Well, it's official, folks. Global warming will indeed cause life on Earth to end early, in a manner linked to CO2. Not great news if you believe in the strong Gaia hypotheses. There are a couple of earlier mass extinctions that are even less good news, and as for our future:
"The starting point is that the sun is getting hotter. It has increased in brightness by about 30 per cent over the past 4.5 billion years and will carry on doing so. As the sun continues to burn brighter it will cause global warming, which will translate into increased weathering of silicate rocks - the rate of weathering rises with temperature. This will remove CO2 ever faster from the atmosphere, aided and abetted by photosynthesis and plant roots. At first, this removal of CO2 will buffer the solar-induced temperature increase. But there will come a time - possibly as early as 500 million years from now - when there is not enough CO2 in the atmosphere to support photosynthesis. When that calamitous day arrives, a very pronounced end of the world as we know it will begin...."
Might we have to worry about, say, the direct effects of increased insolation first?
AvatarADV, unlikely. The planet's temperature has been quite steady despite the aforementioned 30% increase in brightness over the life of this planet so far. There are various mechanisms that could explain it, clouds are one of them. These same effects are one of the major reasons why I think it's unlikely that adding CO2 to the atmosphere will have any major effect on temperature.
So, I think it's likely whatever mechanisms have kept temperature relatively stable up until now (in and out of ice ages and glaciations of course, which theories suggest may be controlled by continental drift), will continue to do so into the foreseeable future.
If humans are still around in 500 million years, they may have to start burning a whole heap of stuff to make sure there's enough CO2 in the atmosphere for plants to survive...
If human beings are around 500 million years from now, they'll just do some stellar engineering and fix the sun. Or move the Earth out to a wider orbit. Either of those is quite doable if you're rich enough and have a few hundred thousand or million years to wait.
I'm seeing Idiocracy plus sharia as a more likely future for mankind, with occasional nuke strikes for reasons of derka derka derka. That won't leave any money for grand engineering, even if the will and the wits were there.
On the good side, in this scenario, when the lights finally go out for mankind nothing of value will be lost.
In such a case, humanity won't last even another 100 Kyears, much less 500 Myears.
Who's going to pay to rescue all those Terrans before they cook like cabbage rolls? The hard-working, tax-paying colonists of Alpha Centauri, that's who. Same people who will pay for the John Murtha XXXXIX Spaceport.
Joke mode off for a moment, that's a good piece of science writing. I used to think that the Gaia idea (which I now realize was three ideas) was interesting, attractive and not quite convincing. I now see it as attractive but definitely wrong.