John For what it's worth, every paper that's tried examining roughly uniform solar geoengineering with a carbon cycle model that includes ecosystem response has found that it increases NPP and decreases end-of-century carbon burden compared to models with same anthropogenic emissions but no solar geoengineering.
One model that was run with a nitrogen constraint on a much smaller land ecosystem response. Uncertainties are clearly large. Here's a summary/perspective paper we wrote pointing to the need for more serious research https://www.nature.com/articles/nclimate3376.epdf?author_access_token=LJ7xrnEo6oZoRNRYgu7btNRgN0jAjWel9jnR3ZoTv0NZqUjovChb9EdabCEcR6GuvZkepQXaPwfxVdn3_EQ1onk9bPWOsX7ETCUW7OvjKbM7syCkanNFs4sG07XAXjcx See table in supplementary material: https://images.nature.com/original/nature-assets/nclimate/journal/v7/n9/extref/nclimate3376-s1.pdf Interested to hear your take on these papers. I completely agree that priority should be given to reducing emissions. If I was asked allocate a total budget for all action related to climate I would put most of it to net emissions reductions (including carbon removal in the near term if it happens to be more cost or environmental effective than mitigation) , some of the remaining to adaptation, and a small fraction to research on technologies that might be useful in the future including primarily low carbon energy technologies but also carbon removal and solar geoengineering. Yours, David From: John Harte [mailto:[email protected]] Sent: Sunday, December 3, 2017 12:09 PM To: [email protected] Cc: Michael Hayes <[email protected]>; geoengineering <[email protected]>; Keith, David <[email protected]> Subject: Re: [geo] Scientists Look to Bali Volcano for Clues to Curb Climate Change - Scientific American I agree with you, Peter, about unintended and difficult to foresee consequences of SRM. I am particularly concerned about what solar dimming might do to global photosynthesis and thus to the carbon cycle. Each current year, about 5 Gt(C) are sequestered by nature (we emit, 10 each year and we end up at the end of the year with +5). A portion of that sink is the result of photosynthesis very slightly exceeding respiration. A small decrease in photosynthesis can cause a large percent change in the natural carbon sink. This could be critical. Even though the natural sinks will clog over time, I very much doubt that engineered carbon sinks could affordably match what nature currently does, and will continue to do for a while, for free. Our highest priorities should be saving our natural carbon sinks (e.g., with forest protection, and promotion of carbon storing agricultural and grazing practices) and weaning off of fossil fuels asap with renewable clean energy. Preventing ocean acidification will help maintain the integrity of the ocean sink. John Harte Professor of Ecosystem Sciences ERG/ESPM 310 Barrows Hall University of California Berkeley, CA 94720 USA [email protected]<mailto:[email protected]> On Dec 3, 2017, at 1:47 AM, Peter Eisenberger <[email protected]<mailto:[email protected]>> wrote: Vocanic euptions have impacts that are much more imporant than their transitory impact on climate. Their most significant role is in replenishing critcal elements to preserve the fertiliity of the soil. This in turn of course raises the issue of what the impact will be of human efforts to do SRM on the rest of the ecosystems. This in turn is the cause for concern about unexpected consequences and a concern that cannot be addressed by theory or experiment because complex systems evolution is not predictable and we only have one planet. The important aspect of climate change from a risk perspective is not the first order linear responses but rather whether one crosses some tipping point where the internal feedbacks drive the system to a very different and usually catastrophic state. Such tipping points are an inherent property of both the climate and the ecosystems and ala the butterfly effect are inherently unpredictable. Thus the real issue is not how SRM is like volcanoes but rather what are the unintended feedback from SRM. As a physicist ,and not a DAC advocate, the fact is that DAC with permanent storage is the path to address the risk of catastrophic climate change that has the lowest risk of triggering adverse impacts compared to alternatives when implemented at a global scale for any signiifcant period of time. It is clear to that all of us share the goal of wanting to prevent the consequences of catastrophic climate change. So in the positive spirit of tryimg to develop a consencus ageneda I assert The BEST path to address the threat of catastrophic climate change involves DAC with permeant storage -it is necessary . I respectfully ask for resposes to this assertion and that we have a constructive dialoque to see if if stands up to scrutiny. I do not want to be asserting an incorect postion but I do want our community to develop a clear science based consencus for the best actions to take. Again to be clear I personally support R&D on SRM but in the context that DAC with permanent storage is the clear priority. If my assertion is wrong and in fact we have no low risk and cost path to addressing the risk than of course SRM would have a high priority and I would want us to be asserting that . On Sat, Dec 2, 2017 at 11:10 AM, Michael Hayes <[email protected]<mailto:[email protected]>> wrote: Sentinel-SP5 feed: http://m.esa.int/spaceinimages/Images/2017/12/Sentinel-5P_captures_Bali_volcanic_eruption<https://urldefense.proofpoint.com/v2/url?u=http-3A__m.esa.int_spaceinimages_Images_2017_12_Sentinel-2D5P-5Fcaptures-5FBali-5Fvolcanic-5Feruption&d=DwMFAg&c=WO-RGvefibhHBZq3fL85hQ&r=neh3HfyxmZ_gBZatRfRYBzMg9NX5Zr0ZXsotkfaB-qc&m=TDr7cYARkzP5kH883lXYwbybRTKBtMsI21wXZDWgsoA&s=8FU8Vdr_QNDspMFvlkd0yr5LN-XFH3dbA8z5j1y9078&e=> -- You received this message because you are subscribed to the Google Groups "geoengineering" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]<mailto:geoengineering%[email protected]>. To post to this group, send email to [email protected]<mailto:[email protected]>. 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