The fundamental problem with all the global warming (now termed 'climate change') data is that nearly all of it is just 'estimates' and approximations and guesses. There is simply no truly reliable way to calculate global temperatures even just a few hundred years ago, much less tens of millions of years ago, etc. I believe it is accepted that modern man's first visits to the North and South poles in any kind of scientific expedition were in the past 150 years, for example. Much of the world's oceans are barely mapped, let alone carefully and accurately measured for exact temperatures, etc.
We may be able to determine that the planet has experienced significant rises and falls in global temperatures as evidenced by the so called ice ages and so on. The many theories, reasons, etc for the warming and cooling of the planet are reasonable guesses for what happened but it is much more difficult to determine with certainty why.
The climate is influenced in many ways by many events, conditions, and activities from the activities and impacts of mankind to those of each and every other species of plant and animal from the past, the present and the future. The environmental systems which are in a constant state of change and evolution influence temperatures and many other factors which in turn impact temperatures. Solar energy is the primary source of heating of the planet - nearly all can agree on this. The sun and its energy emissions change in intensity and duration. Volcanoes, earthquakes, impacts of meteors and asteroids, etc. The release of the so called greenhouse gases and myriad other conditions create circumstances whereby local, regional and global temperatures and climate as a result will vary. We don't know which have how much influence at any given time over the millions and millions of years of the Earth's existence.
