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Comment by obblekk | Hacker News Reader

In the abstract it discusses that most of the effect (16deg Celsius) is from reduced radiative heating and only a few degrees from evaporation.

Mostly the benefit is instead of having the concrete under you absorb and emit the sun, the leaves above you do.

This dramatically reduces the heat we feel at human height.

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> the effect (16deg Celsius)

Did I read that right? 16°C seems like an enormous effect.

Seems like trees would be a small investment to effectively get "outdoor AC-ish"?

EDIT: for those of us who are more comfortable with Freedom Units, that's like going from 104°F to 75°F!

Obligatory response to 'Freedom Units' for those who haven't seen it: https://www.youtube.com/watch?v=JYqfVE-fykk

Yes, and cities with lots of trees are way more livable due to this. Planners in our town seem to hate trees with a passion, thank god we‘re moving away from this concrete desert.

Trees in cities are expensive to maintain, which is why they're often on the chopping block when budgets get tight. This is especially true in places like Las Vegas where there is little natural tree cover due to the climate. You have to have a staff of arborists to keep the trees alive in such a harsh environment.

Indeed, the town I‘m living in was 80% destroyed during WWII and that still shows in its finances. It’s amazing how long major disaster affects a region. Big drug issues, highest cancer rate in the country etc

The problem is that to get these effects you need large canopies of trees, and to get that to happen the trees have to take the space of something else. For street trees it takes away land from parking or traffic lanes; for properties it occupies both horizontal and vertical square footage since the sky above the tree needs to be clear. These are unpopular with some political affiliations and interest groups.

Replacing inefficient street parking and wide roads with trees is a straightforward win.

It is like Sim City 1 where crossroads generated traffic, so you'd replace them with parks.

Even without any evaporative effect, the air cooling of leaves (at least bringing them to the surrounding air temperature) happens more easily than that of concrete pavement due to height and larger surface area. The concrete can easily get heated much hotter than the air at even 10-20ft.

Wrt. water consumption - Mediterranean species like say olive trees are kind of optimized for low water consumption, by for example having leaves covered with wax-like stuff decreasing evaporation.

MIT should deploy their desert water harvesting tech in LV[0]

they just need to figure a way to reorient their panels to provide shade?

[0] only sunlight needed

https://www.thebrighterside.news/post/mits-high-tech-hydroge...

Re: olives, hopefully the terpenes can also help cloud formation

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