Have to chime in on praising the clarity in this discussion, particularly for a non-economist, non-policy perspective.

I do have questions though from a technological point of view. Where does increased efficiency fit into this puzzle? There is available technology in building design that can reduce energy consumption significantly. Fair body of demonstrations of the ease of implementation and the reliability of design predictions.

Theoretically in ff based energy grids that translates to carbon reductions. Lots of ifs. Sector dependent. Pretty exhaustive technical knowledge and quality management required. And sounds a lot like the passage that made me weep in gratitude as Dick Fiddler pointed out. The beauty of the technology is that, like so many of the deep technical topics of building design, implementation can be adopted in the design and construction practices without significant disruption or retraining.

If energy efficiency policy, efficacy, modeled impact is discussed in the book, fair enough. It’s going on my shelf regardless.

This conversation is an invaluable primer. Much appreciation to you Mr. Roberts for bringing this marvelous team to the microphone.

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As one who has been working for practical implementation of clean energy programs for over 40 years, the clarity of this interview is inspiring. There is so much jargon/BS/wishful thinking/happy talk in the clean energy field, and it only gets in the way of doing (and funding) the regulatory and incentive programs which actually are capable of getting the job done. Reading a sentence like "To set your additionality standards and baselines and all the technical details about non-observable phenomena, you have to have rich and intricate knowledge. Well, that's also what you need to do to set up a regulatory program." almost makes me weep with gratitude. (By the way, that's very parallel to what's needed for an effective incentive program.) Big thanks to Dave Roberts!

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It's pretty remarkable, after 30 years of experience with offsets, that we're still having first-order conversations about what they are and how they work, with different observers arriving at diametrically opposed conclusions. You can see that just by scanning this year's offset titles at https://2020offsetsbib.climatesites.net

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Notwithstanding the problems with offsets, there is a big push to massively expand the market's scope. https://carbonoffsetsround2.climatesites.net

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crazy idea for a carbon offset; set up rainforest host countries like Brazil, DRC, and or Indonesia with universal incomes funded by the international sale of carbon offsets. Eliminate deforestation in the developing world while avoiding the trope of lecturing people in 3rd world poverty about the environmental consequences of their attempts to feed their families.

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This is close to what the Norwegians have tried to do, and the evaluations of their program have not been hopeful.

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David---Your introductory statement copied below should include the major flaw of offsets: the frequent lack of additionality. "Carbon reductions" via offsets can be very real and still have an adverse impact on emissions. Because many forest reductions would have occurred anyway without offsets, it allows industries to avoid their own reductions so the net impact is that offsets can increase emissions. Verification is just one of the problems.

"But the model only works in practice if the carbon reductions represented by carbon offsets are real — verifiable and verified. Cullenward and Victor argue that they rarely are, and furthermore, that the incentives created by the programs themselves work against reliable verification. Large-scale offsets programs inevitably spark a race to the bottom."

There is a need for assessing the political economy behind offsets (please explore and write more). The growth is accelerating in this perverse policy. BP just bought the biggest offsets broker in California, Carney has a group of major companies lined up, the airlines CORSIA agreement will expand offsets, and brokers, lawyers, forestry consultants, agriculture interests all see a path that is not good for the climate. EDF, IETA and many others are focused on getting the Paris Accord Article 6 rules approved next November at the COP 26 in Scotland. This will give the veneer of legitimacy to this unfortunate trend. It is no surprise that Davos was the initiator of the trillion trees program.

Finally, the real damage from expansion of this policy will be in developing countries. Article 6 rules will be essentially the same as the Kyoto Protocol offsets program which was a failure. Around 85% of the Kyoto offset projects could not demonstrate reduced emissions. The Kyoto offset price sank to 40 cents/ton/CO2 which were grabbed up by EU industries under the EU ETS cap and trade and submitted for compliance.

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PS after a very long day, just wanted to say how much I appreciate what you've written here. There is such a long history on this issue, but every time somebody puts an offset on a blockchain it's like "wow check out this innovation" instead of "have I seen this before?" We have seen this before. And each time we repeat the experiment we get the same result.

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I'll let the good Dr. Volts speak for himself, but I suspect the "verifiable and verified" bit was meant to encompass additionality concerns. We cover all this in the book, including the experience with CDM, how offsets contributed to the 10-year struggle to turn the EU ETS around, and the awful ugliness that is the CORSIA process.

