Econ 350: Can we still afford to save the climate?

This is a guest post from economist Eban Goodstein, Director of the Bard Center for Environmental Policy.  It is partially excerpted from this Grist piece.  He and his colleagues at the E3 Network have just released a detailed study on The Economics of 350.  The figure compares cumulative emissions for a 350 ppm CO2 trajectory.

cumulative emissions graph

Recently, many climate scientists have doubled down on the “safe” level for atmospheric CO2.  To avoid global warming catastrophe-collapse of the continental ice-sheets and sea level rise of dozens of feet — prominent voices led by NASA’s James Hansen are now telling us we have to get down to 350 ppm, and quickly.

Game over?

No. Instead, time to adjust our thinking about what is possible.

Several co-authors and I recently completed a report for Economics for Equity and the Environment Network (E3), surveying the economic studies informed by recent science. The report  found that quicker action aimed at 350 makes good economic sense. With likely investments of about 1-3% of global GDP, we could rewire the planet with clean energy, rebuild global forests to trap billions of tons of carbon, create jobs, and stabilize the climate. And depending on the price of oil, these investments might actually save us money.

Is 350 Possible?

Hansen et al. (here, see Figure 1) described a detailed scenario for reducing greenhouse gas emissions with the goal of reaching 350 ppm CO2 by 2100. It included phasing out coal completely (or achieving 100% carbon capture) by 2030, along with a combination of large-scale reforestation, avoided deforestation and carbon capture and storage to withdraw huge quantities of CO2 from the atmosphere. To reach the 350 target by 2100, the world would have to quickly go beyond reductions to achieve net negative emissions-removing more greenhouse gases from the atmosphere than are emitted each year.

Our report contrasts Hansen’s scenario with a less demanding but still quite ambitious trajectory which does not require the world to achieve negative net emissions. In this scenario, the world reaches 350 ppm CO2 by 2200. Emissions are reduced to 54 percent of 1990 emissions by 2020 and 3 percent by 2050, and then zero out, but do not go negative.

The bottom-line on the technical side: Decarbonizing by 2050 is possible with, roughly, the suite of technologies now available or on the near-term horizon. Very aggressive policy, however, will still be required very soon to drive down the costs of renewables, to redesign cities, reimagine transport and agricultural systems, and insure that all efficiencies are captured. Doing all this gets the world to 350 by 2200. Taking the additional steps to achieve negative emissions (and 350 by 2100) would require the development of large-scale, cost-effective sequestration technologies that go well beyond reforestation.

Economics, 350 and Politics

At least four research groups have modeled global scenarios that lead to 350 ppm CO2. One finds that in a world with unemployed labor and other resources, the stimulus from new climate investments might accelerate economic growth. The other three groups find net annual costs that are generally between 1 percent and 3 percent of world output. These studies are consistent with the Stern Review, the reports by McKinsey, and others, suggesting that achieving 450 ppm would cost around 1% or less of global GDP.

Both of these targets, 350 or 450, become a lot cheaper if oil prices return soon to $150 a barrel. If peak oil drives prices that high in the coming decade, then decarbonizing at a pace to hit 350 could lead to economic gains.

Dropping the global climate target from 450 ppm to 350 ppm of atmospheric CO2 may appear to present an impossible task. In fact, it leaves us with qualitatively the same challenge. Achieving 350 simply requires accelerating a global technology revolution that will yield many benefits- in terms of climate stability, energy security, and economic payback. And estimates of the scale of the investment needed to complete that revolution-and complete it on time-are affordable.

In Europe, the US and China, the politics of 450 ppm are beginning, just beginning, to come into view. Our new study sets the stage for a longer-term discussion.  The obstacles to achieving 350 are not technical nor are they economic.

