The concept of carbon sequestration as a solution to global warming seems idiotic, why isn't it? Or is it?

Sequestering carbon dioxide is basically the reverse of the process that brought all that carbon up to the surface. Geologic sequestration makes lots of sense and is already being done for reasons other than global warming. Ocean sequestration is much more uncertain, and I have to agree with your skepticism about this, as it seems not only to be temporary, but likely to have dangerous ecological impacts.

Carbon dioxide is already pumped into oil reservoirs as a method of retreiving more oil. However the source of that carbon dioxide at present (in most cases) is from underground reservoirs that happen to have large amounts of CO2. There is actually a carbon dioxide pipeline that runs from Colorado to Texas just for this purpose, and the oil companies that use it obviously consider it to be economical.

http://www.cortezjournal.com/asp-bin/article_gener...

If carbon dioxide from a coal-fired power plant were pumped underground it would have both beneficial environmental effects, and might prove to be a future raw material for methanol production (CO2 can be made into methanol). Here is one of the research projects related to this:

http://www.beg.utexas.edu/environqlty/co201.htm

Here is some information on converting CO2 to methanol:

http://www.technologyreview.com/read_article.aspx?...

The ocean sequestration idea has a number of variations, most of which acknowledge that there is an unknown impact on the ocean ecosystem. For this reason most of these may prove that the cure is worse than the problem. One idea is to add iron to the southern ocean. Since iron is a limiting nutrient for phytoplankton in that region, there would be increased biological activity. This could have lots of unforeseen problems (for example at some point those phytoplankton might cause eutrophication). Likewise, directly injecting CO2 into the deep ocean would not only be just a temporary place to store the carbon, it could have strange geochemical effects on things like the calcium carbonate compensation depth, and would undoubtably affect deep ocean biota.

Here is one perspective that does not support ocean sequestration:

http://www.sciencemag.org/cgi/content/summary/300/...

Here is a DOE site that has abstracts of ocean sequestration research:

http://cdiac2.ornl.gov/ocean.html

As for the comment about taxpayer expense: There is some research funded by DOE, which is taxpayer expense. However, 1) taxpayers USE the oil, 2) Oil revenues are the SECOND largest source of government revenues behind the IRS(not even counting gasoline taxes- this is just oil royalties paid by oil companies to the US government), and 3) Taxpayers will reap the benefits of any research into carbon sequestration, not oil companies.

By itself CO2 sequestration isn't a solution to global warming. However as a component to comprehensive plan it could be very useful. In order to return the world's CO2 levels the those of the 18th century we not only have to stop releasing CO2 into the atmosphere we must also remove the excess amounts. Nature sequesters CO2 in plants, in the ground, and in ice. Putting CO2 back in the ground doesn't seem like a dumb idea to me. How else should we be lowering CO2/ green house gases levels?

Carbon sequestration is not idiotic. Removing the CO2 that forces atmospheric warming should cool the planet, ton per ton, degree for degree.

We are not limited to just two methods. Personally, I am suspicious about pumping CO2 into the oceans. I prefer using plants or bacteria to capture CO2 and then burying it in the earth.

Mostly I've heard of terrestrial sequestration... putting CO2 back into oil reservoirs that have been drained. Right now, with modern technology, we would have a lot of technical issues, mainly with efficiently collecting the CO2 and keeping in wherever we put it.

Clearly, limiting our CO2 would be better than trying this. Of course, increasing biologic intake might help too, but them we might screw up ecosystems even more then they already are. One idea is adding iron to the ocean, because Fe is the limiting element to photosynthesis to phytoplankton. But again, what happens to the rest of the food chain?

Well, you might say burning the stored carbon was the mistake.

We have released carbon dioxide that it took photosynthesis millions of years to lock into fossil fuels.

Even if we stop burning all fossil fuels now, it will take at least 1,000 years for the carbon dioxide to be recaptured by plants.

So if carbon sequestration were to be viable it would offer probably the only chance for us to fix what we have done within the lifetimes of the next few hundred generations.

The oil company's want to pressurize the wells with CO2 to recover more oil a the tax payers expense.

We can sequester CO2 by planting billions of trees.