(One of the problems with offsets is all the terminology — and the fact that counterfactual logic with additionality and leakage literally doesn't have a proper verb tense. Turtles all the way down!)

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It's common to assume that "verification" includes assessing additionality, but that's a misunderstanding. There is no way to "verify" a counter-factual baseline - it's basically a policy decision that then has to be taken as a given from then on out.

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What is the quality of the Stripe carbon offset program? Direct air capture seems like it should avoid most of the verification issues.

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Disclosure: my colleagues and I at CarbonPlan (a nonprofit research organization) worked with Stripe on its program.


I think what Stripe is doing is transformative. They are buying quality, permanent carbon removal at any cost. Notably, by breaking the link between price and volume, they can focus on quality without cutting corners. The downsides are (1) high-cost projects don't produce as many tons, and therefore don't allow for neutrality claims on a limited budget, and (2) Stripe has only put $1M into the program so far. We're a long way from a global solution, but this model is capable of scaling promising ideas and doesn't face self-destructive political barriers. Totally different from traditional offsets.

(David and I talk in the book about the need to eliminate public offsets programs and redirect funds through effective public spending programs; Stripe is basically following this approach on the private side and with a focus on permanent carbon removal. You could imagine other approaches focused on other spending priorities. The key is to maximize benefits in an expenditure program, rather than produce a race-to-the-bottom when competing exclusively on marginal costs.)

High-cost projects like direct air capture don't suffer additionality concerns. That's a blessing to accompany the curse of high cost. Reporting and verification is often a little easier with engineered approaches to carbon removal, too, but issues like underground CO2 storage remain complex and can also be controversial.

Bottom line is that measuring CO2 flows in a pipe is easy, and confidence that these flows are new or additional is high because of high project costs. Problem is no one has the budget to go fully carbon neutral on things that are obviously high-quality today.

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Here is a question from a consumer & citizen standpoint:

Is it better if I do nothing or if I try to offset my carbon footprint with a company like Wren https://www.wren.co for instance, that claims to only invest in offset programs that are i) certified and ii) reduce carbon

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For most people, I would say the best thing you can do is spend your time, energy, and money working to create effective political and policy change at scale. Working to address your personal carbon footprint isn't the best way to do that. So if you were planning to spend $100 on offset credits, consider giving that money to a political cause you believe in instead.

Something that's really important to know about all the new websites and apps that offer carbon offsets are basically just tech wrappers on the existing offsets industry. They sell the same credits from the same projects, credited by the same purportedly third-party standards-setting bodies that are screwing up the system today. If you trust the industry, or the specific individuals vetting your options at one of these new companies, then great; or if you're the sort of person who wants to read through all the project documentation and spend dozens of hours like a committed hobbyist, that's perfectly fine, too.

For most people who are focused on eliminating their carbon footprints, however, I couldn't recommend much that's out there. Here's a good review from Ars Technica on some of the technical issues you'd need to screen for in making your decision.


Many new tech companies aren't doing this. Instead, most are invoking "machine learning" or "satellites" or "blockchain" to pretend away the problems of quality using the buzzwords of Silicon Valley. A few are trying to do better, but it's hard to stand out when your competitors are faking it.

The problem facing you and everyone else is how to tell the difference.

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Thank you. You articulated with arguments the fuzzy reason why I have never bought offsets and instead cut checks to organizations like UCS or EDF!

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So happy to help! Let me add only that some environmental organizations actively promote the use of carbon offsets, so if that's a theory of change you don't believe in then it's something to consider when donating money. Totally your business, just flagging the connection. (Many groups that push offsets also do really important work to advance climate policy in other areas, so it's not a black-and-white situation — but of course your mileage may vary.)

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I would love to read more well-researched articles about climate change theory of change, with specific political/environmental groups called out. Even a "lay of the land" article identifying the pros and cons of each group, which theory of change they subscribe to, etc.

I liked that 2019 "the best climate change charities to donate to" Vox article (https://www.vox.com/future-perfect/2019/12/2/20976180/climate-change-best-charities-effective-philanthropy), but I want a million articles like that, arguing and debating each other, and including political organizations rather than just climate-focused non profits. There must be a debate happening out there, but maybe happening behind closed doors?

