From Oregon State University: Climate projections don’t accurately reflect soil carbon release
CORVALLIS, Ore. – A new study concludes that models may be predicting releases of atmospheric carbon dioxide that are either too high or too low, depending on the region, because they don’t adequately reflect variable temperatures that can affect the amount of carbon released from soil.
The study points out that many global models make estimates of greenhouse gas emissions from soils based on “average” projected temperatures. But temperatures vary widely from those averages. That variability, along with complex biological processes, makes the issue far more complicated.
Researchers said that climate projections, in general, don’t effectively incorporate into their calculations a major component of global warming – the enormous amounts of carbon found in dead, decaying organic matter, which represent up to three times the amount of carbon in the Earth’s live vegetation.
The study was just published in the journal Biogeosciences by scientists from the College of Forestry at Oregon State University and other institutions.
“We’ve done a pretty good job of determining how much carbon is getting absorbed by growing trees and vegetation, how much is coming in,” said Mark Harmon, professor and holder of the Richardson Chair in Forest Science at OSU, and one of the world’s leading experts on the effect of decomposition on the Earth’s carbon cycle.
“However, we know much less about how carbon is released to the atmosphere through the process of decomposition, how much is going out,” he said. “This is half of the equation, and there’s just a huge amount we don’t know about it.”
These findings don’t change the fact that atmospheric carbon dioxide and other greenhouse gas levels are increasing and global warming is a reality, Harmon said. But they do suggest that some of the projections, particularly those made by older models that incorporate even less variability into their analysis, may be flawed.
“This work is important because it brings attention to a component of climate change that was often ignored in the past,” said Carlos Sierra, previously an OSU doctoral student, lead author on the study and now a researcher with the Max-Planck-Institute for Biogeochemistry in Germany. “We can make better projections if we add changes in temperature variability to the equation.”
Researchers have understood, and have been concerned for some time, that warmer temperatures will speed up the rate of decomposition of stored organic matter in soils, a process that ordinarily is slow. This faster rate of decomposition, in turn, could further increase carbon released to the atmosphere and cause even greater global warming.
“This feedback loop is one of our biggest worries with global warming, simply because the amount of carbon stored in soil is so huge,” Harmon said. “Increased release of that soil carbon could offset much of what we’re trying to accomplish with increased growth of live vegetation in forests. And this is a special concern in northern latitudes.”
In the past, estimates of that process were usually based on average temperature increases that were expected, Harmon said. But in the real world, temperatures vary greatly, from day to night, season to season, through heat waves and cold spells. And that variability, researchers say, changes the biological equation considerably and can make averages misleading.
“If the response of soil respiration to temperature was a straight line, then temperature variability would not be important,” Harmon said. “However, the response is curved, which means that as temperature variability increases, so does the average response. This general phenomenon is known as Jensen’s inequality, but it had not previously been applied to soil respiration.”
In simple terms, less variability will equate to less soil carbon release. In the new analysis, considering the effects of variability, scientists found that temperature variability may be reduced in northern latitudes, in particular, and result in carbon releases that are lower than have been projected in one of the areas of the world where this phenomenon is of greatest concern.
The research was not able to precisely quantify this phenomenon and more work needs to be done in that area, the researchers said.
The study reports that:
- The amount of carbon stored in soils worldwide exceeds the amount of carbon in the atmosphere by a factor of two to three.
- There is concern that a large portion of this carbon will be released to the atmosphere as global average temperatures increase.
- Too little attention has been paid to the effect of temperature variability in this process.
- In high latitudes of the Northern Hemisphere, temperature variability is expected to decrease, and release of soil carbon will probably be lower than that predicted by changes in average temperature.
- At lower latitudes, where both average temperature and variability are expected to increase, the release of soil carbon will probably be higher than that predicted by changes in average temperature.
“The findings of this study can greatly modify past predictions about the effects of future average temperatures on ecosystem respiration,” the scientists wrote in their conclusion. “Changes in both temperature and precipitation variance would likely produce complex behaviors not incorporated in current model predictions.”
