well..
1) it's a fact that co2 is a greenhouse gas
2) it's a fact that we pump out a lot of it into the air
From that we know that there is at least some correlation between increase in greenhouse gasses and increased temperature ( unless there is some negative feedback somewhere else, like cloud formation due to higher temperature, which causes cooling ).
3) as we move off oil in the next 30 years or so the next cheap alternative is coal, processing of which exhaust significantly more co2 and that can make it worse
In my "pulling from my ass estimate" there is maybe 10-20% chance that we will have some major issues due to GW.
I would say it justifies at least some kind of precautionary measures.
investment is nuclear, solar, wind, geothermal, etc sound like a great idea.
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Человек, который почувствовал ветер перемен, должен построить не щит от ветра, а ветряную мельницу