Because there hasn't been enough data on weather changes in the last 400 million years there's no proof man is making any impact. You can argue either way but there's clearly been very cold temperatures during the Ice Age where some said Humans were maybe down to a population of 150-200 so therefore it is logical there were some periods of very high temperatures. It is very safe to say we are in the middle of it rising right now. However you need more time to really determine this. However why wait when you can tax the shit out of it now and scare the fuck out of everyone in order to buy votes and use it at times to get away from issues which hurt your party.
Non-sense, we have very accurate historically data, trees, ice cores etc. Like it's a fact, you are wrong, there has never ever been a rise in co2 this rapidly, using the ice cores of millions of years we can see that. We know our orbit, wobble, distance to the sun, solar output, volcanic activity, ocean currents, glacier density etc. it's not up for debate. You don't need more time, co2 has never risen this fast, it is lightening fast, we are seeing the 6th extinction level event in Earth's history, species cannot adapt this fast, co2 might be fine, but the rapid increase is crushing ecosystems right now, hence a MASS EXTINCTION.
We know the cycles of the earth, venus and mars also provide data on atmospheres, Venus is currently in run away greenhouse effect, due to methane, this can happen here.