the human-made extinction
There are people who, regarding climate change, "think it has all happened before" and that it "will sort itself out naturally." These people are correct; climate change has happened before and life will recover from it as it sorts itself out naturally.
During the long prehistory of the Earth, the carbon dioxide levels in the atmosphere have been up to 20 times higher than they are now, and the surface temperature has been much higher, so the climate has changed drastically, and yet life is still here.
Climate change "has all happened before" many times during the Earth's existence; the worst of these occurrences are disastrous, and are called mass extinctions. In a mass extinctions more than 75% of all species become extinct (and a much higher proportion of all living things die). Climate change was part of the cause, or part of the process, of most of these mass extinctions.
There have been five major extinction events; the greatest of these occurred 251 million years ago: the Permian–Triassic extinction event, which nearly ended life on Earth. This event was probably initiated by massive volcanic eruptions, which covered two million square kilometres of what is now Siberia in lava flows. These volcanoes ignited massive coal deposits, possibly burning three trillion tons of coal. Lava flowing into the sea released methane that was trapped in ice on the sea bed. Initially, the volcanoes and the burning coal caused global cooling due to the ash that was released, but they also released a lot of carbon dioxide (a greenhouse gas) into the atmosphere, which, with the methane from the sea bed (another greenhouse gas) caused global warming and ocean acidification. Global temperatures increased very quickly by about 6°C near the equator, and more at higher latitudes, causing massive climate change.
The consequence of this climate change was that 90% of all species, and a much greater proportion of all life forms, were wiped out. Obviously, life recovered from this disaster. If fact, there have been two other major extinction events since the Permian–Triassic extinction event and life recovered from these, too.
So how long does life take to recover from these disasters? For most of the five major extinction events life "sorted itself out naturally" in five to ten million years; however, the Permian–Triassic extinction event was so severe that life didn't even start to recover for four million years and didn't completely recover for thirty million years. So indeed: climate change has happened before, and life has recovered from it, but it's a huge disaster, and it takes a long time to get over it.
Today, yet again, a vast quantity of greenhouse gasses is being released into the atmosphere as vast quantity of fossilised carbon (coal) is being burned. The initial global warning that this is causing is likely to release methane from the sea bed again. The big difference this time, is that this is not being caused by events that are out of the control of life, but by event that are caused, by choice, by one particular form of life.
And how is our own extinction event coming along? Well, the Qld Museum website says that the current rate of extinction, which is being brought about by human initiated climate change and other human initiated causes, is estimated to be somewhere between 100 and 1000 times greater than during any of the previous extinction events.
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