Scientists comment on 1.5 C

December 12, 2015

Dr Rachel Warren, a researcher in climate impacts and mitigation at the University of East Anglia, told Carbon Brief:  “In the 5th assessment of the IPCC, when we assessed the reasons for concern about climate change and we considered unique and threatened systems, we found that a transition from moderate to high risk to those systems occurred somewhere between 1.1-1.6C above preindustrial, whereas by 2C the risks to those systems were already high.”

Dr. Carl-Friedrich Schleussner, a scientific advisor at Climate Analytics, tackles the differences between 1.5C and 2C of warming in a new paper, which is currently under review in the journal Earth System Dynamics. He told Carbon Brief:  “Climate impacts, such as heat extremes, crop yield reductions in tropical regions and subtropical water scarcity, are projected to rise significantly between 1.5C and 2C. Under a 2C warming, annual water availability in the Mediterranean is projected to reduce by nearly 20%, a doubling compared to 1.5C.  Particularly for developing countries in the tropics, the combination of high exposure and limited capacity to adapt to rising temperatures points towards a substantial increase in risks posed by climate change” from 1.5C to 2C,” he says.  “An extra 0.5C of warming could have a big impact on our oceans, too,” Schleussner adds: “This difference in warming is very likely to be decisive for the survival of tropical coral reefs, as under 2C nearly 100% of tropical coral reefs are at risk of annual bleaching events.”

Dr Glen Peters, a senior researcher Center for International Climate and Environmental Research (CICERO) in Oslo, told Carbon Brief:  “To keep below 1.5C with a ‘likely’ chance [implies] a very, very small remaining carbon budget. If you use the IPCC’s cumulative emission budget that they published in their synthesis report, we have about 400bn tonnes of CO2 to emit [before we] go over 1.5C – and that’s starting in 2011. At current emission rates, that budget will go by about 2020 … ”

Carbon countdown Carbon Brief

How many years of current emissions would use up the IPCC’s carbon budgets for different levels of warming? Credit: Rosamund Pearce/Carbon Brief

Dr Joeri Rogelj, a research scholar at the Energy Program of the International Institute for Applied Systems Analysis (IIASA):  “From an energy system perspective and geophysics perspective, I think it is very hard to imagine that we would keep warming to below 1.5C. There is just so much inertia, and emissions would have to drop so quickly, so rapidly…  Until recently, the focus of the scientific community has been on 2C of temperature rise, or more,” says Rogelj:  “I think [1.5C] is definitely a neglected target, and it’s really a pity.  For example, of the four main scenarios of future greenhouse gas concentrations that the IPCC used in their Fifth Assessment Report (AR5), the most ambitious in terms of cutting emissions limits global average temperatures to below 2C by 2100. There isn’t one that keeps temperature rise to 1.5C,” says Rogelj, but this is set to change:  “In fact, there is a new scenario for 1.5C that has been developed for climate scientists to use. It’s definitely something that will be taking off more in the coming years.”

Here’s more from Rogelj on the “very exciting” research around 1.5C:  Meanwhile, prompted by countries’ support for a 1.5C limit, the UNFCCC has “invited” the IPCC to choose 1.5C as the topic as the next focus of a special reports.

Prof Jim Skea, the Research Council’s UK energy strategy fellow based at Imperial College London and recently elected co-chair of IPCC working group III,  said “The IPCC is now dealing with more than 20 requests for special reports over the next cycle, of which 1.5C is one. We will be thinking carefully about which ones we can do. Clearly, if that request comes from the UNFCCC [CB: which the current draft of the Paris deal does – to be delivered by 2018] it’s got to be taken extremely seriously.  I think if there’s a very clear message from UNFCCC that they want evidence on 1.5, I imagine people will gear up to it.”

