Al Gore's Earth in the Balance 3

In my latest reading of Earth in the Balance: Ecology and the Human Spirit, Al Gore talks about the dramatic effects of shifts in climate throughout history, as they led to such things as famines, migrations, plagues, and competition for resources.  In some cases, Gore notes, volcanoes caused these climate shifts.  On page 73, Gore states his point behind giving us this history lesson: "All of these changes in climate patterns took place during temperature variations of only 1 to 2 degrees Centigrade.  Yet today, at the close of the twentieth century, we are in the process of altering global temperatures by up to three to four times that amount and causing changes in climate patterns that are likely to have enormous impacts on global civilization."  Such consequences would include migrations----as the rising sea level would displace some people and soil erosion would render subsistence farming impossible in certain locations----and the political conflicts that could result from that.  Moreover, the hole in the ozone layer makes people less resistant to disease in certain areas, and "populations of pests, germs, and viruses migrate with the changing climate patterns" (pages 74-75).

The reason that this discussion stood out to me was on account of right-wing arguments that I have heard about climate change: that the climate has historically gone through cycles that had little to do with human activity, that natural things such as volcanoes pump a lot of pollution into the air, and that the global temperature has only gone up a few degrees.  Gore acknowledges that there have been climate fluctuations throughout history, that volcanoes have sometimes contributed to that, and that there have been times when the temperature has only gone up by a few degrees.  But, for him, that is not inconsistent with human activity contributing to climate change, and climate change (even by a few degrees) having disastrous effects.