Carbon-Emitting Soil Could Speed Global Warming, Warns 26-Year Study (theguardian.com)

An anonymous reader quote the Guardian: Warming soil releases more carbon into the atmosphere than previously thought, suggesting a potentially disastrous feedback mechanism whereby increases in global temperatures will trigger massive new carbon releases in a cycle that may be impossible to break... The 26-year study is one of the biggest of its kind, and is a groundbreaking addition to our scant knowledge of exactly how warming will affect natural systems. Potential feedback loops, or tipping points, have long been suspected to exist by scientists, and there is some evidence for them in the geological record. What appears to happen is that once warming reaches a certain point, these natural biological factors kick in and can lead to a runaway, and potentially unstoppable, increase in warming...

In the Science study, researchers examined plots of soil in the Harvard Forest in Massachusetts, a mixed hardwood forest in the U.S. They experimented by heating some of the plots with underground cables to 5C above normal levels, leaving others as a control. The long-term study revealed that in the first 10 years there was a strong increase in the carbon released from the heated plots, then a period of about seven years when the carbon release abated. But after this second calmer period, which the scientists attribute to the adjustment of the soil microbes to the warmer conditions, the release of carbon resumed its upward path. From 1991, when the experiment began, the plots subjected to 5C warming lost about 17% of the carbon that had been stored in the top 60cm of the soil, where the greatest concentration of organic matter is to be found...
Lead scientist Jerry Melillo, points out that currently 10 billion metric tons of carbon gets released into the atmosphere every year, but "The world's soils contain about 3,500 billion tons of carbon. If a significant amount of that is added to the atmosphere, due to microbial activity, that will accelerate the global warming process. Once this self-reinforcing feedback begins, there is no easy way to turn it off. There is no switch to flip."

Comments

Ecology Always Wins

[Jzanu]

Global warming effects the habitability of every region for every organism, bacterial included. Before denialists complain on economic costs they must recognize the second layer of economics impacts from damage to the base agrarian sector that powers all of the economy. Humans require food to live, to use and to make everything else. We face quick changes that disrupt our existing transportation and market networks that distribute these resources, as well reduction in total yields. That damage and the cost of that damage dwarf all complaints about the costs of responding, through limits and changes in production techniques, and through transition to alternative sources of fuels and electricity.

Re:Ecology Always Wins

[Jzanu]

There is nothing arable about previously frozen dirt. It will take decades for it to become fertile from the repeated decay of generations of migrating organisms.

Re:Ecology Always Wins

[Anonymous Coward]

Then how is there oil in the Arctic?

Answer: Once upon a time, there was plenty of life in the north. Then it died. Some of it became oil, the rest of it is nutrients in the dirt.

Unless you it is your contention there was once life not made out of nutrients?

Yet another trumpbot

[Anonymous Coward]

> The sun's total energy that hits the planet Earth surface is 174 000 Terawats of heat energy every year. Humanity generates only about 25 Terawatts of enegy annually [...]

Warming is about the retention of (some fraction of) those 174 petawatt (no I didn't check the numbers), not about a bit more or less of those 25 terawatt (no, I didn't check the numbers).

You stupid, drooling trumpbot.

Re:Global warming and global cooling happen every

[allcoolnameswheretak]

You are confusing energy with CO2 concentration in the atmosphere.

If your numbers are correct, the point is not the relative energy generation of humans vs the sun, but that due to the higher CO2 concentration caused by humans, more of those 174 000 Terawats of heat energy from the sun that you mention will be retained in the atmosphere.

Re:So is the situation dire enough to

[blindseer]

Ah, I see. You'd rather people die than use nuclear power. All you said was a repeat of what you said before, that nuclear power costs too much so we should all die instead.

I got it. We're done here.

Gaia always wins

[Latent Heat]

The Carbon Cycle is well understood. Of the CO2 emitted by human activity, half of that ends up in the atmosphere, the other half ends up in sinks. Half of that half goes into the ocean and the remaining half of that half goes into the soil.

The reservoir capacity of the ocean is vast, orders of magnitude greater than the atmosphere. What prevents all of the CO2 from diffusing into the ocean is 1) the equilibrium of atmospheric and ocean CO2 follows a non-linear roughly 10th-power relationship owing to the chain of chemical reactions by which CO2 is "dissolved" (rather chemically bonded into soluble carbonates) and 2) there is a finite rate of mixing of the surface ocean layer with the deep layer. This model of the ocean along with some assumptions regarding the cycling of carbon between the atmosphere and the soils on land gives an accurate trace of the increase in atmospheric CO2 concentration from about 290 ppm at the dawn of the Industrial Revolution to over 400 ppm today. It also predicts the carbon isotope concentrations along with the seemingly short lifetime of CO2 in the atmosphere from the rapid extinction of radioactive C14 from atmospheric H-bomb testing that (mostly) ended in the mid 1960s -- this has to do with the non-linear absorption of CO2 by the ocean, which exchanges CO2 molecules at a high rate but resists requires greater changes in atmospheric partial pressure of CO2 to shift the chemical equilibrium. This may seem counter to intuition, but this is well understood P-Chem.

Even though only half of the CO2 emitted by humans ends up in the atmosphere on account of the sinks, just about all of the increase in CO2 is the fault of humans. That is, unless there is a natural source of thermally stimulated emission of CO2 that needs to be taken into account.

It is perhaps not widely known, but there is a large fluctuation in the year-to-year increase in atmospheric CO2. The fluctuation is of comparable magnitude as the human contribution that is believed to be much more steady -- we have boom and bust cycles in industrial output, but the variations are not quite that much.

You may not have heard of this fluctuation, but NOAA's Carbon Cycle Guru Pieter Tans certainly knows about it. He attributes it to the effect of temperature changes on the rotting of fallen leaves and other litter in the tropical rainforests. He claims that the leaves that fall are very quickly rotted away, releasing most of their carbon back as CO2 into the atmosphere. His claim is that owing to the rapid decay of dead plant matter under tropical conditions, the reservoir is small. It accounts for the correlation between temperature and increase in atmospheric CO2 (called "net emissions), only occurring over short time windows. This correlation exists over longer time scales, but matters get fuzzy because human CO2 has ramped up over a time of gradual warming.

Were you to believe Pieter Tans (yes, believe as much of this is based on modeling assumptions), there is minimal effect of decades-long increase in atmospheric temperature in driving CO2 emissions from the soil -- the decades-long increase is all attributed to the decades long gradual increase in industrial emissions with minimal contribution from warming of soils. Were you to regard NOAA's top Carbon Cycle dude as wrong, that increasing temperature drives a positive feedback of CO2 emissions over longer times than the year-to-year fluctuations seen in the atmospheric CO2 "Keeling curve", which TFA does, you would have already seen the effect on atmospheric CO2 because the climate has indeed been warming for most of the 20th century -- it has been warming, has it not, that is, unless you are a Climate Change Denier?

If contra-Pieter Tans Head of the Carbon Cycle Section at NOAA the long term temperature trend is stimulating CO2 emissions from the soil in a positive feedback, there must be a countervailing negative feedback in the form of a commensurately higher absorption of CO2 by plants, an absorption that is sens

Re:Wow, that's a long term study

[GameboyRMH]

Here you go. Took a couple minutes searching:

https://www.skepticalscience.c...

http://www.easterbrook.ca/stev...

Will you stop lying now?

Re:Histrionics

[GameboyRMH]

Absolutely wrong, where did you learn this nonsense? We aren't crawling up anything that could appear to be a natural spike, we've made our own spike in what should be a trough:

https://www.skepticalscience.c...

The earth should be cooling now, if there were no anthropogenic climate effects.