What technology and cost would it take to scrub earths atmosphere to stop global warming?

Answer 1

That's a very good question you've asked and there are several schemes currently being researched that would help offset global warming. Some of these schemes are just what you have in mind - carbon dioxide scrubbers.

One device is nicknamed an artificial or synthetic tree - partly because it removes CO2 from the atmosphere (like a tree does) and partly because the panel is mounted atop a large pole and resembles a tree. Here's an artists impression -
http://www.americanenergyindependence.com/images/GRT-prototype.gif

The system works by capturing carbon dioxide directly from the atmosphere using a chemical process and the cost to set up has been calculated at 1.6 trillion dollars and a further 330 billion dollars a year to run.

There's loads of technical info about the scheme here - http://www.netl.doe.gov/publications/proceedings/01/carbon_seq/7b1.pdf and a lengthy document about CO2 sequestration in general here - http://www.centre-cired.fr/perso/haduong/files/Keith.ea-2005-ClimateStrategyWithCO2CaptureFromTheAir.pdf

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SOME NUMBERS
Each unit can capture 90,000 tons of CO2 and an estimate of the number of units needed has been put at 380,000. This would remove 34.2 billion tons of CO2 from the atmosphere each year. This is 5 billion tons more than were produced in 2006. Whilst the cost may sound prohibitively high when it's spread out across the world then it averages about $250 per person in capital costs and $50 a year in running costs.

Answer 2

By scrubbing, if you mean taking out carbon dioxide, one is already known: grow trees (or other form of vegetation) or iron hypothesis (something they tried a few years ago - basically dumping a lot of iron in the oceans to increase phytoplankton and eat up more carbon dioxide) and there has been research on having big ponds filled with CO2 absorbing stuff (like NaOH, Mg(OH)2), and after a few chemical reactions, you extract CO2 and dump it somewhere safe.

The first one you already know how much it will cost. Second one, not a whole lot, just a whole lot of iron and sulfur (actually they used ferrous or ferric sulfate I think) - you can read about iron hypothesis to get good numbers.

I don't think third one is going to be economical enough for a very long time, if at all.

As far other chemicals (methane, CFC and other fun stuff), no big technology - you just hope it will rain often and wash out the air periodically or just wait for them to break down slowly over time and we do a better job of making our power plants and cars and other technologies better to reduce those emissions.

Answer 3

This question assumes that "scrubbing" the atmosphere can actually stop global warming. This may be a scientific stretch.

Answer 4

Right now there is no practical way to do this. Plants are trying, but they're fighting a losing battle.

Look at this graph.

http://scrippsco2.ucsd.edu/graphics_gallery/mauna_loa_record/mlo_record.html

The little squiggles are nature doing its' thing. CO2 falls a bit during summer when plants are active, and rises during the winter. The huge increase is us, burning fossil fuels. The natural carbon cycle buried carbon in fossil fuels over a very long time, little bit by little bit. We dig them up and burn them, real fast. That's a problem.

So, while we try to develop a technology to do this we need to stop CO2 at the source. That means conserving energy, and developing alternative energy, nuclear, solar, wind, biofuels.

There's no magic machine to save us. It will take hard work.