The Warming Limit Approach

Via Climate Progress, we learn about a warming limit-based approach to address the climate problem.

LOL Cats
The authors acknowledge that “defining a warming limit implies a greenhouse gas budget.” Nonetheless, it does seem somewhat silly for world leaders to jet to Copenhagen, sit around the table, argue about the heat, then jet off again after agreeing and shrugging, “What can you do about the weather?”

The warming-limit approach is analogous to how businesses conduct planning under uncertainty: Set a long-term goal, then work backward to determine how to achieve it, modifying plans dynamically as developments dictate. It’s operationally much more useful than a target for a single year. In fact, it can be used to derive such targets over many years, once the budget is allocated to developed and developing countries. It also has advantages over conventional, forward-looking policy analyses, which are hamstrung by the inherent limitations of economic forecasting models in accurately predicting the future.[vi]

Using a warming limit in this way prompts us to ask questions like “What are the least expensive options for meeting the target?” or “How many emission-free power plants must be built per week to meet the target, and how much capital would that require?” or “How fast must energy efficiency improve to meet the target given projected economic growth?” The answers to such questions help us identify the options that are most cost-effective, feasible, and desirable, and allow us to envision the kind of world we want to create.

The 2-degree warming limit is demanding—it implies halting growth in absolute global greenhouse gas emissions within the next decade, with reductions of at least 50% by 2050 compared to 1990 levels, and larger reductions soon afterward.[vii] It also has other implications that most policy makers do not yet fully appreciate:

(1) We shouldn’t wait: Delaying action only eats up the emissions budget, locks in emissions-intensive infrastructure, and makes the required reductions much more costly and difficult later. Early action also brings the costs of technologies down through economies of scale and learning-by-doing, a fact usually ignored by ill-informed climate skeptics.

(2) We need to move quickly on many fronts: The rate of change in energy systems needed to stay within the budget[viii] will require broad societal mobilization, rapid innovation, and major investments in science, technology, and education not unlike those undertaken by the United States after the USSR launched Sputnik in 1957.[ix] One key to rapid change will be the development of new technologies that consumers prefer even if they initially carry a higher price—much like early fossil fuels, such as kerosene, were preferred to whale oil for lighting in the mid-1800s;[x]

(3) We can’t burn it all: More than half[xi] of the Earth’s remaining economically recoverable fossil fuel reserves must be kept in the ground to achieve climate stabilization (or, if burned, their carbon emissions will need to be stored securely). A price on carbon and significant reductions in the costs of low carbon technologies are the two most important means for achieving this difficult goal.

The 2-degree warming limit provides guideposts for a real solution to the climate problem, yielding insights available from no other approach. We’ll need to apply these insights, invest in a large portfolio of promising options, fail fast, and learn as rapidly as we can. There’s simply no more time to waste.


[i] Jonathan Koomey is a Visiting Professor at the Yale University’s School of Forestry and Environmental Studies, and Florentin Krause is a researcher living in Richmond, California. Krause was the principal investigator and Koomey was one of two other coauthors of the first systematic attempt to evaluate the implications of a warming limit-based approach to addressing the climate problem (Florentin Krause, Wilfred Bach, and Jonathan G. Koomey. 1989. From Warming Fate to Warming Limit: Benchmarks to a Global Climate Convention. El Cerrito, CA: International Project for Sustainable Energy Paths. <http://files.me.com/jgkoomey/9jzwgj>). It was republished in 1992 as Florentin Krause, Wilfred Bach, and Jonathan G. Koomey. 1992. Energy Policy in the Greenhouse. NY, NY: John Wiley and Sons.

[ii] Baker, Peter. 2009. “Poorer Nations Reject a Target on Emission Cut.” The New York Times. New York, NY. July 9. <http://www.nytimes.com> and ENS. 2009. “G8 Leaders Aim to Hold Global Warming Below Two Degrees Celsius.” Environmental News Service. Seattle, WA. July 8. <http://www.ens-newswire.com/ens/jul2009/2009-07-08-01.asp>

[iii] For discussion of historical temperatures and the 2-degree limit see Chapter 1 in Krause et al. 1992 in footnote i above.

For more recent assessments of predicted impacts see the Working Group I and Working Group II reports from the IPCC’s Fourth Assessment Report.

[iv] See the interview with White House Science Advisor John Holdren here and here.

[v] See the Intergovernmental Panel on Climate Change Fourth Assessment Report, The Physical Science Basis.

