>
> I've yet to hear anyone from that
> particular lobby address the fact
> that it is still over 2 degrees colder
> now than it was 5000 years ago.
>
i have.
On the energy-industry mailing lists that i've gotten myself on to, there are an amazing number of intelligent, apparently-reasonable, rational people who disagree with the premise that the current warming trend is human-made.
Nobody, when shown the data, can dispute that Global Warming is occurring (globally, 9 of the warmest years on record took place in the last 10... though when they say "on record"... those records only go back 130 years or so). What *is* in dispute is whether humankind has anything to do with this warming.
And that's not so cut and dry.
At many points in the recent past (and i use recent to mean, say, the past 100,000 years) we can show from geological evidence that the planet went through phases of being even warmer that it's been over the past 20 years. So, say the sceptics, this warming cycle has "natural" precedent; why do we need to blame innocent old industry?
There are problems with this argument (i.e. the rate of global temperature change appears to be greater this time than any previous), but essentially it makes logical sense - there is no evidence that human gas emissions are the *cause* of this recent rise, so it *could* be whatever natural cycle it was that caused previous warmings acting independent of humanity.
The simple counter-argument, however, is not a scientific one, but a 'risk-management' one. Sure, this warming *may* not be the result of human activity. But we know that theoretically it *could* be, given that fossil fuel emissions contain gasses that would tend to have a warming effect, if released in sufficient concentrations.
Given the catastrophic social and environmental effects which could be wrought by runaway global warming, it makes sense to act as though human emissions *are* the cause despite the absence of direct evidence. Whatever factors are contributing to this potential global disaster; we only have control over one of them, and the risk is too great to simply ignore.
That's why it's important to realise that there are indeed rational arguments to be made in favour of the theory that global warming is not being objectively *caused* by humanity. However, i do not believe there is a rational case to be made for acting in any way other than to assume that we *are* the cause, from a species-survival, risk-management viewpoint.
In fact, the only arguments *against* making such an assumption are economic. That eceonomic arguments are being listened to, ahead of species-survival ones is the great disgusting irony of this debate.
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