Ditch the 2°C limit? A costly detour

David Victor and Charles Kennel write in a recent commentary published by Nature “Politically and scientifically, the 2 °C goal is wrong-headed.” Their commentary has prompted a number of responses – see article in The Guardian by Adam Vaughan and rebuttals by Gavin Schmidt, Bill Hare and others, and Joe Romm.

Victor and Kennel argue that the 2 °C limit suffers from two political problems. First, they assert, keeping below 2 °C is unachievable without “heroic assumptions” about immediate global cooperation and widespread availability of technologies that have not been demonstrated at scale. Second, the 2 °C threshold does not translate into a specific and certain quantity of emissions, and therefore “does not tell particular governments and people what to do.”


Scientifically, the basis for the 2 °C limit, according to Victor and Kennel, is tenuous, in part because changes in average global surface temperature does not track in lock step with climate forcing and climate risks on short time scales. They take the position that a single index of climate change risk is not possible given the complexities of how changes in carbon dioxide concentrations alter climate and other earth systems, and the consequent risks to ecological systems and humans. They advocate for development of a set of indicators, or “planetary vital signs,” to be used by policy makers and the UNFCCC to gauge climate stresses and possible impacts that are “better rooted in the scientific understanding of climate drivers and risks.”

Gavin Schmidt, director of NASA’s Goddard Institute for Space Studies, wrote an excellent rejoinder in Realclimate. He also posted a comment to an article in The Guardian about the Victor-Kennel commentary that nicely matches my take: “If you are driving in completely the wrong direction, arguing about where you’ll park if you arrive isn’t your highest priority.” I have significant doubts about the viability of reaching a comprehensive, top-down, legally binding agreement at COP21 in Paris. But urging parties to the UNFCCC to revisit the hard-won agreement to try to limit warming to < 2 °C, and consider replacing it with targets for an array of planetary vital signs, is an invitation to inaction that would have dangerous repercussions.

Do read Gavin Schmidt’s more detailed assessment of why the 2 °C limit should not be ditched. He makes a good case for the scientific validity for using average global temperature as a reasonable indicator of climate risk, and counters the assertion that the 2 °C limit is technically or economically unachievable.

Steve Schneider: “We are not in the business of equal time for all claims”

Stephen Schneider (1945-2010) placed great importance on scientists engaging with the public and policy makers to raise awareness and understanding about climate change, and he was one of the most audible scientific voices on this issue in the public sphere. You’ll find a number of references to Steve in two of the books that we read over the summer for the Mosaic — Weart’s Discovery of Global Warming and Oreskes & Conway’s Merchants of Doubt.

I’m reading Steve’s book Science as a Contact Sport in which he recounts in detail some of the events described by Oreskes and Conway in which Steve was a principal participant or observer. In his book, Steve addresses the “doctrine of balance” as applied by media in news coverage of climate change. He writes that the doctrine

“is pernicious when applied to science, because science is rarely just two-sided like two-party politics, where balance is appropriate. Scientists winnow out the relative likelihoods of all of the various potential outcomes. We are not in the business of equal time for all claims; we are in the business of quality of evidence assessment. Therefore, what we need to do is report the relative strength of the arguments, not give equal time to all claimants of truth.” (pp 119-120).

I had the privilege of working with Steve on the IPCC’s 2001 report. This photo was taken of us at a meeting in Geneva near the end of our work on the Synthesis Report.  Schneider-Leary TAR SYR Geneva copy









You can watch Steve talk about Science and Distortion in this video produced by Stephen Thomson of Plomomedia:

Stephen Schneider: Science and Distortion



US: political agreement, not a legally binding treaty

The New York Times reported yesterday that President Obama is seeking an international agreement that would be based on voluntary pledges that would not be legally binding (Obama seeking climate accord in lieu of treaty, Aug 26, 2014). This is a critical question for the UN climate negotiations that we will attend in Lima in December, and one that we will discuss during the semester. Many Parties to the UN Framework Convention on Climate Change (UNFCCC) take the view that, for international efforts to be effective at preventing ‘dangerous’ climate change, nations must make commitments to reduce emissions of greenhouse gases that are legally binding — similar to the approach embodied in the Kyoto Protocol, but with more stringent commitments that would apply to all major emitters of GHGs, if not all nations. Other Parties have promoted a different approach in which nations make pledges to take action on climate change. The US is an important proponent of this approach, and has been for some time. Under this alternative approach, each Party would, within some agreed parameters, decide the form and stringency of its pledge. This approach is embodied in the Copenhagen Accord and Cancun Agreements of the UNFCCC. Enforcement would not be through international legal channels, but through political pressure brought to bear by other nations, and a desire on a national government to create or maintain a reputation of being true to its word. The Obama administration has referred to this as “name and shame.”

Later this semester we will read a paper by Daniel Bodansky of the University of Arizona that compares these two approaches, and recommends that Parties to the UNFCCC draw on both in seeking a way forward. See his paper The Durban Platform: Issues and Options for a 2015 Agreement, from the Center for Climate and Energy Solutions.

When you read the NY Times article, also read some of the comments. You’ll see that the ‘Merchants of Doubt’ have been effective at seeding confusion and misinformation about climate science.