About climate change: It is actually very rare that the climate has been as stable as it has been for the past centuries. Of course climate change is happening, because it is an on-going process of nature.,(reply>), @icedragon769 In fairness, we do encounter climate change events happening at this speed occasionally in the past, but, as you predicted, mass extinctions usually follow.<br><br>Incidentally, people sometimes take "it's happened before" to be conclusive proof humans aren't behind it.  That's hardly the case.  In the vast majority of instances, climate change has been kickstarted by an increase of CO2 in the atmosphere from various sources (we know this due primarily to ice core examination), and the concentration of CO2 is once again increasing right now.  It just so happens that, rather than a supervolcano or the like, the cause is humans.,(reply>), What's that even supposed to mean? You cannot measure the past instability of climate, only big-picture trends, and the big-picture trends is that the climate stays more or less the same, taking thousands of years to change as much as 1º. <br><br>If there were fluctuations as big as this one in the past, it would have caused mass extinctions that would be detectable, there are no such events. Ecosystems cannot survive this rate of climate change.,(reply>), Until you hit the mid 20th century, then it skyrockets.  Now, we're about 1C above the 20th century average, and will probably, at the current rate, hit 4C by the century's end.  To put that in perspective, the ice age was 4C below the 20th century average.  This isn't a good thing, and its tied directly to an increase in carbon emissions.  Which are also not good things.