Radiocarbon constraints imply reduced carbon uptake by soils during the 21st century | Science

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Karl Thidemann

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Sep 22, 2016, 4:35:48 PM9/22/16
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Thoughts?

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Soil is the largest terrestrial carbon reservoir and may influence the sign and magnitude of carbon cycle–climate feedbacks. Many Earth system models (ESMs) estimate a significant soil carbon sink by 2100, yet the underlying carbon dynamics determining this response have not been systematically tested against observations. We used 14C data from 157 globally distributed soil profiles sampled to 1-meter depth to show that ESMs underestimated the mean age of soil carbon by a factor of more than six (430 ± 50 years versus 3100 ± 1800 years). Consequently, ESMs overestimated the carbon sequestration potential of soils by a factor of nearly two (40 ± 27%). These inconsistencies suggest that ESMs must better represent carbon stabilization processes and the turnover time of slow and passive reservoirs when simulating future atmospheric carbon dioxide dynamics.

http://science.sciencemag.org/content/353/6306/1419

Thomas Goreau

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Sep 22, 2016, 6:37:47 PM9/22/16
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I have not yet had a chance to download and read the paper (I’m on a small island in Indonesia with slow internet), but the abstract makes complete sense, and the authors on this paper are first rate soil scientists.

It is important to realize that a major portion of the long lived soil carbon that is ignored by modelers is in fact black carbon, or biochar, produced by burning. 

Thomas J. F. Goreau, PhD
President, Global Coral Reef Alliance
President, Biorock Technology Inc.
Coordinator, Soil Carbon Alliance
Coordinator, United Nations Commission on Sustainable Development Small Island Developing States Partnership in New Sustainable Technologies
37 Pleasant Street, Cambridge, MA 02139

Books:

Geotherapy: Innovative Methods of Soil Fertility Restoration, Carbon Sequestration, and Reversing CO2 Increase

Innovative Methods of Marine Ecosystem Restoration

The Green Disc, New Technologies for a New Future: Innovative Methods for Sustainable Development

No one can change the past, everyone can change the future

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Thomas Goreau

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Sep 22, 2016, 7:35:37 PM9/22/16
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I’ve now downloaded the paper. Their arguments are also highly model dependent, but they suggest that most of what for some reason they call Earth System Models (“ESM") underestimate soil carbon age in comparison to measured C-14 soil carbon ages. Since ESMs don’t predict soil age, a lot of assumptions need to go into modeling C-14 to compare them.

It seems the core of the issue is that ESMs (which vary greatly among themselves as a result of different models and assumed parameters) include a STIMULATION of photosynthesis and carbon storage as a direct increase of CO2 (negative feedback) and an increase of carbon decomposition due to temperature (positive feedback) and the models are formulated in such a way that the negative feedbacks are about four times larger than the positive ones, making soil a net carbon sink. 

I have problems with the claim built into the models that increasing CO2 results in increased photosynthesis in general. That is true only in greenhouses where there is excess water and fertilizers, so that growth is not nutrient limited. 

Under these conditions, pumping CO2 into the greenhouse (or letting dry ice evaporate) will increase photosynthesis because under these artificial conditions the plants can be CO2 limited. But in fact this never occurs in nature, plants are limited by lack of nutrients, water, and light, and so do not respond to increased CO2, which is present in excess. 

Furthermore, physiological experiments in greenhouses with increased CO2 generally show that plants respond by only taking up enough CO2 to match their nutrient availability, and once they reach the CO2 uptake they can use immediately they close their stomata and stop taking up CO2 entirely! This is a fundamental water conservation mechanism because plants lose thousands of molecules of water for every molecule of CO2 they take up. The climate benefit is that increased CO2 makes plants more efficient in water use, not that they grow faster!

Thomas J. F. Goreau, PhD
President, Global Coral Reef Alliance
President, Biorock Technology Inc.
Coordinator, Soil Carbon Alliance
Coordinator, United Nations Commission on Sustainable Development Small Island Developing States Partnership in New Sustainable Technologies
37 Pleasant Street, Cambridge, MA 02139

Books:

Geotherapy: Innovative Methods of Soil Fertility Restoration, Carbon Sequestration, and Reversing CO2 Increase

Innovative Methods of Marine Ecosystem Restoration

The Green Disc, New Technologies for a New Future: Innovative Methods for Sustainable Development

No one can change the past, everyone can change the future

Greg Smith

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Sep 23, 2016, 9:50:44 PM9/23/16
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Thanks, Thomas.

