I don’t envy the IPCC. The International Panel on Climate Change studies looming calamity, and has to talk about it in polite, soft, encouraging tones. Otherwise they’re called “alarmist .” “Unrealistic.” Or (eeeek) “pessimists.”
So we’re facing flooding over coasts where billions of people live , people who won’t be able to farm any more so they and others will starve, people who will move to higher ground where nobody will want them and will try to push them out. We’re facing droughts and floods and freezes and fires due to climate forcing . We’re facing pests and diseases moving into new areas where there’s no resistance to them. We’re facing the triggering of feedback loops like the release of greenhouse gases  from the formerly frozen Arctic and the release of methane  from icy deposits on continental shelves. At that point we can push our puny human contribution down to zero and it won’t matter. The build-up will continue and there will be exactly nothing we can do about it. And that’s only the beginning of what we’re facing. Our grandchildren, your grandchildren, are the ones who’ll find out just what it is that we’ve done.
But God help you if you say that THIS IS A FREAKING DISASTER AND OUR LIVES DEPEND ON DEALING WITH IT.
That would be rude. And depressing. Unless you have something nice to say, don’t say anything at all. If you don’t have a solution, stop being a problem. Oh, and don’t tell us to change anything.
(That’s why it’s also rude to point out the real world evidence: we could be using 100% sustainable renewables by 2050 (pdf) with less dislocation than the Great Recession. Or take it from the IPCC itself . Also a summary of options  in 2011, before recent improvements.)
So the IPCC is doing its best. They’ve said , “Um. I hate to interrupt or anything but, uh, we really, really, really, really, really need to do something. But, ah, if that’s too harsh, you can also tell yourself you’ll try geoengineering.”
There aren’t enough swear words in the English language to do justice to the idiots who want that kind of “optimism.” As I said in one of my many  earlier  posts  on  this  topic , we’ve been so good at controlling planetary processes, our best alternative is to mess with them .