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The Aggregate Effect of INDCs

In preparation for the development of a new global climate agreement at COP21, the United Nations Convention on Climate Change (UNFCC) undertook a synthesis effort to understand the aggregate effect of Intended Nationally Determined Contributions (INDCs) – climate action plans submitted by countries worldwide to set out their commitments to reducing emissions beyond 2020. International Social Science Council (ISSC) World Social Science Fellow Fabiola S. Sosa-Rodriguez takes a closer look at whether the promises stack up.

On December 1 during COP21, I attended a session presenting the UNFCC’s synthesis report. The report itself was an impressive undertaking – it synthesized the aggregate effect of the 119 Intended Nationally Determined Contributions (INDCs) that 147 parties had communicated by October 2015. These parties contributed 86% of global greenhouse gas emissions in 2010.

However, at the time of the meeting, 157 INDCs had been received from 184 countries, covering 94% of the global emissions in the same year. As such, the initial results presented did not give the full picture of what member nations have promised.

The aggregate greenhouse gas emission levels in 2025 and 2030 resulting from the implementation of the INDCs were estimated and compared with global emission levels in 1990, 2000 and 2010. The report also considered whether the resulting emissions would drive the average global temperature more than 2 °C above pre-industrial levels.

The INDCs were diverse, covering different time frames. Nevertheless, most of the countries reported their actions up to 2030. Fewer included actions for the medium term (2040 or 2050).

Based on scenarios in the IPCC AR5, the estimated aggregate emissions levels from the INDCs do not fall within least-cost emissions 2⁰C scenarios by 2025 and 2030. That is to say, by the year 2025 or 2030, the efforts included in the INDCs will not have made a big enough difference for us to be certain that the temperature won’t rise above 2⁰C by the end of this century. Whether or not that target is reached strongly depends on actions taken after 2030, including whether new technologies that enable us to take carbon out of the atmosphere are available.

However, based on scenarios built using the IPCC database on historical emissions, the INDCs still leave a possibility of remaining below 2°C over the course of the 21st century. For a “likely” (66%) or higher probability of this happening, far greater emissions reduction rates and costs will be needed than those outlined in the INDCs.

To have the best chance of remaining below 2°C, it will be most effective to implement the actions outlined in the INDCs immediately. Given that greenhouse gases remain in the atmosphere a long time, maintaining high emissions over the short-term will mean that even greater reductions in emissions will be required over the longer term to meet international goals. If parties decide to wait, slowing the increase in temperature will be more difficult and more costly.

Fabiola S. Sosa-Rodriguez is a teacher and researcher at the Autonomous Metropolitan University (UAM), Mexico. She investigates how people around the world perceive and respond to risks, such as those from climate change. This story also ran on the blog of the International Social Science Council. You can see more of Future Earth's coverage of the INDCs here.