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Let’s REALLY Do The Math Part 2: What is the US Carbon Budget and Why?

by Paulina

The Obama Administration has established “17% below 2005 levels by 2020” as the standard by which US carbon mitigation efforts are to be evaluated. Representatives Waxman and Markey and Senator Whitehouse wrote a letter to Barack Obama a couple of weeks ago, urging the president to:

Lay out specific steps federal agencies will take to ensure that the U.S. emissions of heat-trapping gases are reduced by at least 17% below 2005 levels by 2020, the goal you set for the nation during the 2009 United Nations Climate Conference.

Frankly, it’s a fairly random, not to mention unambitious, standard. Historical accounts of where this — and the Obama 2008 campaign’s similar target —  “came from” are available, but I’ve yet to see a logical explanation, a justification, an account of the reasoning behind this target. (If you have the reasoning, please share in the comments.)

It is commonly understood that rich countries need to reduce their emissions by 25-40% below 1990 levels, in order for the risk of exceeding a 2° C (3.6° F) increase, above pre-industrial global average temperature levels, to be about 50%, given a certain set of assumptions and equity considerations.

The US 2005-based standard instead corresponds to 4% (four, not forty percent) below 1990 levels, by 2020.

Climate Central summarized the baseline discrepancy issue as follows, during the UN climate meeting in Copenhagen in 2009:

While it may seem like techno-speak, the question of baseline year is important, because the Kyoto Protocol used the 1990 baseline, when U.S. emissions were 6.148 Gigatons of carbon dioxide equivalent – much lower than the 7.130 Gigatons emitted in 2005 (data from the EPA). Most countries that have ratified and implemented Kyoto want to keep that 1990 baseline, rather than shift it to a later period. The United States signed but never ratified Kyoto, and it is adamantly opposed to the 1990 baseline.

The disagreement about baseline year stems from the fact that nations that implemented Kyoto have generally been working already to reduce emissions. A 1990 baseline would recognize those efforts: they would count toward achieving the ultimate goal. At the same time, a 2005 baseline would benefit any nations that did not work as hard to reduce emissions prior to 2005, and which therefore had relatively high emissions then. The idea is that these countries can now take large steps more easily by harvesting the “low-hanging fruit” of emissions reductions that other nations already tackled before 2005. Many countries that participated in the Kyoto Protocol therefore say that using a 2005 baseline would benefit the United States to the detriment of others.

In addition to these emission reduction percentages and baselines, hordes of other numbers are bandied about: emission intensities, reductions per projected capita, reductions from projected future baselines, and more. At times, the multiple vantage points almost seem to be used to confuse the public on purpose and render all the numbers essentially meaningless…. A meaninglessness that’s encapsulated in US Special Envoy for Climate Change Todd Stern’s comment: “I frequently say that our [“US and other developed nations”] numbers are quite comparable by any number of measures” [2:30]. Yup, with so many measures floating around, a fair number of them are bound to be “comparable by any number of measures,” i.e., essentially meaningless.

This is where “doing the math” comes in. Writing in Rolling Stone last summer, Bill McKibben popularized the vantage point of the cumulative carbon budget and launched the Do the Math campaign (the “cumulative carbon budget” link leads to the  Meinshausen et al. paper which is well worth reading. Brad Johnson’s The $22 trillion carbon bubble is also very helpful.)

The cumulative carbon budget vantage point doesn’t evaluate our carbon mitigation efforts by how much we reduce our emissions relative to projections or relative to how much we used to emit in 2005 or 1990 or some other date. Instead, our mitigation efforts are simply accountable to a cumulative carbon budget.

A political goal of limiting the risk of exceeding a certain temperature increase — to say 20% — implies a certain global 2010-2050 carbon budget, a budget that can be divided among nations based on equity and geopolitical considerations. Of course there will still be disagreements and controversy, but this framework is stunningly simpler and a lot more transparent than emission reduction commitments.

Individual states, whether nation states or US states — along with the rest of us — need to start thinking in terms of the cumulative carbon budgets from which the Do the Math campaign derives, rather than in terms of frames built around counting emissions reductions from some quasi-business-as-usual “baseline.”

Do the Math shouldn’t just be a campaign slogan. The only serious path forward is to finally try to connect the dots between cumulative carbon budgets and US policy. What is the US carbon budget and why?

In Part 3: California + Math = Size Matters, we’ll have a look at a particularly egregious example of how we fall through the looking glass, when we start “counting” from business-as-usual. Also, stay tuned for a Bonus part after Part 3, where we take a look at, and do the math of, the new climate legislation proposed by Senators Sanders and Boxer.

Let’s REALLY Do The Math: Part 1  Part 3

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