Methodology

Under the framework of the UNFCCC, many governments have put forward proposals about how much they intend to reduce their greenhouse-gas emissions in both the near and the long term.

The aim of the Climate Action Tracker (CAT) project is to provide policy makers, civil society and the media that inform them with an up-to-date assessment of countries’ individual reduction targets and with an overview of their combined effects at the global level. The intention is to make these pledges transparent and to encourage those governments that have not yet done so to make (or increase ambition of) their targets. In addition, we assess whether countries are on track to meet their commitments with currently implemented policies.

A crucial question we answer is whether the combined effect of the individual national pledges is sufficient to ensure that global emissions are on a pathway consistent with the Paris Agreement long term temperature goal. In addition, based on a wide range of effort-sharing principles, we rate each individual country’s pledge against the range of emission levels they should aim for in the framework of a global pathway consistent with Paris.

To assess the climatic impact of all of the targets put forward by countries and thus the consistency with the Paris Agreement, we derive a global emissions pathway to 2100 which is used as input to a carbon-cycle / climate model (MAGICC6). It is run multiple times in order to obtain a probability distribution of global mean temperature and the corresponding central median estimate and corresponding exceedance probabilities. The detailed methodology of the climate model is outlined in Meinshausen et al. 2009 & 2011 and with updated parameter from Rogelj et al. 2012.

The first mandatory emission reduction targets for many of the world’s leading economies were agreed for the first commitment period (2008 to 2012) of the Kyoto Protocol, adopted in 1997. In a second commitment period, running from 2013 to 2020, a much smaller number of countries have taken on additional commitments. Under the Kyoto Protocol, developing countries are not required to reduce emissions.

Under the Copenhagen Accord of 2009 and the Cancun Agreements of 2010, many developed and developing countries communicated pledges for 2020. In the run up to the COP in Paris, countries submitted their post-2020 targets as Intended Nationally Determined Contributions (INDCs). Since then, many countries resubmitted or revised their NDCs under the Paris Agreement.

• Meinshausen M, Meinshausen N, Hare W, Raper S C B, Frieler K, Knutti R, Frame D J and Allen M R (2009) Greenhouse-gas emission targets for limiting global warming to 2 °C. Nature 458 1158–62
• Meinshausen, M., S. C. B. Raper and T. M. L. Wigley (2011) "Emulating coupled atmosphere-ocean and carbon cycle models with a simpler model, MAGICC6: Part I – Model Description and Calibration", Atmospheric Chemistry and Physics 11 1417-1456
• Rogelj, J., Meinshausen, M. & Knutti, R. (2012) Global warming under old and new scenarios using IPCC climate sensitivity range estimates. Nature Clim Change 2, 248–253. https://doi.org/10.1038/nclimate1385