Must be due to Global Warming.
Uh, no, wait - it’s due to Global Cooling.
No, make that Acid Rain.
Er, Overpopulation?
Never mind - give us a huge grant for the next twenty years and we’ll figure it all out for you.
Remember acid rain? We were supposed to have denuded mountains by now here in the northeast.
I think the conclusion that I read somewhere was that land ice is putting more fresh water into the sea, which lowers the salinity, and makes it easier to freeze.
You forgot to mention the ozone hole.
You forgot cow farts.