A multi-model analysis that predicts climate scenarios depending on pre-and post-2030 emissions mitigation efforts suggests that even the most optimistic scenario is insufficient to limit global warming to 2 °C. This forward modelling approach, published in Nature Climate Change, contrasts with the traditional ‘backcast’ concept of focusing on pre-fixed climate goals and deciphering how to achieve them.
Most climate models focus on a concept known as ‘backcasting’, whereby target temperatures are determined, such as the Paris Agreement goal to limit global warming to below 2 °C, and the mitigation efforts needed to achieve them are calculated. This approach, however, does not always accurately reflect real-world climate mitigation, because efforts can vary by country, over time and by the choice of policy instrument, such as the use of carbon pricing.
Ida Sognnaes and colleagues use seven integrated assessment models to consider how variations in current and post-2030 mitigation efforts could impact global energy CO2 emissions and temperature trajectories. A wide range of emissions scenarios are predicted by 2050, yet most predict a median global warming of less than 3 °C in 2100 (median range 2.2-2.9°C). The authors find, however, that even the most optimistic mitigation scenario is insufficient to limit global warming to 2 °C. Additionally, the choice of model has a larger impact on predicting emissions than assumed mitigation efforts, emphasising the importance of cross-comparing models when predicting trajectories.
If the goal of the Paris Agreement is to be met, the authors conclude, global mitigation efforts must be enhanced, with any new pledges backed up by robust climate policies.
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