I think the article addresses this fairly well. In addition to shade, evaporation from open water and plant leaves contributes, as does the soil acting as a heat sink.
Botanical gardens are only slightly more effective than trees over roadways from their study, so shade is likely the strongest factor, but the others clearly play a part- from cooling down enough overnight compared to roadways and cement to the evaporation from the denser vegetation having a stronger effect.
The thing that I missed was how such a garden compared to an open, grass park. The difference in vegetation density would be clearer, I think, and might better explain the difference measured between trees over roads and gardens.
From an energy perspective it makes sense, since at least some of the solar energy hitting tree leaves is used for photosynthesis, and reducing Carbon out of its oxydized state. So it's not just accumulated/reflected like for pavement.
Interesting how easy it is to mitigate 5C - and yet we think the world is going to end if temps increase another 2C - when we are basically in an Ice Age and the Earth has only been cooler for brief periods of time in the last 500M years: https://www.climate.gov/news-features/climate-qa/whats-hotte...
Luckily, fossil fuels are going to get phazed out massively over the next 50 years strictly due to economics.
The increase in temperature is just one of the issues. It has probably been mainly publicized as it's an easy "key performance indicator" to get the point across/that can be succinctly referred to. Sea level rise, ocean acidification, global weather pattern shifts, etc. are all also major problems.
Botanical gardens are only slightly more effective than trees over roadways from their study, so shade is likely the strongest factor, but the others clearly play a part- from cooling down enough overnight compared to roadways and cement to the evaporation from the denser vegetation having a stronger effect.
The thing that I missed was how such a garden compared to an open, grass park. The difference in vegetation density would be clearer, I think, and might better explain the difference measured between trees over roads and gardens.