More CO2 *good* for biosphere?

[Greebo]

In praise of CO2

With less heat and less carbon dioxide, the planet could become less hospitable and less green.

Excerpt:

The results surprised Steven Running of the University of Montana and Ramakrishna Nemani of NASA, scientists involved in analyzing the NASA data. They found that over a period of almost two decades, the Earth as a whole became more bountiful by a whopping 6.2%. About 25% of the Earth's vegetated landmass -- almost 110 million square kilometres -- enjoyed significant increases and only 7% showed significant declines. When the satellite data zooms in, it finds that each square metre of land, on average, now produces almost 500 grams of greenery per year.

Why the increase? Their 2004 study, and other more recent ones, point to the warming of the planet and the presence of CO2, a gas indispensable to plant life. CO2 is nature's fertilizer, bathing the biota with its life-giving nutrients. Plants take the carbon from CO2 to bulk themselves up -- carbon is the building block of life -- and release the oxygen, which along with the plants, then sustain animal life. As summarized in a report last month, released along with a petition signed by 32,000 U. S. scientists who vouched for the benefits of CO2: "Higher CO2 enables plants to grow faster and larger and to live in drier climates. Plants provide food for animals, which are thereby also enhanced. The extent and diversity of plant and animal life have both increased substantially during the past half-century."

Now I don't know how reliable this article is, but if its accurate, it's something to think about.

[OzFreeBird]

Its not quite that simple. CO2 is dissolved in vast quantities in the ocean and its dissolution rate is a function of temperatures (and to a lesser extent pH). When sea temperature rises, more CO2 is released as a gas.

All marine life with a calcareous structure needs CO2 to build themselves. This starts off with plankton right up to whales. If you take CO2 out of the ocean, not only do you get a runaway ambient greenhouse, you also start to cause animals with calcium in their shells (all shellfish and corals) to dissolve, thus the food for higher organisms (fish) disappears, thus the fish die, thus everything in the complex oceanic cycle dies. All you have left is a giant cesspool of murky green, anaerobic, highly acidic algal soup not too dissimilar to that seen at the end of the Jurassic when 95% of the world's biodiversity was wiped out.

Don't think I need to point out what that would mean for us.

[Greebo]

runaway ambient greenhouse

I feel compelled to do a little debunking. The idea of a runaway greenhouse effect is frequently touted, but the models which predicted runaway greenhouse effects were flawed, fundamentally. They assumed infinite atmosphere, something we definitely haven't got.

http://www.dailytech.com/Researcher+...icle10973c.htm

I'm not disagreeing with anything else you wrote - just about the whole runaway greenhouse concept.

[OzFreeBird]

I'm a geologist, not a physicist, so can't make much comment about atmospheric physics. Physics tries to predict what will happen in the future through mathematical modelling. Geology simply studies what has happened in the past, for which there is concrete evidence. Physics still can't explain chaos theory or anything involving atmospheres or fluids (including oceans) very well. That is why weather prediction is so difficult in a temporal sense; the inputs are too varied for physics to predict what will happen with any statistically acceptable degree of confidence.

Nature, which is probably the world's most respected scientific journal, released a paper this week about the past effects of CO2 and methane dissolution into the earth's atmosphere.

As I previously mentioned, 635 million years ago there was a rapid global warming event on an otherwise very VERY icy world, most probably through the effects of mass vulcanism, although the trigger is still fiercely debated by scientists.

This caused masses of CO2 and particulates to be emitted into the atmosphere. The result was that the sun's rays once penetrating the earth's stratosphere were unable to "bounce" back into space, were effectively trapped, and started to increase the ambient temperatures of the ice sheets. This resulted in the mass melting of water and formation of water vapour into the atmosphere. Further heating caused the oceans around the equator to release CO2, warming the planet still further, until it reached a tipping point.

The tipping point was the melting of the ice sheets to the point where vast reserves of methane trapped under the planet's huge ice sheets were released. Methane is considered a prodigious greenhouse gas, being 30 times more efficient than CO2 in trapping solar heat. This is what I call runaway greenhouse; the combination of a suite of atmospheric gases and sunlight to instigate massive climate change. Others may call it by another name. But the geological record shows this mass warming event DID occur. Put any name on it that you want, the rose will smell just as sweet.

What now worries scientists is that there are presently billions of tonnes of methane stored under the ice of Canada, Siberia and Alaska, and it would take only a very small shift in atmospheric temperature at the poles to cause mass melting and release of methane, similar to the Jurassic event.

Part of this current warming event is Nature's cycle, and part of it is caused by ourselves. As to where one ends and the other starts, is anybody's guess. I get a bit tired of people saying "its a 11 year solar cycle" or "its all happened before". Well yes it has happened before, the issue is its happening NOW, on a geological timescale far shorter than anything a geologist has seen in the last 3.5 billion years, and what exactly can we do about it?

That's the 64 million dollar question, but my gut tells me that releasing more CO2 into the atmosphere will make the problem worse, not better. Certainly there is NO TIME for adaptation of life to extremely rapid climatic change;- this is the worrying thing for geologists and palaeobiologists the world over.

Yes, CO2 does make vegetation grow faster...to a point. There is a finite concentration above which growth rates do not increase any further. Plenty of scientific papers online you can google to see the linear function of CO2 concentrations vs. growth rate.

The irony is that at the rate we are denuding the planet of its vegetation, it is irrelevant whether more CO2 makes things grow faster. There won't be anything left to grow, and certainly nothing left to temporarily "trap" the CO2 we have already generated.

That'll be an interesting situation.

Thanks for reading