As I understand it....
Actually there ARE some pretty simple things ALL nations could do that would significantly address global warming. Two I've read about: FIRST: It would be EASY for each nation to plant 3 trees for every person (in the US, that would be about one billion trees). These would need to be genetically modified and very diverse trees - designed to be very tolerant to disease and changing weather,but this actually is quite doable. If every country did this, the impact would be huge. But of course, every nation won't - especially the two FAST growing contributors to the problem: India and China. SECOND: There is a very inexpensive additive to asphalt that makes it white (well, off white) - thus reflecting rather than absorbing heat. It's very cheap. This sound minor, but cities can easily be 5 to 10 degrees HOTTER than the surrounding area, and this heat radiates into the atmosphere. SOME of this heat is created by machines and A/C but the great majority is because of black roads, parking lots, roofs. We can easily address this, at very little cost. The "tree huggers" keep talking about big, expensive, complex actions that will take years to implement.
But the deforestation in the Amazon may have such a big impact that NOTHING the rest of the world does will matter; there is no way we can plant more trees that are being destroyed there, and the trees we plant in the USA will have less impact that those alone the equator. KEEPING a tree there is simple much more effectual than PLANTING a tree elsewhere.... not to say we shouldn't plant elsewhere, too.
But again, this is just what I've read. I'm no expert.
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