JR:  For the science behind 350 ppm, see “Stabilize at 350 ppm or risk ice-free planet, warn NASA, Yale, Sheffield, Versailles, Boston et al.” Since the science is preliminary and it is not not yet politically possible to get to 450 ppm, let alone 350, my basic view, as expressed in that post, is Let’s start working now toward stabilizing below 450 ppm, while climate scientists figure out if in fact we need to ultimately get below 350.  Either way, this is what needs to be done technology-wise:  “How the world can (and will) stabilize at 350 to 450 ppm: The full global warming solution.”  The difference between the two targets is that for 450 ppm, you need to do the 12-14 wedges in four decades.  For 350 ppm, you (roughly) need 8 wedges in about two decades plus another 10 wedges over the next three decades (and then have the world go carbon negative as soon as possible after that), which requires a global WWII-style and WWII-scale strategy as discussed here.  I would like to get back to 350 ppm by 2100, but I tend to think that 2150 is “more likely.”  Either way, the cost of doing so is certainly far cheaper than the cost of failing to do so (see “Intro to climate economics: Why even strong climate action has such a low total cost — one tenth of a penny on the dollar“).

Comparing cumulative emissions for a 350 ppm CO2 trajectory

15 Responses to Econ 350: Can we still afford to save the climate?

  1. Just to say thanks to Eban et al for this fine paper, and to Joe for featuring it. And to let y’all know that two weeks from now on Our International Day of Climate Action, it looks like there will be well more than 2000 actions in almost every country on earth. (Country 144 came on line today–Iran, with 4 actions and a Farsi website). Check out

  2. Leland Palmer says:

    The target of 350 ppm is a lot easier to meet if we convert the coal fired power plants to enhanced efficiency bio-energy plus CCS “carbon negative” power plants.

    Think of the atmosphere as a tub, and our CO2 emissions as water filling that tub.

    Most of the carbon neutral energy options we are pursuing are equivalent to just filling that tub with water more slowly.

    Carbon negative energy options, including bio-energy with carbon capture and storage would be equivalent to actually pulling the plug, and starting to drain the tub.

    Reforestation is somewhat equivalent to carbon negative energy in that it actually takes carbon out of the atmosphere, but stores carbon in trees, which are vulnerable to increasingly common wildfires.

    It’s a lot easier to get to 350 ppm with carbon capture and storage (CCS), especially Bio-energy plus CCS.

  3. Adam Sacks says:

    First of all, Hansen didn’t say that 350 ppm was a target – he said 350 ppm was a best estimate of a *maximum* safe level, and that the safe level was likely lower.

    Next, to imagine that we have until 2100 to get to what is likely a woefully inadequate 350 ppm is purely delusional. Tipping points (positive or amplifying feedback loops) have tipped. That’s why we are breathlessly watching phenomena today that were “scheduled” for decades or a century hence – i.e., part of the amplification of feedback loops is acceleration. There is absolutely no reason at this point to assume that the acceleration and the *rate* of acceleration will not continue.

    With respect to a 2°C “safe upper limit,” were we willing to confront climate reality we would easily see this limit is sheer nonsense on the face of it. We haven’t even hit 1°C yet, and we’re already obviously beyond anything resembling a “safe limit” – ice melting, massive droughts, mistimed rains, disrupted insect reproductive cycles and devastated forests – just how much convincing do we need? We don’t have decades to turn this around, and positive feedbacks engage before we are able to see them, so who knows what else has tipped.

    I do agree that we need to pull carbon out of the atmosphere as quickly as possible while reducing our emissions to zero. Although increasing afforestation and eliminating deforestation deserve immediate attention, a far quicker natural method appears to be holistic management of grasslands (see and deep and long-term soil sequestration of carbon that doesn’t cycle back into the atmosphere in a few decades (it also costs relatively little and can actually generate income).

    Isn’t it time to abandon all the high-tech harebrained profit-making schemes, like the ones that brought us global warming in the first place? Do we imagine for a moment that we’ve suddenly become smart enough to avoid unpleasant unintended consequences such as climate destruction and get a free pass to engage in our technophiliac perversities?

    Current economic arguments are entirely inconsequential before the forces of nature. We have to adjust our means of exchange in accordance with the laws of ecology – nature will not accommodate our misplaced fondness for currency, GDP, and other artificial constructs.

