Only in the last million years, there have been at least nine glaciations, ie one every 100,000 years or so. The current warm period, the Holocene, is not over yet, paradoxically thanks to the reviled global warming, although it will end inevitably sooner or later. As a premonition it says rightly in the TV serie, Game of Thrones: “Winter is coming.”
During most of life of the planet Earth, it has lacked polar ice caps, until approximately between 80 and 40 million years ago when Antarctica, separating from Australia, changed its track to its current position and began to accumulate ice. The previous interglacial period 127,000 years ago, we know that was warmer than it is today. The last ice age began about 100,000 years ago, although the problems for humankind rushed about 70,000 years ago, when the monstrous eruption of the volcano of the Toba island, worsened the weather conditions to take us almost to the point of extinction, with a rate of survival of only about two thousand people worldwide, “evolutionary bottleneck” is what the experts call, to fuck it up to the bone in Biological terms. It is difficult to imagine how it had to be, but surely the volcanic winter that lasted about seven years prevented photosynthesis, drastically affecting the food chain.
Then suddenly, about 12,000 years ago, global temperatures increased for many reasons (solar, cosmic, geophysical) and none. The interglacial periods last a breathe, in geologic time, between eight and twelve thousand years. This process has been happening regularly since about 2.4 million years ago, coinciding with the emergence of the genus Homo, with Homo habilis specifically, who was sufficiently different from primate Australopithecus, according to experts. The dancing of the figures for the origin of Sapiens Sapiens is disheartening: under the mitochondrial DNA tests are set at about 200,000 years ago, but other genetic studies set 140,000, and even some molars found in Israel, would raise the figure to 400,000 years. In any case the extreme cold, extinguishes, freezes or slows down the chemical reactions and also the life’s cycles, but the human being is perhaps more than any other being, the species from ice , although at the present, it costs us believe it. Maybe that’s why we love the fire, that’s why the desire of humanity to be free from slavery and the harshness of the environment, the taste for artifice, tools, clothes, shoes and something largely ignored, navigation since very early time, more than many can imagine .
Now everyone is very sensitive against global temperature increase and I will not be who belies all the researches about it, but I do not think we have an idea of the traumatic repercussions for life involved in an ice age, a phenomenon often associated with mass extinctions, a landmark of the utmost importance from the point of view of natural selection. Apparently we have to be careful with what is intended: a decrease of the current level of carbon dioxide to the half, is enough to trigger a new ice age.
Maybe we should not worry, the supposed smarter being of the planet, should be able to survive, but it’s sad that the only plan, put it in some way, quite unconscious, to withstand a decrease of temperatures from about 15 ° C in the warm regions, is based on the current number of inhabitants and the depressing prospect of that a few can get it, a plan certainly not very different from that of baboons. Ronald Reagan once said that an alien threat would be a good glue to attach humans against a common enemy, since its militaristic perspective and experience in show business perhaps he could not imagine that people has enough reasons to leave aside dogmas as the nationalism, and an unmissable event that probably will end billions of lives; stellar conflicts at the style Starship Troopers will not be necessary.
Ice ages are a well-documented reality, and it gives the impression that we are not considering it how it deserves. So I do not look so bad a relatively small rise in global temperature, although ideally, of course, would be that this increase was due to a controlled system, we should know an effective control mechanism to maintain thermal equilibrium, that is one of the tasks that humanity as a whole will have to face, it is not a job for a single country or a multinational corporation, you can not leave the operation of the climate in the hands of private interests. Earth is still our only home.