> Each year over the last 20,000 years has been hotter than the last, on average. The "chart has gone up" every single year since when campfires were the height of human technology.

If you look at the chart in the link above, it's very clear there has been a dramatic change in the last 50 years. There has also been a dramatic rise CO2 emissions in a similar period. I don't think its unreasonable to assume the two are linked.

Even if you were to concede we cannot prove that our emissions are causing the change, we should at least acknowledge that there is some chance that they are. We can't do anything about the earth naturally warming itself, so there is no action required in that scenario, but we can reduce our emissions in the chance they are damaging the earth.