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Please don't answer without citing scientific research which has a general consensus or article from a reputable source based on verifiable research citations.

I recently read this article about a 2017 PNAS study from Griscom et al (link below) that "estimated natural carbon solutions (NCS) (essentially ecosystem regeneration) have the potential to provide up to 37 percent of the CO2 mitigation that we'd need through 2030, for a 66 percent chance of holding warming to below 2°C."

More specifically, what is the most cost-effective solution? Most geoengineering solutions have significant risks or unknowns which greatly reduce their benefit. Reducing fossil fuel use immediately will reduce short-term economic output with replacing with renewables and alternatives. Maybe simply paying drivers incentives to use alternative vehicles is most-cost effective, as transportation is the largest percentage of greenhouse gas emissions in the US (EPA).

So what is the most cost-effective and how much money would it take to get it done? Global energy-related CO2 emissions were 33.1 Gt CO2 in 2018 according the [IEA report][6]. Apparently from the Griscom study, 10 USD MgCO2e−1 is the "current cost of emission reduction efforts underway and current prices on existing carbon markets" from 2017. 1Gt = 1Pg = 1000Mt = 1000Tg = 10^9 tonnes metric, and 1Mg = 1 tonne, so our CO2 emissions cost us 10*10^9 or 10 billion USD per year. For reference, global GDP is at US$84.84 trillion for 2018, meaning reducing our entire emissions to zero would cost all of 0.0001% of global GDP.

As as corollary, if all benefits of NCS to uncalculated ecosystem services were included, would they be the most cost-effective, and what is the average ROI on research investment to calculate them?

To the Mods: I've changed the title to match the narrow question specified in the body of the question. I've provided an answer that is very specific using calculated figures from cited references. What else would you like to make the question more narrow?

Griscom et al, https://www.pnas.org/content/114/44/11645

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    $\begingroup$ The first step in getting out of a hole is to stop digging. $\endgroup$ – Spencer Sep 22 '19 at 22:54
  • $\begingroup$ Stop burning fossil fuels? $\endgroup$ – Gimelist Sep 23 '19 at 3:34
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    $\begingroup$ Best by what metric and towards what goal, minimizing loss of life, economic disruption, total cost., minimizing temprature increase, reversing increase, not causing the collapse f civilization. You need ot be very precise about what defines "best" in such a question, The answer will include many different things. $\endgroup$ – John Sep 23 '19 at 3:38
  • $\begingroup$ @John, it is a somewhat open question, but guided by the consensus goal to keep global warming below 2°C. This will encompass many of the secondary effects. I realize the utility of a shotgun approach, but I'm looking for the most cost-effective solution based on current science. $\endgroup$ – alchemy Sep 23 '19 at 4:25
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    $\begingroup$ You need to specify just what your criteria for 'best' are. For instance, a moderate-sized nuclear exchange might be effective, and would certainly be quick, but most of us would not appreciate the side effects. $\endgroup$ – jamesqf Sep 23 '19 at 19:12
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We are not going to hold warming below 2 degree C. We might as well stop mentioning that figure.

The idea with the least resistance from the financial market sector (this sector depends upon the idea of growth to sell and trade product) is recapture of carbon or some other idea to cool the atmosphere like the plan Bill Gates was investigating, sending multiple! jet missions up to spray chemicals under the idea of cooling the atmosphere.

I don’t know exactly what Spencer meant by stop digging, and I don’t want to put words in his mouth. For me, it means we must take into account the 2nd Law of Thermodynamics as we devise our solutions for recapture, and other ideas. Everything must be super, super efficient. Of course, the 2nd law is still there, but super efficiency is relatively better. We certainly don’t need to be building sea walls on top of sea walls in a losing battle. It’s better just to move. Multiple, multiple, jet aircraft missions are also highly questionable, at least at first look.

As far as I know (and this is taxing my old brain) but the 1972 Club of Rome-MIT report (not exactly about Climate change per se) was one of the few studies to de facto take into account the 2nd Law.

We find ourselves doing more and more work, and creating more “chaos” to maintain, for instance, the fiction of our financial markets for never-ending growth. More work even just to maintain a certain equilibrium. We are digging ourselves deeper and deeper into a hole to stay even, much less grow.

It is hard to over-emphasize the sheer brute power of the financial market sector. You could almost say that the world military power exists to maintain this sector, and this sector lives in the future. A bond trader goes to work, he works 30 years ahead of us, or more. This sector craves predictability, and the idea seems to be spew the CO2 and other climate gases, and recapture or some other such scheme. I think we need to realize these schemes are taxed by the 2nd Law.

