From Lubos: http://motls.blogspot.com/2012/01/will-co2-save-us-from-next-ice-age.html

[…]

Now, in the last 24 hours, BBC, The Telegraph, and many others wrote about a new paper by Luke Skinner et al. in Nature Geosciences. The paper says that CO2 will save us from the coming new ice age which is great.

It’s refreshing to see that CO2 is sometimes getting good press. You really don’t want the temperatures to drop by 10 °C. On the other hand, all the other “details” that are being written about these questions are preposterous beyond imagination.

It’s being said that the warm era between two ice ages is usually around 11,000 years #whatever is the exact definition of the boundaries# but we have already enjoyed over 11,500 years since the last ice age so a new ice age is overdue. Well, those things are not periodic so it is nonsensical to expect that it’s always the same 11,000 years. And I still don’t have the full Milankovič-Roe projection of the future ice ages so I can’t say whether the expectation is right. If they only use some analogy with the moment 780,000 years ago but ignore Roe’s model, then I will consider the claim untrustworthy.

Dynamics of CO2 concentration after fossil fuels

However, what’s even more absurd is the role that is being attributed to CO2. CO2 will only be modified due to the human activity for a few centuries which is much shorter than the time needed for the ice age cycles to collect several Celsius degrees – that requires thousands or tens of thousands of years.

In particular, we will probably run out of fossil fuels in less than 300 years. I am being generous here; my expectation would be lower. At the peak, there will be some concentration which may be anywhere between 600 and 2000 ppm. I don’t know how far the mankind will get. I am just sure that once the concentration will reach 1000 ppm, people will already be realizing very well that there’s nothing wrong about such elevated concentrations and they will be able to understand that 2000 ppm isn’t a problem, either.

[…]
via The Reference Frame: Will CO2 save us from next ice age?.

Lubos makes a point I try to make regularly. Humans have always burned everything they could, and we always will. We will run out of most things to burn within a few centuries. I think 300 years is a reasonable expectation. I think we have that much coal and oil, and maybe that much gas, but we are very likely to see usage go down within a few decades, and we might not ever actually run out of oil, we just won’t use much eventually. It will not be worth extracting. I don’t think we know what the alternatives will be, but I you can rest assured it will NOT be our food. We won’t stay that dumb for long. It hurts too much. I suspect alternatives to liquid fuels will not be bio-based. I expect we will always you some liquid fuels; they are just too useful. I’m certain most of our future energy will come from regular nuclear fission. We might figure out some method of fusion, but don’t expect your grandchildren to live to see it commercialized.

Anyway, the important point is that there is too little fossil fuel for it to matter in the long run. 500 years from now, only academic types will even remember what fossil fuels were. By then, no one will even remember that carbon dioxide and the burning were controversial.