The research was done by scientists from OSU, the U.S. Geological Survey, and the National Ecological Observatory Network. The study used data from the Long Term Ecological Network Program of the National Science Foundation.
http://oregonstate.edu/ua/ncs/archives/2011/jun/climate-projections-don%E2%80%99t-accurately-reflect-soil-carbon-release
Discover more from Watts Up With That?
Subscribe to get the latest posts sent to your email.
Another shocker…….. you mean our models aren’t correct? That’s just crazy talk!
Wouldn’t humidity also impact how fast CO2 is released from the soil?
The models also do a pretty poor job of estimating such humidity changes.
It’s worse than we thought…..soil positive feedback.
It looks like the overall up take of carbon should increase on a global basis with rising temperatures. More proof that negative feed-backs dominate the climate system!
It seems to me this is another model failure that is being used to scare monger again. There are some huge questions here. Why does warmer temps lead to the release of more soils carbon as is assumed here? Warmer temps would also lead to more biomass.
Why is the estimate that soils contain 3X as much carbon as the atmosphere of any great concern? This has been taught in science classes for years. For example:http://atmo.tamu.edu/class/atmo629/Summer_2008/Week%203/W3.L1.CarbonCycle.pdf
Note that the seas carry 60X the amount of soluble and organic carbon.
Let’s see – how could we prevent all of that wood from decaying and releasing CO2 into the environment?
I know – we could turn the wood into pulp and bury the newsprint in landfills, under a clay cap where it won’t decay for millenia!
😉
Good point, Adrian. If the overall biomass is increasing with increasing CO2 and temp levels, then so will the amount held in soils.
And again we note the conflation of “carbon” and “carbon dioxide”. Seems like an important distinction to make with respect to soils.
A complete and total non-starter…
It might be more over here, and less over there, might be the same, might be less, might be more……
But we understand it all……
NOAA understands and predicts changes in the Earth’s environment, from the depths of the ocean to the surface of the sun
I believe it was Dyson who theorized that the act of tilling the soil (i.e. agriculture) could be a significant contributor to CO2 release.
It’s an interesting little mental exercise to re-spin the article from the (correct) POV that atmospheric CO2 increase is beneficial. E.g., deploring the lock-up of this valuable resource in rotting soil buildup, etc. Heh.
Enlightenment! Warmer temperatures increase atmospheric CO2 by enabling the sub-soil biosphere to thrive. This speeds the conversion of nutrients, which will promote plant growth.
I’ve generally considered the change in CO2 concentration over time as a proxy for the health of the biosphere. As the temperatures warmed and the ice receded, plants and animals gradually expanded their range. More life above & below ground meant more CO2 floating about in the atmosphere. As the temperatures cooled into an ice age, the biosphere struggled to hang on, as do the heightened CO2 levels.
The more we find out – the reality of the less we know becomes glaringly apparent. And we are going to cause massive disruption and death based upon our growing ignorance?
I love the a** covering statement:
“These findings don’t change the fact that atmospheric carbon dioxide and other greenhouse gas levels are increasing and global warming is a reality, Harmon said.”
Gee, correlation equals causation then, science settled … hack …
The amount CO2 in the atmosphere is unimportant, so who cares about the rate at which it is released?
And faster rotting is caused by more life forms eating, which in turn feeds more life in the woods. We can’t have an increase in ecological activity, now can we? It’s unheard of!
Use fungicide between the Tropics of Cancer and Capricorn…. Our CO2 problem should be solved in a few weeks. /sarc
C’mon, these folks are supposed to be Soil Ph.D.’s? I’m just a little ole’ MS Agriculture that’s never used the degree and I know better…
They don’t mention soil pH, alkalinity, carbon to nitrogen ratio’s of the litter etc. which dramatically affect CO2 release whilst the little fungi and bacteria work on the litter, variability of moisture rates during the frost free periods, north slope v. south slope, valley, etc.
How do we get peat bogs? Easy – The rate of herbaceous growth and deposition outpaces the rate of decay.
Is this strictly due to temperature limits in the high latitudes? No. There are bogs in East Texas. There are floating bogs in South Louisiana.
