Here's a useful little guide to questions about global warming. It's free to download, and it might be useful when arguing with that crazy uncle of yours.
Scientific skepticism is healthy. In fact, science by its very nature is skeptical. Genuine skepticism means considering the full body of evidence before coming to a conclusion. However, when you take a close look at arguments expressing climate ‘skepticism’, what you often observe is cherry picking of pieces of evidence while rejecting any data that don’t fit the desired picture. This isn’t skepticism. It is ignoring facts and the science.
The Scientific Guide to Global Warming Skepticism looks at both the evidence that human activity is causing global warming and the ways that climate ‘skeptic’ arguments can mislead by presenting only small pieces of the puzzle rather than the full picture.
That's a very nice guide to global warming denialism, but I must admit that my own perspective is a little different. I have neither the time nor the inclination to become an expert on climate science. After all, that's why we have scientists. :)
Sure, it's useful to have some familiarity with the arguments, but when push comes to shove, I accept global warming because it's the overwhelming scientific consensus. Simple, isn't it?
This is a scientific issue, and I understand and appreciate the scientific method. So, as with all scientific issues, I accept the consensus of the experts. I'm a layman. I'm not a climatologist myself, and there's no way I'm going to have the education and experience they do in their particular field of expertise.
Really, when it comes to any scientific issue, the only rational move is to accept, at least tentatively - as all science is accepted - the scientific consensus. If you're interested in climate change, by all means study up on it. But the scientific consensus is far likelier to be right than anything else.
And if the consensus is wrong, scientists will be the first to discover that, and the consensus will change. This really isn't a difficult problem, not for us laymen wondering who to believe.
PS. That website also contains pages, at reader-selectable levels of complexity, which look at the specific claims of global warming deniers. So if you don't want to download the guide, it's still pretty interesting to just browse a bit.
It's not necessary, as I say, but it's still interesting.