Well, part of the problem is that by the time we really know for sure, it's probably too late to prevent massive damage. Oceans are slow to warm and also slow to cool. We have early warning signals (slight warming oceans leading to die-offs). We know that carbon dioxide, methane, and other gases trap heat in the atosphere. We know we are releasing these gases in prodigious quantities. And we know that temperatures are warming. It doesn't take much to connect the dots.
You skeptically say that it's been warming for the last 500 years, which is a convenient timeshot that cuts right out of the little ice age. But it's warming much more rapidly during the past 50-100 years, since industrialization occurred, and a natural trend doesn't explain this.
We can't say with absolute certainity what is going to happen until after the fact, so you're saying this argues for no action? I'd disagree. If you think there is 1 in 100 chance that an earthquake is going to occur, then you consider earthquake insurance. Based on the accumulated evidence the odds of global warming occurring are much higher. So, why wouldn't we take some precautions?
So, what would insurance be? We'd have to cut our fossil fuel consumption, probably drastically in the long run, but we could start moderately. This means we'd be developing energy sources within our country, building new jobs, rather than shipping our money to places like Saudia Arabia and Venezuela where it is probably going to be used against us. It won't happen now until oil really starts to run out because we subsidize fossil fuels. But with some economic incentives, we could have a homegrown energy economy, could worry less about the middle east, and would be building ourselves some breathing room on climate change at the same time. What is the downside to that?
There is slight overall warming, but it's the uneven warming that has led to some dieoffs. The rest of the dieoffs are due to other factors as they always have been. Even uneven warming has always been around and always will be irregardless of overall temperature.
But it's warming much more rapidly during the past 50-100 years, since industrialization occurred, and a natural trend doesn't explain this.
The warming in the first half of last century was followed by cooling until the 70's, then more warming. The warming is indeed part of the exit from the last ice age and the link from human-caused CO2 to warming is only a theory.
But with some economic incentives, we could have a homegrown energy economy, could worry less about the middle east, and would be building ourselves some breathing room on climate change at the same time. What is the downside to that?
It's a decent question and I'm not opposed to incentives. But I see hybrid cars that take more energy to build and maintain. They use more energy than a car with the same gas engine in many cases like open highway travel. I see ethanol that takes more energy to produce than it yields. There are other better alternatives, I don't see any downside to subsidizing solar in Arizona for example.