Durban, two degrees and what that could mean

The latest climate change conference is over, and just as it looked as though it would end in total disarray, something got agreed at the last minute. I’m not sure whether to be surprised, given this is what seems to happen every time! Matthew Lockwood gives some helpful analysis of how we may have got here, and the possible consequences.

What have we got out of the process? A roadmap to a legally-binding treaty to be agreed in 2015 and come into force by 2020. Better than a set of voluntary agreements which would probably have got us nowhere. At least on this point, I’m inclined to go along with Michael Jacobs and be (very) cautiously optimistic. World leaders reaffirmed the need to take action to keep temperature rises under 2 degrees, and the climate deniers failed to get much of a hearing. But that we see the possibility of action nine years off as a good outcome is really a sign of how low our hopes have got. As 350.org’s blog writes, campaigners have managed to avert the worst possible outcome, but there is still plenty of pressure needed over the next few years, in getting the strongest possible treaty agreed by 2015, but also to push for bottom-up solutions and changes to individual behaviour.

But back to these two degrees. What does the science say? There are a couple of very interesting articles at Grist by Dave Roberts, here and here which in turn reference a paper in the Proceedings of the Royal Society by Kevin Anderson and Alice Bows. Roberts’ are worth reading in full, Anderson/Bows is rather more technical and involves analysis of the various future emission pathways.

The key points as I see them:

  • Political rhetoric talks about ”not exceeding” a temperature rise of 2 degrees Celsius, or at most a very low risk. An absolute guarantee is not possible, and in any case, the options for any sort of high likelihood of staying under 2 degrees are rapidly running out. Such rhetoric should only be combined with a call for urgent action, not delaying for a few years.
  • It is believed that delaying action now can be compensated for by increased emissions reductions in the future. Theoretically true on a global scale. If we assume that there is a hard limit on the amount of carbon we can emit over the whole of human civilisation – not unreasonable given the length of time CO2 stays in the atmosphere – then once we hit this limit, that’s it. In fact, if we divide this budget up equitably, then the Global North has already exceeded its share by a fair bit.
  • Of the emissions pathways Anderson and Bows consider, the more optimistic ones are now disconnected from reality in that they assume action has happened and we hit a global peak in emissions about 2010. (2010 saw a record rise in emissions of 5.9% and a further rise in 2011 seems inevitable.) Even the pessimistic ones require a peak by about 2020 to have any chance of staying under 2 degrees. And all of this is aimed at a 450ppm CO2e atmosphere which is now reckoned to be on the high side.
  • The 2 degree target in itself is now out of date. Back in 2001, the scientific consensus put it at the boundary between “acceptable” and “dangerous” climate change. Unfortunately on new research, the likely effects at 2 degrees are now seen as worse, so 2 degrees is more realistically a boundary between “dangerous” and “extremely dangerous” climate change.
  • It is often claimed that climate policies didn’t take economics into account. This isn’t true. The Stern report and others argued for a 3-4% year-on-year reduction emissions as this is what they reckoned was the maximum the economy could stand and still keep growing. (Other sources would give 3-4% as overoptimistic). We’re now at the position where if we want to only reduce by this level we need to peak by 2015. If we delay the peak until 2020, we need 10% reductions thereafter.
  • A peak by 2020 and then only 3-4% reductions thereafter – and this seems to me the absolute maximum that an agreement on the Durban roadmap will get us – will net us something in the order of 4 degrees of temperature rise this century, which is heading into runaway territory. The science according to Anderson: “a 4 degrees C future is incompatible with an organized global community, is likely to be beyond ‘adaptation’, is devastating to the majority of ecosystems, and has a high probability of not being stable.”

Where does this leave us? Anderson and Bows close their paper with the following:

However, this paper is not intended as a message of futility, but rather a bare and perhaps brutal assessment of where our ‘rose-tinted’ and well intentioned (though ultimately ineffective) approach to climate change has brought us. Real hope and opportunity, if it is to arise at all, will do so from a raw and dispassionate assessment of the scale of the challenge faced by the global community. This paper is intended as a small contribution to such a vision and hope.

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