Ditch the 2 °C warming goal
Average global temperature is not a good indicator of planetary health. Track a range of vital signs instead, urge David G. Victor and Charles F. Kennel.
For nearly a decade, international diplomacy has focused on stopping global warming at 2 °C above pre-industrial levels. This goal — bold and easy to grasp — has been accepted uncritically and has proved influential.
The emissions-mitigation report of the Fifth Assessment of the Intergovernmental Panel on Climate Change (IPCC) is framed to address this aim, as is nearly every policy plan to reduce carbon emissions — from California’s to that of the European Union (EU). This month, diplomatic talks will resume to prepare an agreement ahead of a major climate summit in Paris in 2015; again, a 2 °C warming limit is the focus.
Bold simplicity must now face reality. Politically and scientifically, the 2 °C goal is wrong-headed. Politically, it has allowed some governments to pretend that they are taking serious action to mitigate global warming, when in reality they have achieved almost nothing. Scientifically, there are better ways to measure the stress that humans are placing on the climate system than the growth of average global surface temperature — which has stalled since 1998 and is poorly coupled to entities that governments and companies can control directly.
Failure to set scientifically meaningful goals makes it hard for scientists and politicians to explain how big investments in climate protection will deliver tangible results. Some of the backlash from ‘denialists’ is partly rooted in policy-makers’ obsession with global temperatures that do not actually move in lockstep with the real dangers of climate change. New goals are needed. It is time to track an array of planetary vital signs — such as changes in the ocean heat content — that are better rooted in the scientific understanding of climate drivers and risks. Targets must also be set in terms of the many individual gases emitted by human activities and policies to mitigate those emissions.
Actionable goals have proved difficult to articulate from the beginning of climate-policy efforts. The 1992 United Nations Framework Convention on Climate Change (UNFCCC) expressed the aim as preventing “dangerous anthropogenic interference in the climate system”. Efforts to clarify the meaning of ‘dangerous’ here have proved fruitless because science offers many different answers depending on which part of the climate system is under scrutiny, and each country has a different perspective.
The 2009 and 2010 UNFCCC Conference of the Parties meetings, in Copenhagen and Cancun respectively, reframed the policy goal in more concrete terms: average global temperature. There was little scientific basis for the 2 °C figure that was adopted, but it offered a simple focal point and was familiar from earlier discussions, including those by the IPCC, EU and Group of 8 (G8) industrial countries. At the time, the 2 °C goal sounded bold and perhaps feasible.
Because it sounds firm and concerns future warming, the 2 °C target has allowed politicians to pretend that they are organizing for action when, in fact, most have done little. Pretending that they are chasing this
unattainable goal has also allowed governments to ignore the need for massive adaptation to climate change.
Second, the 2 °C goal is impractical. It is related only probabilistically to emissions and policies, so it does not tell particular governments and people what to do. In other areas of international politics, goals
have had a big effect when they have been translated into concrete, achievable actions.
Full article here (PDF) sent with press release: 2degreesC_Comment_Victor
UPDATE: Dr. Roger Pielke Sr. writes in comments:
Finally some sense is making it into these journals on the 2C threshold issue. I discussed this on my weblog several years ago also in my post
where I concluded with
“The use of the global annual-averaged surface temperature trends [should be] relegated to where it deserves to be – an historical relic.”