>>Why DO Christians, particularly evangelicals, hold completely irrational beliefs...

It might have to do with another IMO even more irrational belief. If you know any Evangelicals, ask them about "The Rapture". Failing that, try to read one of the books in the "Left Behind" series. They're pretty terrible, cardboard cutout characters in unrealistic situations, so just use it to see what they think is going to happen - and what they hope will happen to us 'unbelievers'. IMO it's more revenge porn than anything else - but that's their worldview.

Now, if they believe that that's what's going to happen, why would they care about global warming.