Nobody credible is denying that there has been global warming, what is very much in contention is the extent and the cause.
I'm not sure why anyone is surprised that there is uncertainty in science. That's the nature of the beast, man.
As for the credibility comment, well I agree that no one credible is denying warming. And no one credible is babbling about a global scientific conspiracy either. Yet, surely you recall that for the entire 1990s this same cabal of "skeptics" were the ones that hollered that
"there was no warming trend". That the warming trend was the invention of lying, liberal scientists who were misinterpreting their data.
It's only been in recent year that these very same "skeptics' have had to move their goal posts, and flip flop to say that there
is warming but that it isn't man made.
They were wrong, horribly wrong in the 1990s. When someone is that wrong, I'm usually not inclined to give them the benefit of the doubt when they holler
"But, THIS time I'll be right!"
Thousands of the world's top climate scientists
who actually do their own peer reviewed research in this area have given us an informed conclusion that there is a high probablliity that the recent warming trends are being exacerbated by human activities.
The skeptics, almost universally, are all either non-scientists, or they don't do any of their own peer reviewed lab or field research in climate science. They don't collect and present their own peer-reviewed data sets. All they do publish articles on blogs, issue statements to the press, or write a non-peer reviewed article for some rightwing think tank. Cranks yelling from the back bench and from the peanut gallery, in essence.
In other words, I disagree with your assertion that the effects of global warming "are very much in contention". They're not. Unless you consider rightwing think tanks, and statements to a blog or a newspaper from some dude to be legitimate science. It's not. The skeptics aren't providing their own legitimate peer reviewed science. They're just complaining, and writing articles for blogs and think tanks. That isn't science, bro.
The fact that there is uncertainty is not a reason to do nothing. Although, scientists have concluded with a relatively high degree of confidence that human activities are significantly contributing to climate change, it's never going to be proven with absolute, bullet proof certainty. But, that's just the nature of science. The question, from a policy perspective, is one of risk management. Risk management is what policy is always about. Indeed, in your every day life, managing risk is done on a daily basis even absent 100%, guaranteed bullet proof certainty of facts. That's just life.
The question is, how high is the probability that humans are influencing the climate (pretty high, according to the world's top climate scientists), and even without ever knowing fully 100% the nature of that risk, how should we manage the risk, or should we even worry about managing the risk.
Changing the climate on a global basis is a pretty huge risk. Even if we aren't fully 120% certain of the exact nature of the risk. Ronald Reagan fucking moved like a bolt of lightening and imposed a hardcore and severe complete worldwide ban on CFCs on the basis of less information, than we have now on greenhouse gases. And you know what? The same denialists who said in the 1990s that there
was no warming were the same denialists who said that CFCs and the Ozone hole were all liberal lies, as well.
Its the same shit, different day, man.