Myles Allen (University of Oxford): Achieving a balance between sources and sinks of greenhouse gases in the second half of this century will require net carbon dioxide emissions to be reduced, in effect, to zero. It seems governments understand this, even if they couldn’t quite bring themselves to say so. To have a good chance of staying below 2 degrees, we need to aim for 1.5 degrees anyway, and it is sensible to acknowledge that 2 degrees itself is hardly “safe”. So, all told, a great outcome. Chapeau to French diplomacy.

Johan Rockström, Executive Director of the Stockholm Resilience Centre: This agreement is a turning point for a  world transformation within a 1.5-2°C safe operating space on Earth. Paris is a global starting point. Now we need action consistent with science to reach decarbonization by 2050 and sustainable development.

Diana Liverman, Director, Institute of the Environment, University of Arizona: The Paris agreement is a significant step in reducing the risks of anthropogenic climate change but it certainly does not eliminate them. We still face serious impacts. The current national pledges (INDCs) for emission reductions take us above 2 deg C. The agreement suggests these pledges may not be revised until 2018 by which time we will have burned even more fossil fuels with yet more commitment to warming.

This makes funding for adaptation and loss and damage from climate change even more urgent.  Both are mentioned in the agreement but there is no indication of how much of the $100 billion a year in finance promised to developing countries in the agreement will be allocated to the vulnerable to cope with the impacts of climate change. It also means that subnational, individual and private sector efforts to reduce emissions are important, especially if they contribute to emission reductions beyond national pledges.

The Intergovernmental Panel on Climate Change  is invited to provide a special report in 2018 on the impacts of global warming of 1.5 °C above pre-industrial levels and related global greenhouse gas emission pathways.  The scientific community will need to focus efforts on that right away as there is still a lot we need to understand about impacts in a world at 1.5 deg C, especially patterns of precipitation and impacts on key sectors, vulnerable groups, and regions.  And we should start studying how the planet can survive peak temperatures and then recover.

The Paris agreement preamble recognizes obligations for countries to respect, promote and consider human rights, the right to health, the rights of indigenous peoples, local communities,  migrants, children, persons with disabilities and people in vulnerable situations and the right to development, as well as gender equality, empowerment of women and intergenerational equity. This recognition of rights and particular groups is a modest win for many concerned with climate justice, but will now have to be translated into action so that mitigation, adaptation, loss and damage, finance and technology transfer explicitly consider how these policies affect, and hopefully benefit, human rights, women and other groups.

John Schellnhuber, Director of the Potsdam Institute for Climate Impact Research, on the long-term target in the draft Paris agreement (4.1): If agreed and implemented, this means bringing down greenhouse-gas emissions to net zero within a few decades. It is in line with the scientific evidence we presented of what would have to be done to limit climate risks such as weather extremes and sea-level rise. To stabilize our climate, CO2 emissions have to peak well before 2030 and should be eliminated as soon as possible after 2050. Technologies such as bio-energy and carbon capture and storage as well as afforestation can play a role to compensate for residual emissions, but cutting CO2 is key. Governments can indeed write history today, so future generations will remember the Paris summit for centuries to come.

Joeri Rogelj (IIASA, UNEP Emissions Gap Report Lead Author): The new Article 4 text is clearer in scientific terms than what we had before. Importantly, the benchmarks in terms of global peaking and global emissions reductions are consistent with the 1.5°C and 2°C temperature targets. Much remains to be done and it is encouraging to see that this agreement puts into place a process that could deliver this ambition.   Climate action has been delayed tremendously over recent decades and, even today, emissions are still increasing. Limiting warming to 1.5°C is an aspiration we will not be able to deliver if we are unable to scale up action in the next decade.   Technologies that can remove carbon dioxide from the atmosphere will become indispensable for attaining this long-term goal. The negative emissions technologies required to limit warming to 1.5°C by the end of the century are uncertain. It therefore makes scientific sense to increase climate action.   Aiming to limit warming to 1.5°C means that we need to scale up action in the near term. If some technologies do not prove viable in the longer term, then near-term reductions might well be the only way we can still manage to stay well below two degrees.

