And that's as far as I read. Perhaps cogitator knows something that would give me a greater degree of confidence in this guy. This "only four years left" stuff sounds like more scare-mongering to me.
Call me a sponge. I know a lot of things that scare the h*ll out of me -- things which I know to be very real, yet which if I say them here on FR they are belittled and then besieged with irrelevancy.
The main thing I know is that short-term variability of climate does not change the potential hazards of long-term trends. And that's what Hansen is talking about. Four years to act? Maybe not, but probably important in establishing a framework for actions that will make a difference. The horizon for initiation of these actions is probably a few years further out, but not much.
So no, I don't know "something" that would give you a greater degree of confidence in Hansen. I know a lot of things that if you knew them too, you'd have the same degree of confidence (unfortunately) that I have, which is yes, we don't have a lot of time left before we need to start concerted action. [Note that I think, economically, that we're going to be forced to start acting in ways that benefit the economy and the environment.]
There are several things in this thread that are about the Arctic polar ice cap. I think Gore was a bit bold (for anybody reading, he's predicting the disappearance of the polar ice cap in SUMMER in five years), but I think that every following summer we are going to see a new minimum sea ice extent and volume, or values very close to the minimum, as happened this year.
Here's an article that summarizes the situation fairly well, I think.
Arctic summers ice-free 'by 2013'
(Let's imagine this scenario: in the summer of 2013, the Arctic sea ice minimum extent sets a new record: only 25% of the minimum extent in summer 2007, the current record. I.e., a miniscule remnant of the ice cap survives the summer of 2013. I can hear the conservative skeptics now: "Al Gore was WRONG!!!")
Hunting around, I found this op-ed by science fiction author and editor Ben Bova. I think it's common-sense and I agree with him. I'm certain a large majority of FReepers don't. Oh well.
Ben Bova: It’s best to prepare for the worst on global warming
As a final note: