined with 70 percent humidity feels like over 40° C (104.00 °F) in a dry area. The problem here is the high humidity.”

Saaroni has conducted research on humidity and plants.

“In summertime the place with the strongest radiation in the world is Jerusalem, due to a phenomenon called inversion. This radiation combined with lack of shade is unpleasant in terms of temperature.”

“The question posed was whether adding vegetation, in the form of trees and the like, won’t add to humidity levels and therefore hurt thermal comfort levels. My answer was that vegetation contributes more to improving comfort and reducing heat loads compared to the increase in humidity,” she says.

Israel has a few unique elements, Saaroni explains.

“First is that we’re a climate-change hotspot, meaning that we heat up almost twice the average of global warming. Second is what while we are getting warmer, most importantly we’re in an area that has a long hot season which is becoming increasingly longer, with very strong radiation in the hot season that has a strong impact on thermal comfort.

“Also, in terms of radiation, in summertime the place with the strongest radiation in the world is Jerusalem, due to a phenomenon called inversion. This radiation combined with lack of shade is unpleasant in terms of temperature.”

“Research shows very clearly that while we’re going to continue to get warmer, how much warmer is up to us. It very much depends on government and industry policies,” she says.

Saaroni notes that our response to increasing temperatures must include both adaptation to climate change and mitigation of its causes (greenhouse gas emissions) and effects.

“You could say that one solution in terms of adaptation would be to have more AC. That way, I can stay in my AC’d home and go out to malls and air-conditioned commercial centers. But that’s not the point of adaptation, and neither is it mitigation, because if I add ACs I emit more heat into the city.”

Adding more shade is a better solution, she notes.

“The smart thing to do would be to tackle core issues such as shade, or urban forestation, or making roofs white, so that the city will absorb less heat. Aside from that there’s also things such as transferring to solar energy, and establishing green walls. Also, we need to reduce heat sources in the city, for example by reducing parking spaces in cities so that there’ll be less cars.”

In conclusion, says Saari, “It’s very important that we embark on climatic rehabilitation while considering urban heat islands.”

Produced in association with ISRAEL21c