Sorry Wadadde, my first reply was intended for Ioqi.

To you I say thanks for the effort. The article "What happened to global warming?" is telling in that the reporter feels this comes as a "bit of a surprise" and that those who believe global warming is not necessarily man-made are the "sceptics." I find this paragaph most telling, "They argue that there are natural cycles, over which we have no control, that dictate how warm the planet is. But what is the evidence for this?"

What is the evidence that the earth has heated and cooled all by itself? Serously?

This, I fear, is a good example of how rhetoric is seeping into and trumping science.

"To your first paragraph, "The science is settled" - Al Gore, in a speech to Congress in March, 2007. Al Gore won a Nobel Peace Prize. It was all over the news."

Al Gore is not a scientist, nor is he spokesman for scientists (if there were such a thing).

He is an advocate and an activist. (Not that those are bad things, but he is not a scientific expert and no one would say so, not even him.... I think.)

Al Gore notwithstanding, I don't think the science is ever "settled" with complex phenomena like climate.

There is consensus. But even Newtonian physics turned out to be capable of refinement...

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"I agree that we should notice if our planet is heating up. I also believe we should notice if it's natural or man-made.... What if we manage to wean the world of carbon fuel and it doesn't make one bit of difference? "

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But I think exactly the feeling of most people who believe we should cut back carbon emissions, etc. now before it's too late.

It's that we don't really know, but there's a very strong possibility that man-made impact *will* cause severe, life-threatening climate change in the next century.

We are wagering on this uncertain hypothesis. If we make every attempt to cut back on carbon-emissions, and other human practices that may be impacting the climate of the planet, and we later discover that in fact global warming has been caused by a natural factor... well, what's the problem? In the meantime, we've probably come up with all sorts of new ways to produce energy and better methods at conserving resources. And now that we understand the problem better, perhaps we'll have a fighting chance of doing something about it.

That's if you're right... that climate change is due to natural, not man-made factors.

But if you're wrong, and it's primarily due to man-made factors AND we do nothing about it until we understand climatology better, it may be too late for us to reverse the effects.

So in this wager, isn't it better to err on the side of caution?

I've never really understood why anyone would feel differently...

Okay, the science isn't settled in the sense that as science, it's always open to new data and interpretation. But the science is settled in the sense that not a single scientific body of any nation in the world currently dissents from the prevailing opinion that the Earth has been warming significantly over the past century, and that that warming is significantly attributable to human activity. So in the most meaningful sense, Al Gore was right, the science is very much settled.

Global warming is as certain as any scientific fact can be. We have a century's worth of instrumental records to show the Earth's global mean temperature has been rising. The confidence that this rise is primarily due to human activity cannot be pinned down. The best we have are estimates of consensus among experts in the field. Here's a 2009 survey:

http://tigger.uic.edu/~pdoran/012009_Doran_final.pdf

It says 97% of responding "climatologists who are active publishers on climate change" think "human activity is a significant contributing factor in changing mean global temperatures." In other words, we're pretty damn sure human activity has a net effect of raising the Earth's temperature.

So yes, the science is settled, as much as science is ever settled.