    If we had any understanding of such basic ecological concepts as overshoot, carrying capacity, nutrient cycles, etc. we would make drastic changes in conduct immediately (if, that is, we want to continue living in anything resembling civilization, or even living at all). In any case, we will not continue with our profligate ways, no amount of “rational” argument and economic “analysis” will make an iota of difference in the processes of the physical universe.

    History has told us repeatedly: We either mend our lethally errant ways, or nature will mend them for us.

  4. Jeremiah says:

    In response to Leland, there are just so many unknowns in the case of CCS. It seems like another case of people finding a solution for problem that is vastly more convoluted, unpredictable, and dangerous than the problem itself.

    In defense of CCS, I think we have to look at the realities on the ground. Transitioning to a clean energy planet will be good for the world economy. The only problem is that it represents a realignment of beneficiaries. Big fossil fuel will lose out to yet-unknown industries. Unlike coal and oil however, these yet-unknowns don’t have huge and powerful lobbying firms representing their interests in congress. CCS might simply be the only way of getting powerful climate legislation through politically.

  5. Remi says:

    A whole societal shift to fix a symptom of a societal problem without fixing or even mentioning the problem (socioeconomic system that treats nature as an externality). How will our current agricultural system work without a high carbon footprint or even more importantly collapsing water supplies? What about the projected collapse of the fisheries and on and on and on?
    What happens if reaching 350ppm by 2200 brings us to a point where permafrost and methane hydrate emissions surpass current GHG emissions? No one knows when that will happen, except that all signs point to the fact that it will likely occur before we expect it to happen. It is a race to reach a “safe” atmospheric GHG concentration, whatever that level may be. Before then, we are literally holding a match under the methane bomb stored in the North and hoping it doesn’t blow up.

  6. “One [study] finds that in a world with unemployed labor and other resources, the stimulus from new climate investments might accelerate economic growth.”

    I appreciate this paper and I am all for the 350 target, but this quote reminds me of the reason that economists are beginning to say that GDP is not a measure of well-being, so economic growth is not necessarily good thing.

    GDP measures all economic activity. Thus, if someone gets drunk to drown his sorrows, then gets into a car crash on the way home so he needs a new car and long hospital stay, all of this increases GDP. Redefining Progress has written at great length about this; and Nobel-Prize-Winning economist Joseph Stiglitz talks about it in his recent report for the government of France.

    In the coming century, more and more of the world’s GDP will be made up of what economists call “defensive expenditures” – expenditures that are needed to deal with the costs of growth. And those defensive expenditures should be counted as costs, not as benefits.

    If we need immense investments in energy to avoid global disaster, that is also a cost rather than a benefit. We shouldn’t be touting these investments on the grounds that they will increase the rate of economic growth. Instead, the need for these investments should make us question the value of endless economic growth.

    As Herman Daly has said:
    “Once we have gone beyond the optimum, and marginal costs exceed marginal benefits, growth will make us worse off. Will we then cease growing? On the contrary, our experience of diminished well-being will be blamed on the traditional heavy hand of product scarcity, and the only way the orthodox paradigm knows to deal with increased scarcity is to advocate increased growth – this will make us even less well off and will lead to the advocacy of still more growth! Sometimes I suspect that we are already on this ‘other side of the looking glass,’ where images are inverted and the faster we run, the ‘behinder’ we get.”

  7. Wes Rolley says:

    Having this discussion based on the absolute numbers of 350 or 450 ppm is a blessing. I know from many conversations that discussions focused on cutting emissions based on 1990 levels, or 2005 levels, etc. only adds to the confusion and makes good people wonder what is being hidden.

    We should demand that all work on climate change legislation express their goals in terms of the impact on ghg levels and not in the relativistic terminology now used.

    Maybe this post is a good start.

    Wes Rolley
    CoChair, EcoAction Committee, Green Party US

  8. Kevin Whilden says:

    I like the framework of this analysis, however I am concerned that it does not properly treat the potential risks of a ‘slow’ route to 350 ppm by 2200. Given the amplifying feedbacks of CO2 emissions that exist from permafrost, diminshed ocean circulation, and continental-scale forest fires, there is no such thing as a slow route to 350 ppm. I think even the ‘faster’ route of Hansen et al. of 350ppm by 2100 would not be fast enough to prevent runaway amplifying feedbacks.