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This article raises good points but misses many fundamentals of offsetting. First and foremost, carbon overshoot is guaranteed so there's no path to climate stability without some type of offset. Yes, direct air capture may save the day, but that's way off in a theoretical future. Today we have nature-based solutions, driven largely by voluntary markets. Compliance markets, as noted, are small and somewhat flawed, as this article notes. But organizations like Verra and Gold Standard are working hard to ensure permanence (with a risk pool) and quality for credits around the world, with the voluntary market growing dramatically. In fact, the bar they set is so high that demand significantly outstrips supply right now. Whether its avoided deforestation in peatlands of Indonesia or improved forest management in forests of Pennsylvania, there is a growing body of evidence that offsets can be done well. Most importantly, we have to figure out how to get them right, because there is no other way to sequester emissions at scale today and for the foreseeable future. Unfortunately, this article misses the forest for the trees.

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There's a lot of confusion in this statement, but if you truly think private markets are doing a good job today let me introduce you to Blomberg Green reporter Ben Elgin:



I could go on about "buffer pools" and other protocol design details that are written by financially conflicted parties without a scientific basis for risk management — okay I will!


Anyway, those of us who are old enough to have lived through the financial crisis and the games that financial ratings agencies played in that process — getting paid to rate junk securities as AAA investments — should recognize a shell game when we see one.

By all means, buy these products if you like them.

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I read the Bloomberg piece, which I consider similarly one sided. Cherry picking examples to make a point, rather than offering a comprehensive view of the field. In my mind, the question we need to focus on is how to make offsets real, durable and high quality. There is a ton of work to do on that front. But to dismiss these markets, when the are growing exponentially, seems shortsighted to me. Admittedly I have not read your book yet, so I assume I'm missing a fair bit of the nuance of your arguments. My question to you: If not offsets, what? Or do you disagree that overshoot is guaranteed?

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I think you are mixing up some important concepts. If humanity emits too many GHGs and/or can't get to gross zero emissions, we'll need permanent carbon removal to remove CO2 from the atmosphere and permanently store it somewhere safe. That's a tall order. Almost none of today's offsets do that.


Most offsets credits today avoid emissions and sell credits that enable companies to keep emitting. At best, that leads to a wash — no net GHG reductions, just a shift in where emission reductions occur. But if offsets are anything less than perfect, they lead to an increase in net GHG emissions. Last time I checked, that is a Bad Thing!

Meanwhile, those offsets that pursue carbon removal store tend to store carbon in forests or soils, where it can be expected to last years to decades. In contrast, the carbon cycle effects of fossil CO2 emissions tend to last for centuries to millennia. So if your goal is to permanently address cumulative emissions overshoot or ongoing emissions that can't be abated, and you want to have confidence in the integrity of your investments, then you shouldn't look to today's market to solve this problem.


I spend a lot of my time these days working on strategies to improve a path to permanent carbon removal, and none of those strategies involve pretending that the current offsets market works or that the current arbiters of quality have any business playing that role going forward. I'm mildly optimistic that the very best buyers might demand better outcomes, if pressed, but that'll only happen if people wake up to the complete lack of quality in current markets and the role that private, unregulated standard-setting bodies and their allied NGO rent-seekers have played in the race to the bottom. There is a pattern here, and it's hard not to see it.

It sounds like you think today's market is fine. If that's the case, why do you believe that? What's the path forward that gets us somewhere better?

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I agree with Brad - this Bloomberg piece seemed more like a hit piece on TNC than a nuanced discussion of the problem with nature-based offsets. I completely agree the additionality argument presented for some of these projects, and not every 'conservation' project is a carbon project. Though some are, and offsets are a tried and true way to ensure some sort of financial return for protecting natural ecosystems, rather than relying on philanthropic efforts (which needless to say have woefully under-delivered protection thus far). Completely writing off a growing market for nature-based solutions, many of these that bring with them a host of co-benefits including but not limited to habitat protection, climate resiliency (flood risk reduction, water quality etc..), and job creation, seems incredibly short sighted. The point of avoiding emissions (by protecting these enormous stores of carbon from conversion) is also often overlooked. As many quality nature-based offset projects include actions to increase the resiliency of an ecosystem to withstand fire or other large disturbances, and protect these stores from conversion (which would ultimately release of this stored carbon) - this is an enormous benefit to the fight against climate change that is completely disregarded. There exists a nexus of offsets from permanent removals (ie. CCS) and nature-based removals that bring along this suite of co-benefits - ideally the vast majority of the former and a smaller slice of the latter - though strictly focusing on the poor examples and not amplifying successes seems counter-productive and incredibly discouraging. Granted, overall these should be a short-term solution for the emissions that are difficult to abate, but an important piece in this puzzle none-the-less.

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