How can a forest be a carbon sink? Trees grow, die, and rot or burn. It is a steady state system unless it is changing in area. Where do they think the sunk carbon is going? Into a Swiss bank account?

The ability of global warming researchers to be oblivious the most basic laws of science is quite remarkable.

"How can a forest be a carbon sink? It is a steady state system unless it is changing in area."

The terrestrial carbon sink most definitely is not a steady state system; the carbon pool fluctuates over time, both upwards and downwards --- equivalently, the carbon fluxes into/out of the vegetation are not constant in time. We can measure this directly (e.g., forest inventories, flux tower measurements) as well as see the gross impact on the interannual variability of global CO2 concentrations.

Change in area is one way in which the size of the carbon pool can change (new growth, fires, deforestation, ...) In addition, the surface area covered by vegetation can remain the same, yet biomass and carbon storage can still change (e.g., trees grow taller or shorter on the same patch of land, or closer or farther together).

There are various processes which control the rate at which forests can source or sink CO2. For instance, when CO2 levels go up, plants grow better and store more carbon: this is the carbon fertilization factor. On the other hand, when temperatures go up, organic decay proceeds faster and releases more stored carbon: this is the heterotrophic respiration factor.

The Earth is a closed system, but that doesn't mean that it is in constant equilibrium.

"The ability of global warming researchers to be oblivious the most basic laws of science is quite remarkable."

A simple Google search on "forest carbon sink" would reveal the basic laws of science of which you are ignorant about. For that matter, you could just read the Nature paper that Brett linked. But I doubt that will cause you to retract or apologize for the above accusation maligning the scientists who study the terrestrial carbon cycle.

"Patrick Henry", one of our leading contrarians observes:
How can a forest be a carbon sink? Trees grow, die, and rot or burn. It is a steady state system unless it is changing in area. Where do they think the sunk carbon is going? Into a Swiss bank account?

The ability of global warming researchers to be oblivious the most basic laws of science is quite remarkable.

I suppose Patrick was doing something else when his fellow contrarians Paul, Darren, and Gary were busy digging themselves into a very deep hole regarding this aspect of the carbon cycle. It's no wonder that NGW Steve needed to distract the thread with his "specific heat" red herring. It would seem that the ranks of those who are "oblivious the most basic laws of science" are not restricted to "global warming researchers."

On the other hand, the ground underneath the forest -- where a sizable portion of the carbon-rich roots and detritus ends up -- is a pretty good "Swiss bank account" for captured atmospheric CO2.

PH,

Tress rot very slowly in the northern forest. The soil can become several feet thick with only partially decayed material.

The sponge like forest floor is acidic due so many coniferous needles. This tends to retard degradation of organic material. Fallen leaves, trees and moss remain on the forest floor for a long time in what is a cool, moist climate. Material can date all the way back to the ice age.

Typically, fires don't occur because it barely drys out during the summer.

Global Warming is nipping at the edges of the boreal forest. Drying it out during the summer to the point that forest fires can occur.

Andrew,

I've done lots of geology field work in northern forests. The soils are very thin, underlain by rock and more or less at equilibrium. In a natural forest, there is steady state between, growth, fire and decay.

Forest fires are a huge problem in the world's largest boreal forest - i.e Siberia. This is due to lumber companies intentionally burning forests to make them legally available to logging.

The idea that forests on a global scale are a significant long term sink is absurd.

Ambitwistor,

Of course you can find local sinks and sources over short periods of time. The point is that on a macro scale, the world's forests are more or less steady state unless they are destroyed.

Well, I am certainly glad to see that bt has found enough time in his busy day to grace us with his imperial presence.

All hail, bt!!

On the other hand, the ground underneath the forest -- where a sizable portion of the carbon-rich roots and detritus ends up -- is a pretty good "Swiss bank account" for captured atmospheric CO2.

Except when said forest catches fire and releases said "Swiss bank account" back into the atmosphere.

Patrick Henry,

Well, that's a pretty weaselly response. The devil is in the details. "More or less steady state" can translate into significant variations in the ability of the terrestrial biosphere to sink carbon during, say, the 21st century, depending on whether it's "more" or "less". The object of carbon cycle research is to quantify the variation.

Simply waving your hands and saying "well the carbon's gotta come back sometime" is not terribly useful, since "how much" and "when" are the crucial questions. Certainly you have not demonstrated that the researchers mentioned here are "oblivious" to the "basic laws" of science. I note that you have not retracted nor apologized for such libelous statements.

Andrew, thanks. Day in and day out you answer people who are not so kind with their comments to you or others with equanimity. (PH, this isn't directed at you.) You give a good example of how to be a gentlemanly scholar. Please keep it up!

Here is another one of them there all believing computor models, so must be true eh.

Ambitwistor,

Classic case of can't see the forest for the trees. During the last century, fire suppression caused a lot of organic matter to accumulate on the forest floor, and an excess of growth. Now it is swinging the other way with huge forest fires clearing out the excess built up over the last 100 years. Arizona and Colorado both had (by far) their largest forest fires on record in this decade, largely due to fire suppression since 1900.

Averaged out over time, there is no reason to believe that forests will be a net sink of carbon. (Unless we cut the trees down intentionally and bury them to sequester the carbon.) Trends like destruction of the rainforests and intentional burning in Siberia certainly point to this being unlikely.

Patrick Henry,

"Averaged out over time, there is no reason to believe that forests will be a net sink of carbon."

You persist in missing the point. "Averaging out over time" is precisely what hides all of the actual variation in carbon sinks. The questions are, HOW MUCH and OVER WHAT TIME PERIOD. If you average for, say, a thousand years, you'll apply a strong enough low pass filter that you've got something approaching "equilibrium". But that's not relevant when considering the question of, say, the effect of the terrestrial carbon cycle on 21st century climate change.

The fact is, there are plenty of evidence that forests both have been and will continue to be a net carbon sink over multidecadal time scales (although, as the article above notes, there is a small possibility that they could become a net carbon source given enough warming.) I listed a number of those reasons above, including both processes and observations. If you bothered to even read the linked article, you'd be aware of the evidence that your claims are wrong.

As I said before: simply waving your hands and saying "well the carbon's gotta come back sometime" is not terribly useful, since "how much" and "when" are the crucial questions. By refusing to recognize quantitative differences, you are begging the question.

WOW, I'm blushing at being included in the BT list.

I'm not worthy, I'm not worthy! LOL

Seriously, we're debating computer models here. It is amazing to me how much reliance is placed upon programming. I know, I know, there are no other realistic ways to project what may have, or could be, happening, but I think all of the models, both for and against aspects of the AGW religion, need to be taken with a grain or two of salt.

Betcha I could come up with a computer model that would show that a pig could fly. Well, actually, I could probably find someone who could write a computer program to show that. As a skeptic, I really can't read or write or feed myself.

Ambitwistor,

I guess this is a difference in philosophy about AGW. I see the year to year measurements of CO2 as being little more than an academic exercise. The long term trends over the next century seem far more interesting and I see the carbon balance in forests over that period as being little more than noise - unless there is aggressive deforestation or harvesting and sequestering of wood.