    As Canadell et al recently published, the frozen carbon in the permafrost is much higher than prior estimates. They say, “The potential for significant feedbacks from permafrost carbon could be realised with only a small fraction of currently frozen carbon released to the atmosphere. For example if only 10 per cent of the permafrost melts, the resultant feedback could result in an additional 80 ppm carbon dioxide equivalent released into the atmosphere, equating to about 0.7°C of global warming.”

    So how are we going to get to 350 ppm when the Arctic emits another 80ppm while we’re waiting for Mother Nature to soak up the rest? And unfortunately, it’s not just the Arctic… the Amazon rainforest is expected to become a net source of CO2 by 2050 due to massive wildfires. Even worse, each amplifying CO2 emission increases emissions from elsewhere. The total CO2 emission potential from the Arctic is over 200 times the historical total of human CO2 emissions!

    I think if this report had incorporated the amplifying CO2 feedbacks, it would have called for more direct action to reduce CO2 sooner rather than later.

  9. David B. Benson says:

    Sorry, but 350 ppm is too high as a permanent goal. For example, coral bleaching was first noticed when CO2 concentrations were but 320 ppm. Also around then several glaciers began to melt back.

    Jeremiah — Some sequestrations methods certainly appear to be risk free, but possibly rather costly:

  10. Mike#22 says:

    Actually, Hansen et al outlines a fast approach to 350 ppm: “The final wedge in Figure 6 is designed to provide an indication of the degree of actions that would be required to bring atmospheric CO2 back to the level of 350 ppm by a time close to the middle of this century, rather than the end of the century.” (page 31 of 35 ) Figure 6 (page 12 of 35) actually shows CO2 going below 300 ppm in about 100 years.

    I guess that I am in the minority here, but I believe the technical and economic details of getting to negative emissions are easy–ready to go now. Hopefully politicians will see this too, and soon.

  11. Roger says:

    Well, while everyone is engrossed in contemplating how quickly the damn ship is going to sink, at least Bill Mckibben and his crew are working hard to wake up the captain and the other passengers!

    You see, on this ship, we need a majority of passengers to agree on whether we should turn on the bilge pumps. It’s almost midnight, everyone’s had a lot to eat and drink, and nearly everyone’s asleep.

    Some of the other wakeful folks are suggesting that everyone keep quiet. Others are seen to actually be drilling holes in the hull!
    I’m with Bill. Let’s make some noise on October 24th. It’s time!

  12. Steve Bloom says:

    Leading coral reef experts have weighed in with a new review paper (title/abstract):

    The coral reef crisis: The critical importance of [staying below] 350 ppm CO2

    “Temperature-induced mass coral bleaching causing mortality on a wide geographic scale started when atmospheric CO2 levels exceeded 320 ppm. When CO2 levels reached 340 ppm, sporadic but highly destructive mass bleaching occurred in most reefs world-wide, often associated with El Niño events. Recovery was dependent on the vulnerability of individual reef areas and on the reef’s previous history and resilience. At today’s level of 387 ppm, allowing a lag-time of 10 years for sea temperatures to respond, most reefs world-wide are committed to an irreversible decline. Mass bleaching will in future become annual, departing from the 4 to 7 years return-time of El Niño events. Bleaching will be exacerbated by the effects of degraded water-quality and increased severe weather events. In addition, the progressive onset of ocean acidification will cause reduction of coral growth and retardation of the growth of high magnesium calcite-secreting coralline algae. If CO2 levels are allowed to reach 450 ppm (due to occur by 2030–2040 at the current rates), reefs will be in rapid and terminal decline world-wide from multiple synergies arising from mass bleaching, ocean acidification, and other environmental impacts. Damage to shallow reef communities will become extensive with consequent reduction of biodiversity followed by extinctions. Reefs will cease to be large-scale nursery grounds for fish and will cease to have most of their current value to humanity. There will be knock-on effects to ecosystems associated with reefs, and to other pelagic and benthic ecosystems. Should CO2 levels reach 600 ppm reefs will be eroding geological structures with populations of surviving biota restricted to refuges. Domino effects will follow, affecting many other marine ecosystems. This is likely to have been the path of great mass extinctions of the past, adding to the case that anthropogenic CO2 emissions could trigger the Earth’s sixth mass extinction.