[vi] See Craig, Paul, Ashok Gadgil, and Jonathan Koomey. 2002. “What Can History Teach Us?: A Retrospective Analysis of Long-term Energy Forecasts for the U.S.” In Annual Review of Energy and the Environment 2002. Edited by R. H. Socolow, D. Anderson and J. Harte. Palo Alto, CA: Annual Reviews, Inc. (also LBNL-50498). pp. 83-118, Koomey, Jonathan G., Paul Craig, Ashok Gadgil, and David Lorenzetti. 2003. “Improving long-range energy modeling: A plea for historical retrospectives.” The Energy Journal (also LBNL-52448). vol. 24, no. 4. October. pp. 75-92, and DeCanio, Stephen J. 2003. Economic Models of Climate Change: A Critique. Basingstoke, UK: Palgrave-Macmillan. Economic models are far less reliable than the climate models because the underlying structural attributes of economic systems are not constant in the same way that physical systems are constant.

[vii] Meinshausen, Malte, Nicolai Meinshausen, William Hare, Sarah C. B. Raper, Katja Frieler, Reto Knutti, David Frame, and Myles R. Allen. 2009. “Greenhouse-gas emission targets for limiting global warming to 2 degrees C.” Nature. vol. 458, April 30. pp. 1158-1162.

[viii] See Chapter 6 of Krause et al. 1992 (in footnote i) for analysis of logistic feasibility.

[ix] The first use of the Sputnik analogy of which we’re aware was Koomey’s testimony before the Joint Economic Committee of the U.S. Congress in July 2008 (Testimony of Jonathan Koomey, Ph.D. for a hearing on “Efficiency: The Hidden Secret to Solving Our Energy Crisis“. Joint Economic Committee of the U.S. Congress. U.S. Congress. Washington, DC: U.S. Congress. July 30, 2008.). Tom Friedman of the New York Times started using this analogy independently in September 2009.

[x] Lovins, Amory B., E. Kyle Datta, Odd-Even Bustnes, Jonathan G. Koomey, and Nathan J. Glasgow. 2004. Winning the Oil Endgame: Innovation for Profits, Jobs, and Security. Old Snowmass, Colorado: Rocky Mountain Institute. September. <http://www.oilendgame.com&gt.

[xi] See Chapter 4 of Krause et al. 1992 (in footnote i) and Meinshausen et al. 2009 (in footnote vi).


I guess, if there actually is some action rather than more jet setting words, then the warming limit approach might have some usefulness. The following graph illustrates the limitation to such an approach.

Temperature and CO2 plots from the Vostok ice cores
The most compelling feature of a paper about the plight of the world’s coral reefs was the same data, plotted a different way: temperature vs. CO2, rather than temperature and CO2 over time.

Temperature versus GHG charting clearly indicates the critical need for a change in course, which must be accomplished by a reduction in emissions from the combustion of fossil fuels. The graph shows the critical 2 degree C thermal limit.

At present we are experiencing what climate modelers call the transient response to CO2 forcing. If CO2 concentrations froze now, global temperatures would continue to rise until the climate reached equilibrium. Thus, in some sense, reacting to an increase in temperature is like reacting to an increase in sea level. The reaction is well after the forcing has occurred.

Unfortunately, the above graph used an older CO2 limit. There is a general consensus among climate scientists that 350 ppm is an appropriate CO2 threshold. Will someone please shut off those klaxons.

While the authors dodge the coal zombies recalcitrance to reduce GHGs, they do summarize well the complex issues of feasibility and equity that COP15 is supposed to address.

Many argue that developing countries like China can legitimately claim much of the emissions budget because they have large populations and have consumed relatively small amounts of fossil fuels thus far. But developed countries like the United States can’t phase out greenhouse gases overnight. In addition, many emissions from emerging economies are attributable to the manufacture of exported goods.

Of course, talk about budget is a comfortable place for our world leaders. They can trance out as numbers flash on the screen. It is a comfortable place because, as we all know, figures don’t lie.

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2 Comments

  1. jcwinnie
    Posted 2009-12-7 at 11:24 am | Permalink

    Armond Cohen, Co-Founder and Executive Director of the Clean Air Task Force and HuffPo contributor also defines the challenge facing Copenhagen. “Coal alone provides 40 percent of the world’s electricity (50 percent in the United States; 80 percent in China),” posts Cohen, “and accounts for about 35 percent of the world’s energy-related carbon dioxide.”

    What’s more, China, India and other developing countries plan to double or triple their coal power in the coming decades, because it’s cheap and abundant, and other sources are limited. And the United States won’t abandon its coal plants, which provide half of the nation’s power.

  2. jcwinnie
    Posted 2009-12-9 at 11:18 am | Permalink

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