Sensitivity of atmospheric CO2 growth rate to observed changes in terrestrial water storage

[Andrew Lockley]

Poster's note: vital for integration of CDR and SRM 

https://www.nature.com/articles/s41586-018-0424-4

Sensitivity of atmospheric CO2 growth rate to observed changes in terrestrial water storage

• Vincent Humphrey, 
• Jakob Zscheischler, 
• […]
• Sonia I. Seneviratne 

Naturevolume 560, pages628–631 (2018) | Download Citation

Abstract

Land ecosystems absorb on average 30 per cent of anthropogenic carbon dioxide (CO2) emissions, thereby slowing the increase of CO2 concentration in the atmosphere1. Year-to-year variations in the atmospheric CO2growth rate are mostly due to fluctuating carbon uptake by land ecosystems1. The sensitivity of these fluctuations to changes in tropical temperature has been well documented2,3,4,5,6, but identifying the role of global water availability has proved to be elusive. So far, the only usable proxies for water availability have been time-lagged precipitation anomalies and drought indices3,4,5, owing to a lack of direct observations. Here, we use recent observations of terrestrial water storage changes derived from satellite gravimetry7 to investigate terrestrial water effects on carbon cycle variability at global to regional scales. We show that the CO2 growth rate is strongly sensitive to observed changes in terrestrial water storage, drier years being associated with faster atmospheric CO2 growth. We demonstrate that this global relationship is independent of known temperature effects and is underestimated in current carbon cycle models. Our results indicate that interannual fluctuations in terrestrial water storage strongly affect the terrestrial carbon sink and highlight the importance of the interactions between the water and carbon cycles.

[Thomas Goreau]

The most effective way to increase soil water storage capacity, and future carbon storage, is to increase it’s soil organic carbon and black carbon (biochar). Each gram of soil carbon holds many grams of water.

Regenerative development to reverse climate change (Geotherapy) strategies should focus on increasing soil carbon to increase carbon storage and soil water, and increase future carbon storage as shown in this recent paper that dry years cause more rapid CO2 buildup in the atmosphere (below). We’ll help solve our food and water supply problems at the same time………..

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...@globalcoral.org
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

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[Brian Cady]

But Dr. Goreau, Isn't this call for soil carbon in direct conflict with agricultural yields of carbon-rich crops? And about it being 'most efficient'; When I think of efficiency, I think of more of some yield with less of some input. What are, or will be, the limiting inputs going into carbon sequestration?

Will it be dollars per ton carbon fixed, or joules of sunlight energy per ton carbon fixed, or human lives per ton?

By the way, I noticed that William H. Schlesinger, in Biogeochemistry: An Analysis of Global Change

agrees with you that calcium carbonate dissolves at ocean depths. It's amazing to me that all the carbonates of earth must have formed on continental shelves; that our atmosphere's CO2 concentration is so dependent on these..

Brian

To view this discussion on the web visit https://groups.google.com/d/msgid/CarbonDioxideRemoval/EBBB014B-C14A-4CB6-BA73-9C1F569C1942%40globalcoral.org.

[Thomas Goreau]

Dear Brian,

Thanks for your comments!

With regard to soil carbon and biomass carbon it is erroneous to regard them as a zero sum game, they go together: more soil carbon results in more water and nutrients in soil and higher biomass, and also all soil organic carbon was previously living biomass. Whether that biomass becomes soil carbon or is burned, respired, or decomposed to CO2 depends on how we manage non-crop biomass carbon. Historically we have managed it to maximize its oxidation to CO2, plundering and wasting our carbon assets instead of reinvesting them in future growth, which we also know how to do, but don’t do on a large enough scale to make a difference. 

By efficiency I meant only carbon storage and recycling efficiency. Carbon quantity itself is an excellent metric of any carbon pool, especially when multiplied by its lifetime in that pool. But you are right to suggest energy as a qualitative criterion, as the carbon varies so enormously in energy content.

In terms of the ocean, there is a well defined “snow line” on the sea floor above which limestone accumulates, and below which it dissolves. The level of the snow line depends on pH, controlled by the CO2 content (as the major acid in the ocean), and hence by temperature. Since the legacy of the last few million years of Ice Ages is that the deep sea is just above freezing, this makes the snow line over the last few million years very high, so most of the ocean floor can’t accumulate the limestone rain of microscopic shells constantly falling from surface waters. 

In a true hyper thermal event, such as the mass ocean anoxia that took place during the Paleocene-Eocene thermal maximum, deep ocean waters may have been 15-20 C warmer, had much less dissolved oxygen and CO2, thus promoting accumulation of organic carbon in dead zones, and as limestone on the sea floor. That is where we are headed now, but it takes 1500 years for the ocean to turn over, and until that happens, and the deep sea warms up, we won’t feel the real long term impacts of global warming. We won’t see them, but we must ensure that our descendants don’t!

Best wishes,

Tom

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...@globalcoral.org
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

To view this discussion on the web visit https://groups.google.com/d/msgid/CarbonDioxideRemoval/CAAoq7h%2BV%2B0Y_DMz0bPBSNafXdvFN3VN7rRAZJZNB_jfHx-S2JA%40mail.gmail.com.

[John Crusius]

I have not read the Nature article, which looks interesting and its conclusions quite plausible.  However, I do know that the moisture content the article alludes to is measured by satellite gravimetry.  This is not my area of expertise, but satellite gravimetry infers the integrated (g/m2) amount of water in a vertical column of the earth, which I am fairly sure is primarily a measure of the amount of groundwater (height of the water table).  This needed have much direct connection to soil organic carbon content.  Or, considered another way, enhancing surficial soil organic matter content won't be a big driver of the height of the water table.  Am I missing something?

John

To view this discussion on the web visit https://groups.google.com/d/msgid/CarbonDioxideRemoval/EBBB014B-C14A-4CB6-BA73-9C1F569C1942%40globalcoral.org.

[Thomas Goreau]

There are solid connections between soil moisture and groundwater levels. 

Soils with high organic matter hold much more moisture, and allow gradual discharge to the groundwater. 

Water percolation to groundwater is higher where there are deep tree roots. 

Increased evapotranspiration over large forested areas increases rainfall. 

The key is to get more local water recycling via transpiration/rain cycles, and to increase groundwater discharge slowly throughout the year, at the expense of excess surface runoff during high rain events, which causes intensified flooding and drought cycles.

In many deforested areas where perennial springs and rivers had dried up, restoring vegetation has brought the surface water back, it’s astonishing to see brown areas turn green again!

The cover of the Geotherapy book has precisely such a set of before and after photographs of an area in Zimbabwe where regenerative grazing management has increased soil carbon, grasslands, and reinvigorated long dead perennial springs and streams, allowing elephants to spread back  into areas where before they could find no water or grass. 

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...@globalcoral.org
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

To view this discussion on the web visit https://groups.google.com/d/msgid/CarbonDioxideRemoval/CAExHVaTp%2BKsLkCXT0UfXBb_%2B7zxXy%2BPw8C%2Bq1qwBH5aBG6om1w%40mail.gmail.com.