Folks, I'll add to Thomas' caveats that many models predict higher ozone levels, which could also shut down stomata and otherwise alter plant metabolism.

There are so many variables to consider here.

It's been a long time since I read the IPCC's 2001 Third Reassessment, but if I recall correctly:

1.      In that Reassessment, the IPCC relied primarily scenarios run through two Global Circulation Models -- the Hadley Center's (Britain) and the Canadian Climate Center's (Um.... Canada).

2.      The CCC modelers predicted that much of the southeast's forests would convert to grassland savannah, and areas in the the U.S.' southern central plains could experience temps 14 degrees above the historic norms at that time, with soil moisture content     plummeting by 60 percent. 

3.      The model's did little or nothing to build in major positive feedback loops, and

4.      In assessing impacts, the IPCC assumed atmospheric CO2 levels would not exceed double pre-industrial levels.

It's important to remember that the IPCC reassessment are consensus documents, meaning every member nation may chew on the drafts.

What's not quite said is often more serious than what does get said, and what's said is more than scary enough.


Best,

Greg

 

At 07:35 PM 9/22/2016, you wrote:
I’ve now downloaded the paper. Their arguments are also highly model dependent, but they suggest that most of what for some reason they call Earth System Models (“ESM") underestimate soil carbon age in comparison to measured C-14 soil carbon ages. Since ESMs don’t predict soil age, a lot of assumptions need to go into modeling C-14 to compare them.


It seems the core of the issue is that ESMs (which vary greatly among themselves as a result of different models and assumed parameters) include a STIMULATION of photosynthesis and carbon storage as a direct increase of CO2 (negative feedback) and an increase of carbon decomposition due to temperature (positive feedback) and the models are formulated in such a way that the negative feedbacks are about four times larger than the positive ones, making soil a net carbon sink.

I have problems with the claim built into the models that increasing CO2 results in increased photosynthesis in general. That is true only in greenhouses where there is excess water and fertilizers, so that growth is not nutrient limited.

Under these conditions, pumping CO2 into the greenhouse (or letting dry ice evaporate) will increase photosynthesis because under these artificial conditions the plants can be CO2 limited. But in fact this never occurs in nature, plants are limited by lack of nutrients, water, and light, and so do not respond to increased CO2, which is present in excess.

Furthermore, physiological experiments in greenhouses with increased CO2 generally show that plants respond by only taking up enough CO2 to match their nutrient availability, and once they reach the CO2 uptake they can use immediately they close their stomata and stop taking up CO2 entirely! This is a fundamental water conservation mechanism because plants lose thousands of molecules of water for every molecule of CO2 they take up. The climate benefit is that increased CO2 makes plants more efficient in water use, not that they grow faster!

Thomas J. F. Goreau, PhD
President, Global Coral Reef Alliance
President, Biorock Technology Inc.
Coordinator, Soil Carbon Alliance
Coordinator, United Nations Commission on Sustainable Development Small Island Developing States Partnership in New Sustainable Technologies
37 Pleasant Street, Cambridge, MA 02139
gor...@bestweb.net
www.globalcoral.org
Skype: tomgoreau
Tel: (1) 617-864-4226

Books:

Geotherapy: Innovative Methods of Soil Fertility Restoration, Carbon Sequestration, and Reversing CO2 Increase
 http://www.crcpress.com/product/isbn/9781466595392

Innovative Methods of Marine Ecosystem Restoration
http://www.crcpress.com/product/isbn/9781466557734

The Green Disc, New Technologies for a New Future: Innovative Methods for Sustainable Development
 http://www.greenthindisc.org

No one can change the past, everyone can change the future

On Sep 22, 2016, at 6:37 PM, Thomas Goreau <gor...@bestweb.net> wrote:

I have not yet had a chance to download and read the paper (I’m on a small island in Indonesia with slow internet), but the abstract makes complete sense, and the authors on this paper are first rate soil scientists.