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  • $\begingroup$ Gordon thanks for contributing. Could you add some cost figures to the Gates plan, including risks if possible? That seems like a only a temporary strategy. He's also investing in carbon capture, but it seems like some of the solutions I cited are cheaper. And yes the Limits To Growth was seminal, the reaction to it undismissible, and the 30 year follow up valuable to global modeling. The 2nd law is crucial, and I think that's why the PD study separates reduction by costs and savings. If these are equivalent, it looks like Solar Farms are the most cost-effective. $\endgroup$ – alchemy Sep 24 '19 at 17:02
  • $\begingroup$ Edit: that's Solar Water not Solar Farms (which speaks to your point).. Yes, Maxwell's demon is a bugger, but Peltier and heat exchange devices are getting better, and are even in BMWs and Teslas now. What are some figures on CO2 reduction equivalents from increasing efficiency? It's not the same as switching to renewables, but similar to Managing Refrigerants which could have a massive effect on CO2 equivalents reduction. The technology could also then be used to increase the amount of solar energy captured in the infrared spectrum. $\endgroup$ – alchemy Sep 24 '19 at 17:17
  • $\begingroup$ Maybe you can help me figure out the Project Drawdown difference between reductions by costs versus by savings. And their inclusion of negative costs (isn't that the same as savings?). And importantly for comparisons sake, if they are equivalent. I would think so because they are both in USD, but their methodology might be different, with more unknowns or a more complex chain in the savings. I would hope not, but it would be important to know. $\endgroup$ – alchemy Sep 24 '19 at 17:26
  • $\begingroup$ @alchemy you are certainly more advanced than I am on the science, and you are already aware of what I have mentioned. I am going to copy your question and comments and study it more, because I am very interested in this, and I’m trying to get my young nephew interested in such things since he is still in college. Thanks for giving me much food for thought and study. $\endgroup$ – Gordon Sep 24 '19 at 17:54
  • $\begingroup$ I see, I will copy your answer too. $\endgroup$ – Gordon Sep 24 '19 at 18:03
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In researching my question to provide what is known so far I found the following information. I won't accept my own answer unless it gets the most upvotes.

I found this ranked list from 'Project Drawdown' (PD) that states Managing Refrigerants is the number one solution by GT CO2 reduction by total, but with an unknown cost. Offshore wind turbines (OFTs) seems to be the best solution by total reduction. Electric vehicles (EVs) has the highest savings, but with also the highest cost.

Dividing the reduction amount by the savings leads to OVTs at 11.4 GT CO2 reduction per trillion USD a year (GCR/TUY), then Solar Farms (SFs) at 7.35 and EVs at 1.11 for the top three by savings. However, if all are calculated and ranked, the most reduction by savings is Tree Intercropping at 778 and methane digesters small at 137, the most reduction by cost is Nuclear Energy at 18254 and then Solar Water at 2033, but including the costs with negative numbers (not sure what that means) it's Landfill Methane at -1374 and Solar Farms at -458 GCR/TUY.

I'm not sure if they're including the cost of nuclear accidents or waste storage, since waste storage at least in the US has not been reconciled, and may not be fast enough, so using Solar Water at 2.033 GCR/BillionUY, it would cost 16.3 billion USD per year to reduce the CO2 we emit for energy. Based on a single strategy, that's 2.11 dollars per person in the world (7.7 billion) and $12.50 for every person in the developed world (1.3 billion). Is this correct?

In the PD FAQs they state, "Carbon pricing is a policy mechanism to implement solutions and not in itself a solution to global warming. It is the single most impactful policy proposal that would accelerate the adoption of every solution enlisted."

Adding a few other solutions I've found:

  • CO2 recapture in concrete can reduce it's emissions by 40% (it is 8% of global) and also the energy used. https://www.solidiatech.com/
  • Red mud as a carbon sink, using the hydroxides from aluminum smelting because of the high solubility of CO2 in them.
  • Relying on rock weathering from carbonic acid in rain and because "Coccolithophores account for half of the calcium carbonate creation in the ocean", some kind of phytoplankton farms harnessing their "potential for carbon sequestration but also for the production of high value products, such as fatty acids and pigments."
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    $\begingroup$ I was under the impression, managing refrigerants was more about reducing the impact on ozone levels than global warming (climate change). $\endgroup$ – Fred Sep 23 '19 at 6:30
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    $\begingroup$ @Fred, a bit surprising it is top on the list, but CFCs are a potent (1-9k times CO2, PD site) greenhouse gas (14%, Wikipedia Ozone_depletion_and_climate_change). Apparently reducing CFCs and HFCs have lowered warming by 0.2°F of the 1.6°F raise over the last century (from an article citing this paywalled paper nature.com/articles/ngeo1999). $\endgroup$ – alchemy Sep 23 '19 at 13:27

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