If things go according to plan, we get climate control—and then need to worry little about either warming or reglaciation. The problem is things not going according to plan.
And if we do get hit by an asteroid, the last thing we probably want is runaway climate change started when we didn’t know what we were doing either.
Indeed. The “runaway climate change” we are scheduled for is reglaciation. The history of the planet is very clear on this topic. That is exactly what we don’t want. A disaster followed by glaciers descending over the northern continents could make a mess of civilisation for quite a while. Warming, by contrast doesn’t represent a significant threat—living systems including humans thrive in warm conditions.
Living systems including humans also thrive in cold conditions. Most species on the planet today have persisted through multiple glaciation periods, but not through pre-Pleistocene level warmth or rapid warming events.
Plus, the history of the Pleistocene, in which our record of glaciation exists, contains no events of greenhouse gas release and warming comparable to the one we’re in now, this is not business as usual on the track to reglaciation. Claiming that the history of the planet is very clear that we’re headed for reglaciation is flat out misleading. Last time the world had CO2 levels as high as they are now, it wasn’t going through cyclical glaciation.
Most species on the planet are less than 2.5 million years old?!?
I checked and found: “The fossil record suggests an average species lifespan of about five million years” and “Average species lifespan in fossil record: 4 million years.” (search for sources).
So, I figure your claim is probably factually incorrect. However, isn’t it a rather meaningless statistic anyway? It depends on how often lineages speciate. That actually says very little about how long it takes to adapt to an environment.
The average species age is necessarily lower than the average species duration.
Additionally, the fossil record measures species in paleontological terms, a paleontological “species” is not a species in biological terms, but a group which cannot be distinguished from each other by fossilized remains. Paleontological species duration sets the upper bound on biological species duration; in practice, biological species duration is shorter.
Species originating more than 2.5 million years ago which were not capable of enduring glaciation periods would have died out when they occurred. The origin window for species without adaptations to cope is the last ten thousand years. Any species with a Pleistocene origin or earlier has persisted through glaciation periods.
If things go according to plan, we get climate control—and then need to worry little about either warming or reglaciation. The problem is things not going according to plan.
Indeed. The “runaway climate change” we are scheduled for is reglaciation. The history of the planet is very clear on this topic. That is exactly what we don’t want. A disaster followed by glaciers descending over the northern continents could make a mess of civilisation for quite a while. Warming, by contrast doesn’t represent a significant threat—living systems including humans thrive in warm conditions.
Living systems including humans also thrive in cold conditions. Most species on the planet today have persisted through multiple glaciation periods, but not through pre-Pleistocene level warmth or rapid warming events.
Plus, the history of the Pleistocene, in which our record of glaciation exists, contains no events of greenhouse gas release and warming comparable to the one we’re in now, this is not business as usual on the track to reglaciation. Claiming that the history of the planet is very clear that we’re headed for reglaciation is flat out misleading. Last time the world had CO2 levels as high as they are now, it wasn’t going through cyclical glaciation.
Most species on the planet are less than 2.5 million years old?!?
I checked and found: “The fossil record suggests an average species lifespan of about five million years” and “Average species lifespan in fossil record: 4 million years.” (search for sources).
So, I figure your claim is probably factually incorrect. However, isn’t it a rather meaningless statistic anyway? It depends on how often lineages speciate. That actually says very little about how long it takes to adapt to an environment.
The average species age is necessarily lower than the average species duration.
Additionally, the fossil record measures species in paleontological terms, a paleontological “species” is not a species in biological terms, but a group which cannot be distinguished from each other by fossilized remains. Paleontological species duration sets the upper bound on biological species duration; in practice, biological species duration is shorter.
Species originating more than 2.5 million years ago which were not capable of enduring glaciation periods would have died out when they occurred. The origin window for species without adaptations to cope is the last ten thousand years. Any species with a Pleistocene origin or earlier has persisted through glaciation periods.