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I totally agree with the sentiment of the article that we must act quickly, though my personal thoughts are that the timeline mentioned in the article is, if anything, longer than we're likely to have. I think it's going to happen much faster. (There's an essay at my personal site detailing my reasons for this. Click on my signature to find it.)
But I also wanted to respond to the sentiment that some have expressed, and that is echoed in the opening graphic, that the problem is not man-made. I think the problem is man-made, but I agree with the suggestion made by the graphic that there are people who are in denial about that. Still, if it turns out it's not, my feeling is that the problem is worse not better. That is, if everything we've done to the planet has had no effect, and it's just getting warmer anyway, then we're giong to need more work, not less, if we're going to have any effect at all to fix things.
The suggestion always seems to be that we should be comforted if the problem is not man-made because perhaps that means man is not responsible to fix it. But the fossil record is littered with the skeletons of long-dead animals who didn't survive such changes, and there's no reason to suppose nature will be kinder to us. So I just don't know why the naysayers are comforted by a belief (whether or not correct) that it's not caused by us. People should be seriously worried about this issue regardless of the cause, and all the moreso if we are not the cause.