Something I hear often from climate scientists, and indeed even politicians, is that we "don't understand climate change very well". And, I'm sure this is true since the climate is a complex adaptive system with thousands of dependent variables, one that we don't yet have the computational sophistication to accurately model. But that doesn't mean we don't know, to a high degree of accuracy, what is going to happen if we make certain changes to the atmospheric composition or take certain actions. We have paleoclimate data ranging extensively far back many hundreds of thousands of years, encompassing global temperature, climate cycling, atmospheric composition, and more.
Sure, the global temperature 100,000 years ago wasn't measured using a thermometer, but we've used various independent proxy methods that all agree with each other to a reasonable degree, right? And so do we not then have a reasonably accurate idea of Earth's climate sensitivity by simply looking at precedent? And paleoclimate will be close to exactly right since it takes all the variables into account exactly in the amount they're needed to be accounted for. Why are we still "uncertain" about the realities of climate change? Why are we not moving on and taking decisive action based on this--what seems to me--reliable, accurate data?