The limiting factors can also include extremes of pH, salinity, nitrogen, oxygen (plants uptake O2 through the roots, which may be in an anaerobic substrate)
Via the roots in the anoxic root zone, the plants in question will have adaptations to “pump” O2 to the roots from the aerial portions of the plant. In this situation there is often a very active biological zone in the substrate in the immediate layer of substate surrounding the root hairs. This zone of biological activity (soil microbes, fungi, etc.) will likely also be oxidizing reduced forms of minerals/elements such as Fe, Mn, Mg, N, S, K, etc. into a form which the plant can use. Beyond this slightly aerobic root zone is an anaerobic muck in which rate of breakdown of organic matter is reduced below that in which aerobic breakdown can occur. If the anaeribic muck is nutrient rich, then the rate of growth and deposition of organic matter can very well exceed the rate of anaerobic breakdown.
In some cases a highly porous subsurface can allow saltwater intrusion into or near rooting zones. But in areas with high “sheetflow” runoff (e.g. S. Louisiana), then the freshwater flows can keep the saline boundary below the root zone. This can have affects on the breakdown of organic matter. If subsidence has occured, which has in S. La. the freshwater marsh essentially becomes a floating marsh… floating over saltwater and absolutely dependent upon continuous influxes of freshwater…. So how about it Army Corp of Engineers? Are there going to be some research projects done to see if there was any benefit to the marshes from your diversion down the strangled Atchafalaya? If (as expected) there were dramatic benefits to the rebuilding of the marshes will you allow more than 30% of the Mississippi’s flow to come that way?
In other words: “We have no bloody idea.”
Tax dollars at work…
Well this is the normal process by which science progresses.
By definition, no scientific theory is exact. So we should always expect deviations from observations. That only means the theory must be refined.
So, again, where is the problem here?
“and more work needs to be done in that area, the researchers said.”
I’ll really believe the first study I see that doesn’t say that.
The point I was trying to make earlier was:
How do you quantify carbon dioxide storage or release, when you have great variability WITHIN a particular biome? The storage and release can change not only horizontally across the biome, but vertically within a particular location. e.g. Did the leaves fall on the soil, or in the bayou?
Humbugs humbled by humus? Humerous!
Well, how did the carbon get there in the first place? The carbon in the soil is deposited by dead vegetation (mostly). New grasses, trees, and other plants grow where the old ones died. The soil exists because the rate of depositon is faster than the rate of decay. Clearly there is more carbon being stored in the soil than coming out. A temperature perturbation might increase the rate of carbon release, but that does not mean the rate is now greater than the carbon capture rate.
It is surely rare that more carbon is released from soil than captured. One example is the San Joaquin Delta. The farmed islands are sinking because the rate of carbon loss is greater than capture. The islands’ soil materials are decaying at a rate that causes their surface elevation to drop by 1/4 to 1/2 of an inch per year. Many are now 10 to 20 feet below sea level.
Note that methane may be released instead of CO2. It depends on the oxic state of the soil, temperature, and whether methanogens and methanotrophs are present and active. Eventually methane is converted to CO2 in the atmosphere.
Plants grow faster when the CO2 concentration is higher. More CO2 can be captured in water and alkalinity increased through biological processes, especially nitrogen fixation.
Is the paper available? If this article sums up the paper correctly, there are gaping holes in it. I have gained more usefull information from one of the comments above than the paper summary.
“However, we know much less about how carbon is released to the atmosphere through the process of decomposition, how much is going out,” he said. “This is half of the equation, and there’s just a huge amount we don’t know about it.”
Is this more modeling? Are they actually taking readings of CO2 released from soil and cataloging the variables? More junk science?
A$ alway$, here’$ the “bottom line” of the re$earch pre$$ relea$e:
“The research was not able to precisely quantify this phenomenon and more work needs to be done in that area, the researchers said.”
$ummary:
taxpayerS –> N$F –> CAGW climate re$earch
Tom T says:
“and more work needs to be done in that area, the researchers said.” I’ll really believe the first study I see that doesn’t say that.
You’ll have a long wait, then, Tom.