If you were to believe global warming deniers, climate change is all right because the climate changes all the time.
True enough; but the last time atmospheric carbon dioxide levels were sustained at 387 parts per million (ppm) was 15 million years ago, during the Burdigalian stage of the Mioscene Epoc, according to XXXX of UCLA in his paper XXXX.
Unlike now, 15 million years ago CO2 levels were on their way down, allowing global temperatures to slowly cool and ice sheet to be formed on the poles. Grasslands underwent a major expansion; forests yielded to a generally cooler and drier climate overall.
There were evolutionary losers; the closest relatives to elephants and sea-cows, the Desmostylians, became extinct. But we early chimp-hominids did rather well out of having to stand on two feet at the edge of the forest to scan the savannah for the saber-toothed predators or the ruminant prey co-evolving with the greatly diversifying grasses. By the time our primate ancestors had evolved into early man, co2 levels were stabilising, the carbon cycle settled, the world’s temperate regions started to become established, and the climate started to follow the wobble in the axis of the earth as it travels around the sun.
Both human (Ardipithecus, Australopithecus and Homo) and chimpanzee (Pan troglodytes and Pan paniscus) lineages diverged from a common ancestor about 5 to 6 million years ago and the climate became more benign, steadying into a pattern of ice-ages of low atmospheric CO2 punctuated with long interglacial periods.
Greenland started becoming covered in ice three million years ago when high atmospheric carbon dioxide levels dropped to levels closer to that of the pre-industrial era, and methane became trapped in the permafrost in the tundra of the high latitudes.
This suited Australopithecus, who lived, and could now follow the seasons that were forming as Africa’s climate started getting drier, making hunting and gathering predictable enough to develop stone tools. Their brain was 35% of the size of the modern man, big enough to help them exploit the forest and grassland habitats that got them their varied and seasonal diet.
Peak CO2 levels over the last 2.1 million years averaged only 280 ppm; today, CO2 is 38% higher.
Then a between 2.5 million years ago and 1.5 million, after Australopithecus evolved into Homo erectus, our brain grew from 600ccm to what it is now, about 1350ccm. The drying climate forced us to develop language to learn to get food in more adverse circumstances. We became serious tool makers and started wearing clothes as we headed out of Africa to Europe. Handily, we had tamed fire, so we were in good shape to tackle the next series of ice-ages. Pleased with ourselves, we developed jewelry, and then social hierarchy. In short, our current interglacial periods, called the Holocene, has been stable climatically and this has witnessed Homo sapiens explode into the Bronze Age, into agriculture, into civilisation, and into history. It’s been one wild ride, one that’s included a trip or two to the moon.
Not bad for that early chimp-hominids standing on two feet at the edge of the forest peering over the savannah grasses those fifteen million years ago, wondering what its chances of a good meal were.
But we really do owe our success to a stable climate.
Over the last 20,000 years our population has boomed from 6,000 to 6,000,000,000, most of that during the last 8,000 years of the 12,000 year Holocene, during which the average pre-industrial CO2 levels are 280 ppm. Now, instead of throwing rocks we got the bomb. We’ve played with remote control buggies on Mars, and we get pics from our probes pressing ever on into the reaches of our galaxy.
However, not without a cost; having poured enough CO2 into the atmosphere to change the climate since 1850, long-term temperature trends have been going up at a rate unprecedented in all geologic time. Today, we find CO2 concentrations at 387ccm again, only this time the trend is on the way up, not down, and we don’t have the same benign prognosis as faced us last time, over that savannah clearing. Biodiversity, on which a healthy and bountiful environment depends, is predicted to fall, not grow like it did last time. Variety of food available to us will shrink as food chains fall apart and ecosystems fail, and economies falter. We know from past experience that the great carbon sinks of the planet, the oceans, will become more acidic eating away at the calcified micro biology of the bottom of the ocean, wiping it out. Already we can see that the permafrost is not so permanent, belching methane as it warms up. You might have seen the famous farting ice on You Tube.
This time, despite the prognosis we face under a business-as-usual scenario, we do have one major advantage: We don’t drag our knuckles on the ground any more, and as we survey our future for risk and reward, we have an understanding of the world we face, and how we impact it, and what we have to do to reduce that impact to a sustainable one.
The moral of the story of man is that we are happiest when living in the predictable climate of our pre-industrial years.
Global Warning Climate Change Energy