It is important to realize that a major portion of the long lived soil carbon that is ignored by modelers is in fact black carbon, or biochar, produced by burning.

Thomas J. F. Goreau, PhD
President, Global Coral Reef Alliance
President, Biorock Technology Inc.
Coordinator, Soil Carbon Alliance
Coordinator, United Nations Commission on Sustainable Development Small Island Developing States Partnership in New Sustainable Technologies
37 Pleasant Street, Cambridge, MA 02139
gor...@bestweb.net
www.globalcoral.org
Skype: tomgoreau
Tel: (1) 617-864-4226

Books:

Geotherapy: Innovative Methods of Soil Fertility Restoration, Carbon Sequestration, and Reversing CO2 Increase
 http://www.crcpress.com/product/isbn/9781466595392

Innovative Methods of Marine Ecosystem Restoration
http://www.crcpress.com/product/isbn/9781466557734

The Green Disc, New Technologies for a New Future: Innovative Methods for Sustainable Development
 http://www.greenthindisc.org

No one can change the past, everyone can change the future

On Sep 22, 2016, at 4:35 PM, Karl Thidemann <karl.th...@gmail.com > wrote:

Thoughts?

---

Soil is the largest terrestrial carbon reservoir and may influence the sign and magnitude of carbon cycle–“climate feedbacks. Many Earth system models (ESMs) estimate a significant soil carbon sink by 2100, yet the underlying carbon dynamics determining this response have not been systematically tested against observations. We used 14C data from 157 globally distributed soil profiles sampled to 1-meter depth to show that ESMs underestimated the mean age of soil carbon by a factor of more than six (430 ± 50 years versus 3100 ± 1800 years). Consequently, ESMs overestimated the carbon sequestration potential of soils by a factor of nearly two (40 ± 27%). These inconsistencies suggest that ESMs must better represent carbon stabilization processes and the turnover time of slow and passive reservoirs when simulating future atmospheric carbon dioxide dynamics.


http://science.sciencemag.org/content/353/6306/1419

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Thomas Goreau

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Sep 24, 2016, 4:53:15 AM9/24/16
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Frankly these biomass/climate change models are such a poor description of plant physiology that it is amazing that they are extrapolated way beyond any range in which they might be quasi-valid. There is an element of faith in the accuracy of these models in future predictions that is more like religion than science: If it’s so complicated very few people can understand it, and consumes a great deal of money, it must be true, right?

But there is an even more important point missing in this paper. They use the radiocarbon ages of soil, but don’t really distinguish between the black carbon (high temperature biochar) component that lasts essentially forever in soils, and the other shorter lived fractions. If we were to significantly increase the biochar component of soils, then their carbon sequestration capacity could be greatly increased. 

Thomas J. F. Goreau, PhD
President, Global Coral Reef Alliance
President, Biorock Technology Inc.
Coordinator, Soil Carbon Alliance
Coordinator, United Nations Commission on Sustainable Development Small Island Developing States Partnership in New Sustainable Technologies
37 Pleasant Street, Cambridge, MA 02139

Books:

Geotherapy: Innovative Methods of Soil Fertility Restoration, Carbon Sequestration, and Reversing CO2 Increase

Innovative Methods of Marine Ecosystem Restoration

The Green Disc, New Technologies for a New Future: Innovative Methods for Sustainable Development

No one can change the past, everyone can change the future

Tod Wickersham

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Sep 26, 2016, 5:14:46 PM9/26/16
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Tom et al,

 

Thank you for your review and comments.

 

Dr. Marcia DeLonge from Union of Concerned Scientists blog post also provides excellent context for this study.

 http://blog.ucsusa.org/marcia-delonge/soil-carbon-cant-fix-climate-change-by-itself-but-it-needs-to-be-part-of-the-solution

 

Best,

 

Tod

 

Theodore "Tod" S. Wickersham, Jr., President
Beneficial Results LLC
Tod.Wic...@BeneficialResults.com | @TodWickersham
Washington: 202-322-2267,  Austin: 512-680-4379
www.BeneficialResults.com | @BeneResults | FB

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