Focusing On 2100: A Risky Strategy Riddled With Equity Bias

By focusing on climate outcomes in 2100 scenarios used to inform climate policy can lead to risky strategies, potentially ignoring higher-than-acceptable mid-century warming and over emphasising negative carbon emissions in order to counter the initial “overshoot phase”. A new study published in Nature highlights the importance of focusing efforts on achieving global net-zero emissions as fast as possible and how this can leave less of a burden on future generations.

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Why is this a problem

A new study, led by Imperial College London and the International Institute for Applied Systems Analysis, published in the scientific journal Nature, problematises the focus on 2100 in climate scenarios as “a very risky strategy”. This is because focusing on scenarios built for end of the century goals brings modellers to articulate the cheapest way of hitting climate targets by 2100, which can lead to a period of “overshoot” in which global average temperatures rise above target levels for a few decades before being brought back down again. This is at the cost of reaching net zero emissions as fast as possible and remaining within a maximum temperature ceiling.

A change of focus

The paper offers alternatives to these issues by imposing a limit on peak warming and the temperature evolution thereafter, suggesting that scientists should run climate models with a different goal in mind: how to reach peak net zero emissions as fast as possible (for example by 2050), whilst keeping peak warming within the 1.5 or 2C limits.

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Global CO2 emissions in IAM pathways that limit warming to well-below 2C. Those developed according to our new scenario logic are shown with pink lines while those with the standard end-of-century focus are in dashed blue. Figure adapted from Rogelj et al. (2019) by Carbon Brief.

Bringing equity into the picture

Halting climate change is widely recognised as a question of urgency and inserting issues of equity in climate scenarios helps highlight how speeding up net zero emission objectives can play a fundamental role. Changing the focus of climate scenarios, from reaching climate goals by 2100 to focusing on net zero emissions by 2050, is just one example of how changes in basic assumptions can create substantial differences in outcomes and therefore dictate policy measures.

Euro-Mediterranean Center on #ClimateChange: integrated, multi-disciplinary and frontier research on climate science and policy.

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