New Scientist: While cities create a warm bubble known as the urban heat island, most farms have an opposite chilling effect. This “cool farms factor” has lessened the effects of global warming across the entire continental US, and could continue to do so, suggests new research. It also suggests projects that plant trees to cool the planet need to be approached with caution. Fields can lower temperatures in two ways: by using solar energy to evaporate water “” in a similar way to a person …