Also there's a great middle-school age text about envirnomental issues called," Facts, not Fear". Its put out by Regnery publishing, written by Micheal Sanera and Jane Shaw, and covers all the so-called envirnomental crises.
It uses real facts and economics to counter each of the so-called environmental crises. I have my middle-schoolers read it for science in our homeschool- it's excellent.
If you can't project the weather "FOR THE ENTIRE WORLD" with certainty for a week, you can't project it for the next 20 years. It's simply one of those uncertainties.