Steffen Kallbekken, Research Director (CICERO): The greatest achievement of this process is that more than 180 countries have submitted national climate policy goals. Nevertheless, this is an
historic agreement  that sends a clear signal to policy makers, businesses and investors to start the transition to a low carbon and climate resilient society.   However, estimates suggest that current pledges will result in a 2.7 and 3.7 degrees temperature increase. In order to limit climate change further, efforts must be ramped up. Importantly, countries will submit new climate policy goals every five years. Each time countries submit a new goal, the new goal must be more ambitious than the previous goal.

The Paris Agreement aims to limit warming to 2C above pre-industrial levels and to “pursue efforts to limit the temperature increase to 1.5C”. This reflects growing concern over the impacts of climate change also at levels of warming below 2 degrees. The ambitious temperature goal is, however, not matched by an equally ambitious mitigation goal.   The agreement states that countries should aim to peak their emissions as soon as possible, decline thereafter, and – in the second half of the century – balance emissions and sinks.   This does not send a clear signal about the level and timing of emission cuts, and does not provide a useful yardstick against which to measure progress. While not inconsistent with science, this does not reflect the best available science. The IPCC concluded that in order to have a likely chance of limiting warming to 2 degrees, emissions would have to be cut by 40 to 70 percent by 2050 (as compared to 2010). To reach the 1.5 degree target the emission cuts would have to be substantially larger, on the order of 70-95% by 2050.

Jim Hansen, former lead climate change scientist at NASA was interviewed in the Guardian.  His paper released in July with 16 colleagues found that Earth’s huge ice sheets, such as those found in Greenland, are melting faster than expected, meaning that even the 2C warming limit is “highly dangerous”.  The sea level could be up to five meters higher than it is today by the latter part of this century, unless greenhouse gases aren’t radically slashed, the paper states. This would inundate many of the world’s cities, including London, New York, Miami and Shanghai.  “More than half of the world’s cities of the world are at risk,” Hansen says. “If you talk to glaciologists privately they will tell you they are very concerned we are locking in much more significant sea level rises than the ice sheet models are telling us.  “The economic cost of a business as usual approach to emissions is incalculable. It will become questionable whether global governance will break down. You’re talking about hundreds of million of climate refugees from places such as Pakistan and China. We just can’t let that happen. Civilization was set up and developed with a stable, constant coastline.” Hansen believes China, the world’s largest emitter, will now step up to provide the leadership lacking from the US.  “I think we will get there because China is rational,” Hansen says. “Their leaders are mostly trained in engineering and such things, they don’t deny climate change and they have a huge incentive, which is air pollution. It’s so bad in their cities they need to move to clean energies. They realise it’s not a hoax. But they will need co-operation.”

Dr. Pablo Canziani (GCCM’s own as well as Investigador Principal Consejo Nacional de Investigaciones Cientificas y técnicas de la República Argentina, Member Academia Argentina de Ciencias del Ambiente, Member Lay Department of the Lay Department of the Argentine Conference of Bishops, Founding member Red Argentina de Ambiente y Desarrollo, Red Argentina de Laicos, Member Author Team IPCC 4th Assessement Report, which received the Nobel Peace Price 2007, Member of a number of Holy See Delegations to international environmental meetings):  The Paris agreement is reasonable as a serious first step towards a solution despite some flaws. In itself this is not bad, it depends where the next steps go and what the average citizen does to ensure that the agreement is brought to bear fruit. The Montreal Protocol in its original form was hugely insufficient to save the ozone layer.  Yet the capability to review its goals made it the only successful environmental agreement so far. Such a capability has now been added to the climate change issue. Now scientists, engineers and citizens must work to ensure the success of this process; this is just the beginning. The new phase requires not just science and technology, citizen involvement. It requires sound ethics and a new social culture, for the necessary changes in society no agreement can bring on its own.


1.5 v 2 C

Results of Structured Expert Dialogue at UNFCCC Geneva Climate Change Conference in February 2015

Emissions cap (papal) cartoon Climate risk heat map