2050 emissions targets to limit long-term climate change

Laxenburg, Austria – 11 January 2010. Researchers have identified critical mid-century emissions thresholds that if surpassed would make achieving particular long-term climate goals unreachable in a new study published today.

The study co-led by researchers at the National Center for Atmospheric Research (NCAR), US, and the International Institute for Applied Systems Analysis (IIASA) in Austria addresses the persistent problem of linking long-term climate policy targets to the short- and medium-term actions necessary to achieve them.

The findings, published in the latest issue of the journal Proceedings of the National Academy of Sciences, state that to effectively reach long-term climate goals it may be critical to establish targets for the mid-century. The researchers found that:

1. Under ”business as usual” assumptions, a 50% likelihood of capping the global average temperature rise at 2°C in 2100, would require the world to reduce global emissions by at least 20% by 2050 compared to 2000 levels.
2. However in another scenario with high demand for energy and land, to have a 50% chance of being at or below the 2°C requires that emissions be reduced by 50% by 2050. The researchers conclude that this would be barely feasible with current technologies.
3. Alternatively, if the world failed to curb any emissions until 2050, there would be at best only a 50% chance of limiting global warming to 3°C in 2100. And this could only be achieved, if the world reduced emissions as fast as and by as much as it could after 2050.
4. Even under favorable assumptions about future energy demand and the most stringent emissions reductions, the chances of maintaining global warming below the 2°C target by the end of the century may not be much higher than 70%.

“We knew from previous analysis that the 2°C target is difficult to achieve. We were thus surprised to find in one of our analysis that the 2°C goal was attainable from 2050 emissions that were only 20% lower than 2000 emissions. Considerably less than the 50% reduction by 2050 called for by the EU and G8 countries as well as highlighted in one of the study’s alternative scenarios”, says co-author Dr. Keywan Riahi from IIASA. “The results nevertheless clearly show that if emissions continue to rise, we may commit ourselves to potentially dangerous levels or rates of climate change. The challenge will be big, particularly if energy demand continues to be high. Then the 2°C target will be barely feasible even if the world manages to increase energy supply from zero-emissions sources to more than 60% and to halve emissions by 2050”.
                                            
The research uses computer models to understand what the minimum amount of emission reduction will be required to ensure long-term goals remain feasible and importantly what the costs of reaching these targets under various scenarios may be.

Computer models of the global energy, economic and the climate system were used to assess the relationship between possible long-term climate outcomes and the mid-century conditions on which they would presumably be based. The models incorporate factors that determine how much inertia is in the energy system, such as rates of capital stock turnover (e.g. new power plants), technology penetration, and changes to production and distribution systems. Only current technologies that have proven themselves at least at the demonstration stage, such as nuclear fission, biomass, wind power, or carbon capture and storage were considered. Geoengineering, nuclear fusion, and other technologies that have not been demonstrated as viable ways to produce energy were excluded from the study.

The information was then applied to a range of scenarios (possible future outcomes) and used to examine the balance between the costs of mitigation in the short term and the feasibility of meeting end-of-century temperature targets of either 2 or 3°C. The study explores thus the critical trade-off question of whether it is better to make higher up-front emissions reductions during the next decades or to postpone some of the emissions reductions to later when long-term goals become clearer. In other words, how much reduction is needed in the near term to ensure long-term options are still economically and technologically feasible.

“Without a sense of where emissions should be heading over the next few decades, we lack the clear signals necessary to justify investments in long-lived capital like new low-carbon power plants,” says co-author Dr. Brian O’Neill from NCAR. This study provides evidence that mid-century targets may provide the framework needed to link uncertain long-term climate goals with shorter-term actions needed to achieve these goals.

Reference: Mitigation implications of mid-century targets that preserve long-term climate policy options, O’Neill, B. C., Riahi, K., Keppo, I. Proceedings of the National Academy of Sciences

Further Information contact:
Dr. Keywan Riahi, IIASA
Tel: +43 2236 807 491 or +43 676 5512655
E-mail:  riahi@iiasa.ac.at

Dr. Brian O’Neill, National Centre for Atmospheric Research, Colorado
Tel: + 1 303 497 8118
E-mail: boneill@ucar.edu

Iain Stewart, IIASA
Tel: +43 2236 807 433 or +43 650 422 0337

About IIASA:
IIASA is an independent, interdisciplinary research institution, which specializes in natural and social scientific research methods and models valued by policy makers and the scientific community worldwide. IIASA is an international institution, with member organizations in 17 countries.

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Last updated: 02 Jul 2010