>After adding all the uncertainties of the proxy data and our models (which we use to calculate temperature throughout Earth's history) it's not that sure chang

>After adding all the uncertainties of the proxy data and our models (which we use to calculate temperature throughout Earth's history) it's not that sure change like this has never happened before, or that it is happening faster than ever before. This is misleading. The rate of human injection of CO2 into the atmosphere has no analogue in the past, at least we've not found a similar excursion as yet. What effect this will have on the global climate system is inherently unpredictable, again, because we lack analogues from the past. What we do know is that global climate state changes have occurred rapidly; indeed, the whole Pleistocene is distinct in that the global climate system seems to have been in a boundary state in which it flips, sometimes within 50 years, from cold to warm, or the reverse. So that can serve as an analogue for how the global climate system can respond when perturbed. I say "have been" in the paragraph above because, in terms of atmospheric CO2 concentration, we've already exceeded any level observed during the Pleistocene. (And, not to belabor what I hope would be obvious by now, we have many lines of evidence that indicate with a high degree of certainty that it was human emission of CO2 in the last 150-200 years that has caused the spike in atmospheric concentrations.) Hence, researchers are looking to periods such as the Miocene and the Pliocene for a world that had continents in roughly the same configuration, but was much warmer, and, moreover, was warmer in a global pattern that fundamentally differs from that of the Pleistocene. We also have paleo-analogues for the effects of large increases in atmospheric CO2 concentration, and those are: acidification of oceans, ocean basin wide anoxia, local (confined, for example, to a particular ocean basin, or to a given depth range in oceans) and global extinctions, and interruption of the global oceanic thermo-haline circulation system. Another commenter stated that humans are as adaptable as roaches, and I'm afraid that this, too, may be a bit optimistic. In general, species resident at the highest trophic levels, with larger body sizes and habitat areal requirements, tend to be more vulnerable to change, and therefore to extinction, and thus tend to be much more ephemeral than smaller species in the fossil record.