We Can Work It Out
Of course, there is plenty of proof. However, this comes down to a matter of philosophy. If humans aren't the cause, then we can't be expected to do anything about it. We just blame it on nature and then sit back and wait to "adapt".
However, if we accept that humans are contributing to global warming, it is incredibly empowering. If we can cause the problem, we most certainly can at least mitigate that problem. Isn't that a much better attitude?
Here's the rub. If we are causing the problem, then there seems to be some kind of moral imperative to address the problem. And that might mean that someone will suggest that they make a lifestyle change, or will impose a new tax or regulation. If you deny the problem, then you can deny any solution you don't like as more socialist conspiracy. And you can turn a purely scientific discussion into a political one.
Ok, three posts in a row with titles taken from Beatles songs. The first two were coincidence, but I'll admit the third was deliberate.