A Hidden Loop In the Carbon Cycle Discovered

Googlesaysmysiteisdangerousanditisn't! writes "A recent article in Science says that researchers in China and the US have found massive carbon uptake in the world's deserts. The effects of this are huge. 35% of the Earth's land surface is desert, and the uptake equates to 5.2 billion tons of carbon sequestered each year. This is more than half of the carbon released by humans. In these 'dry oceans,' the grains of sand allow the carbon dioxide to enter and react with alkaline soil to become carbonates. Another scientist suspects that biotic desert crusts, alkaline soils, and increased precipitation may be driving the uptake."

Comments

Re:Obviously

[Captain Splendid]

The solution is obviously to cut down more trees and make more deserts, right?

Sure, as long as you don't skimp on the sandworms.

Re:Sooo...

[Anonymous Coward]

No, the prolific amount of oil in the Middle East is mainly related to organic carbon in source rock deposits that formed in the marine environment. The source rocks in the Middle East are particularly widespread and productive.

The article is talking about carbonate (i.e. minerals with CO3 in their structure), which is completely different and is often referred to as "inorganic carbon". It's as different as algae (organic carbon) and sea shells (carbonate). They both involve carbon and both can have biological origins, but you can't generate oil from carbonate. You need molecules with plenty of H and C for that (i.e. hydrocarbon molecules).

You can, however, find holes in carbonate rocks. In the right setting these can contain oil that has migrated into the porous rock from organic-rich source rocks nearby. Such rocks are known as petroleum reservoirs. Again, the Middle East has some spectacular reservoirs with very high porosity and permeability, allowing for plenty of space to hold the oil and to allow it to flow out. For example, the Ghawar field, which is the biggest oil field in Saudi Arabia and the world, has limestone reservoirs with up to 35% porosity by volume -- i.e. 35% of the volume isn't rock, but open spaces filled with fluid (either oil, gas, or water). That's extraordinarily high porosity. It's full of holes like a sponge.

So, if you want the short answer to why there is so much oil in the Middle East: 1) spectacularly prolific and widespread organic-carbon-rich source rocks, 2) highly porous and permeable reservoir rocks (some of which are carbonates, some of which are other rock types), and 3) large "trap" structures, which I haven't discussed, but basically refers to the geometry of the porous reservoir and an impermeable seal that keeps the oil/gas from leaking out.

It has very little to do with the modern deserts that are widespread in that part of the world today. Many of the conditions necessary for the large oil deposits were set up far enough back in geological history that today's climate is mostly irrelevant.

Misleading Summary

[Conspicuous Coward]

TFA is far more cautious about these findings than the summary suggests. Also, no scientists are currently suggesting that these findings are likely to have a significant impact on the level of anthropogenic global warming.

The effect could be huge: About 35% of Earth's land surface, or 5.2 billion hectares, is desert and semiarid ecosystems. If the Mojave readings represent an average CO2 uptake, then deserts and semiarid regions may be absorbing up to 5.2 billion tons of carbon a year.

Also...

For now, some experts doubt that the world's most barren ecosystems are the longsought missing carbon sink. "I'd be hugely surprised if this were the missing sink. If deserts are taking up a lot of carbon, it ought to be obvious," says William Schlesinger, a biogeochemist at the Cary Institute of Ecosystem Studies in Millbrook, New York, who in the 1980s was among the first to examine carbon flux in deserts. Nevertheless, he says, both sets of findings are intriguing and "must be followed up." Scientists have long struggled to balance Earth's carbon books. While atmospheric CO2 levels are rising rapidly, our planet absorbs more CO2 than can be accounted for.

and...

Provided the surprising CO2 sink in the deserts is not a mirage, it may yet prove ephemeral. "We don't want to say that these ecosystems will continue to gain carbon at this rate forever," Wohlfahrt says. The unexpected CO2 absorption may be due to a recent uptick in precipitation in many deserts that has fueled a visible surge in vegetation. If average annual rainfall levels in those deserts were to abate, that could release the stored carbon and lead to a more rapid buildup of atmospheric CO2--and possibly accelerate global warming.

This is not, as some posters are implying, published science that concludes the IPCC predictions are in any way likely to be inaccurate, or that carbon is accumulating in the atmosphere at a rate lower than previously thought.
This is a news article in science detailing some interesting research showing that deserts may be absorbing more carbon than was previously thought, and that this may account for the fact that atmospheric measurements show the earth is absorbing carbon at a higher rate than can be accounted for by currently known sinks. The amount of CO2 in the atmosphere is known from atmospheric measurements, and is higher than at any time in the last 650,000 years.

The European tax effect

[Kupfernigk]

In fact you are right, and the net result is interesting. In Europe we pay about the same PER MILE for fuel as you do in the US, even though it costs twice as much per gallon. The high tax causes most of us to buy fuel efficient cars, our smaller city streets (built before cars) encourage us to use smaller vehicles. But our road deaths are no worse than the US and often much better.

The problem with CAFE was that it was indeed a boondoggle - the mandated efficiency improvements were actually less than were achieved automatically by European taxation levels, and as you note it was easily evaded with the "light truck" class.

Taxation of fuel is sensible because it is a tax on actual consumption. Most people are able to reduce their consumption by varied means - aggregated journeys, car shares, vacations closer to home, reducing acceleration, using mail order more - without changing their vehicles.

Re:Fragile Earth or Robust Earth?

[meringuoid]

I've afraid you're the one whose bought into a common lie. Human activity releases far, far less carbon dioxide than the planet produces.

Indeed? Then I'd like to see your figures. Because we outdo the volcanoes by a factor of a hundred. Looking into other sources, well: rotting vegetation was mentioned, and I agree it's a far larger quantity than human activity, but is that a source of carbon dioxide? Rotting vegetation can never release more carbon dioxide than the amount it absorbed when it first grew, making it net carbon neutral. Unless there is a net decrease in the planet's biomass, there's no overall extra carbon dioxide in the atmosphere due to plant life. Same goes for respiration by living things: the CO2 I exhale is carbon that was absorbed when my food grew, and will be absorbed again as a future meal grows.

We on the other hand are digging up and releasing vast quantities of carbon dioxide, all year, every year, and unlike the plants we're not taking it back out of the atmosphere. That's producing an ongoing year-on-year net increase in carbon dioxide. Nothing else on earth compares to human industry for increasing atmospheric CO2 concentrations.