    Hell and high water indeed. For additional context, see this discussion of the “marine nutcracker.”

    And if that wasn’t enough, new results announced last week (but not published yet) find a sharp acidification trend in the Arctic ocean, one that’s going to get a lot worse very soon (excerpt from UK Telegraph article via the excellent Ocean Acidification blog):

    Arctic Ocean acid ‘will dissolve shells of sea creatures within 10 years’

    “The Arctic Ocean is becoming acidic so quickly that it will reach corrosive levels within 10 years, a leading scientist has warned.

    “Waters around the North Pole are absorbing carbon dioxide at such a rate that they will soon start dissolving the shells of living sea creatures.

    “The potentially disastrous consequences for the food chain have been highlighted by Professor Jean-Pierre Gattuso of the National Centre for Scientific Research in France.

    “His team of oceanographers have produced startling predictions about the acidity of the Arctic Ocean after research carried out on the Svalbard archipelago, a group of islands half way between Norway and the North Pole, revealed that the problem is more advanced than scientists thought.

    Their forecasts suggest that by 2018, 10 per cent of the ocean will be corrosively acidic, rising to 50 per cent in 2050. By 2100 the entire Arctic Ocean will be inhospitable to shellfish, they predict.

    “‘This is extremely worrying,’ Prof Gattuso told the Oceans of Tomorrow conference in Barcelona.

    “‘We knew that the seas were getting more acidic and this would disrupt the ability of shellfish – like mussels – to grow their shells. But now we realise the situation is much worse.’


    450 ppm is looking harder and harder to defend.

  13. Steve Bloom says:

    I have a multi-link comment in moderation, Joe. TIA.

  14. Aaron Lewis says:

    Economic reports are not produced instantly, so very likely this report is based on data circa 2007 such the IPCC Report. In that report, sea level rise was forecast to be on the close order of 0.4 meters by 2100. More recent work by many of the same authors place sea level rise by 2100 on the close order of 2 meters – a 5 times increase in two years without any kind of a clear statement that we now fully understand all the ice dynamic issues and this is as bad as it can get. In short, sea level rise clearly can be more than 2 meters in the next century.

    Two meters of sea level rise would impair the infrastructure around Washington DC and other capitals damaging our command and control systems. It would impair the infrastructure that support our capital markets that is necessary for large projects. And, it would damage much industrial infrastructure including that needed for food production. All of which could occur in the next hundred years. If the target is to have CO2 at 350 ppmv by 2100, all three functions are likely to end up in water up to their eyebrows.

    It is very hard to get anything done under flood conditions. Productivity goes down and cost go up. The costs of global warming are likely to be vastly greater than anything suggested by any economist looking at the IPCC 2007 Report. The costs of global warming are so much greater that it justifies more aggressive goals and extreme efforts to meet such goals.

  15. tony lovell says:

    Please take a few minutes and look into the one CCS option that has worked for millions of years – Bio-CCS – the natural miracle of photosynthesis in action.

    In particular, could I ask each of you to look a little more into the massive and positive impact changed grazing management could have. Professor Tim Flannery has stated that sequestering carbon into the soils of our grazing lands is one of the best means we have available to us for dealing with climate change.

    There is growing concern for significant action to avoid catastrophic climate change. Please take a few minutes and look through the presentation on Soil Carbon at

    Not enough people are yet aware of Soil Carbon and the critical role it can play in helping to reverse the impacts of global warming.

    Did you know that just a 1% change in soil organic matter across just one-quarter of the World’s land area could sequester 300 billion tonnes of physical CO2?

    Recent Australian studies have shown that a 1% change can occur within a few years – and in fact up to 4% changes were measured in some areas. The management changes required to achieve these increases are very readily implemented. I hope you find the presentation of interest.