"Dropping the 2-degree limit, and with it pressure for the needed level of emission reductions, while starting a debate about a multitude of other goals is akin to doctors dithering over a critically ill patient."There has been an enormous amount of work by the scientific community on issues related to planetary boundaries and on the implications of different indicators for emission pathways beyond global mean temperature. When put together, this research has shown the 2-degree limit provides an upper bound on emissions if other key systems are to be maintained, within safe limits, a fact which, startlingly, does not come through at all in this comment, despite the space spent discussing alternative climate indicators. On this issue, the scientific literature contradicts the authors and shows clearly that including other metrics (objectives, such as reducing sea level rise, reducing ocean acidification) will increase the level of mitigation (emission reductions) needed. And last but not least, the 2-degree limit has triggered considerable political action at national, regional and global level -- indeed the present process to negotiate a new global agreement with legal force and applicable to all stems very much from the scientific “pressure” generated by the existence of this limit. If action has not been sufficient, it’s certainly not because of the limit. Many countries have indeed taken action -- or are now planning more ambitious measures; however, in overall terms, the collective effort has been fully inadequate. The world is confronted with rapidly rising emissions -- primarily exacerbated by one of the most intensive sources of CO2 emissions, coal -- exactly at a time when CO2 emissions should be decreasing. It is wrong, however, to conclude that this means the issue is lost, when the main battle lies ahead and just when the process of developing a new agreement is building momentum. It would be an act of grave irresponsibility for the 2-degree limit to be dropped. This would signal a clear deflation of pressure to reach an ambitious agreement, delegitimise the international negotiations, weaken efforts at a national level to build ambitious policies, and send a highly adverse signal to the private sector. Without the emission pressures of the 2-degree limit there would effectively be a green light for continued massive expansion of coal and other fossil fuel intensive infrastructure in the next decade. As the International Energy Agency has warned, this infrastructure could lock in warming levels of 4 degrees this century. Dropping the 2-degree limit, and with it pressure for the needed level of emission reductions, while starting a debate about a multitude of other goals is akin to doctors dithering over a critically ill patient. As in medicine, there are several indicators addressing different aspects of the vitality of the planet, but each of them would call for action if it reached a critical state. The planet’s rising temperature is a vital sign and the prognosis is clear for future warming without urgent action. What doctor would refuse to provide treatment to a patient with a body temperature exceeding 40 degrees because her blood pressure cannot be measured? Read the full rebuttal to Victor and Kennel here. Dr Bill Hare is the CEO of Climate Analytics. He is a physicist with 25 years experience in climate science, impacts and policy responses to climate change and stratospheric ozone depletion. Dr Michiel Schaeffer is director and senior scientist at Climate Analytics, a biophysicist who received his PhD in dynamic meteorology at University of Utrecht. Dr Carl-Friedrich Schleussner is a scientific adviser at Climate Analytics and a guest scientist at the Potsdam Institute of Climate Impact Research. This article was originally published on Climate Spectator.
Surprise, the Oz wrong on global warming (again)
The recent argument that the 2-degree limit cannot be translated into emission goals and budgets is unconvincing and demonstrates a deep ignorance of modern scientific developments, write climate scientists Bill Hare, Michiel Schaeffer and Carl-Friedrich Schleussner.