Interpretations of the Paris Agreement could lead to different temperature trends

05 April 2018

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New research published this week suggests that the interpretation of key elements of the Paris Agreement may have consequences for the permitted greenhouse gas emissions which will influence global temperature change.

The paper, published this week in Philosophical Transactions of the Royal Society by an international group of scientists incuding several Oxford Martin School researchers, is led by Jan S. Fuglestvedt, research director at CICERO, a climate research institute in Norway.

“A balance between anthropogenic emissions by sources and removals by sinks of greenhouse gases in the second half of this century is needed to achieve the target of 2 degrees, set out by the Paris Agreement" says Fuglestvedt.

The definition and calculation of “balance” is diverse, and the approach, according to the Paris Agreement, is open. The scientists explore how this balance of emissions and removal by sinks to achieve net-zero emissions can be interpreted from a scientific perspective. They also analyse the scientific implications of possible policy choices related to the balance concept and provide policymakers with an overview of issues and choices that are important to determine which approach is most appropriate in the context of the Paris Agreement.

If the widely adopted GWP100 approach is used for calculation of balance in terms of net-zero CO2-equivalent emissions and net-zero is achieved by removing as much CO2-equivalent emissions as we emit, the temperature would peak and then steadily decline. The rate of cooling will depend on the contribution of short-lived climate forcers to the overall CO2-equivalent emissions. The paper provides some numerical examples of effects of choices of method.

Further consideration for policymakers should be given to: which gases to include in the calculation of balance; should balance be understood in terms of net-zero emissions weighted across a mix of gases, or in terms of stabilization of global mean temperature or radiative forcing; and how should sinks affected by anthropogenic climate change be counted.

The paper also highlights the importance of international cooperation. When some countries underachieve balance, others will have to overachieve in order to obtain balance at a global level.

“Our paper gives an overview of issues that need interpretation. We discuss and analyse related choices that are important to implement the policies supporting the main goal of the Paris Agreement”, said Fuglestvedt.

Implications of possible interpretations of “greenhouse gas balance” in the Paris Agreement: Fuglestvedt, Jan Sigurd; Rogelj, Joeri; Millar, Richard; Allen, Myles; Boucher, Olivier; Cain, Michelle; Forster, Piers; Kriegler, Elmar; Shindell, Drew.