No offense, because this is complicated stuff and IANA climate scientist - but this is a really serious topic, and I'd really recommend you spend some time stud

No offense, because this is complicated stuff and IANA climate scientist - but this is a really serious topic, and I'd really recommend you spend some time studying the basics before posting a bunch of denialist-type stuff online where you may seed doubts to others. I would highly recommend a couple background, approachable videos on the topic from mainstream experts: * 11 min, Glen Peters, climate scientist: https://www.youtube.com/watch?v=529Og_YR0IU https://www.youtube.com/watch?v=529Og_YR0IU * 53 min, Kevin Anderson, climate scientist: https://www.youtube.com/watch?v=ZF1zNpzf8RM https://www.youtube.com/watch?v=ZF1zNpzf8RM To answer your specific question: paleoclimate has varied for many reasons, from solar and ecological changes to ongoing natural processes. CO2 is absorbed by the biosphere - by acidifying oceans, by plants that capture carbon then die and don't decay it all back into the air/water. The problem is this cycle is far too slow and low in capacity in human-relevant periods of time, relative to our present emission levels (or politically achievable fractions thereof). The biosphere is already absorbing about half the CO2 we emit, and there's evidence that share may be dropping as we overload its capacity in myriad ways (see today's permafrost bubble story as an example of a carbon sink turning upside down). Just as a final ironic point - where do you think all the CO2 we're emitting is coming from? From carbon sequestered naturally over millions of years into oil, natural(!) gas and shale/tar sands/etc. The natural processes that put it there are what resulted in the climate we have today. We're literally digging up the carbon that millions of years ago kept the planet warm enough for dinosaurs and pumping it back up into the atmosphere. That climate is the mean to which we will return.