Global emissions cuts in line with Paris Agreement mean near-term benefits for Earth
Many countries are taking action to reduce greenhouse gas emissions consistent with Paris Agreement targets. While these efforts will lead to clear benefits in the second half of the century, the shorter-term rewards of mitigation aren’t as clear – partly because natural climate variability can mask human impact on global temperatures. Focusing their research on the effect of global emissions cuts on the next few decades, scientists supported by the EU-funded CONSTRAIN project have now also identified near-term benefits for the planet. The researchers found that efforts to keep long-term global warming at 1.5 °C above pre-industrial levels would substantially affect warming rates, even after taking natural climate variability into account. In fact, their study, which was published in the journal ‘Nature Climate Change’, shows that stringent mitigation efforts could reduce “the risk of unprecedented warming rates in the next 20 years by a factor of 13 compared with a no mitigation scenario.”
Two-pronged approach
Two approaches were used to determine if reducing emissions would have any positive effects on near-term warming rates. The first approach used simulations from the latest climate models created as part of Coupled Model Intercomparison Project Phase 6 (CMIP6), a collaborative effort involving thousands of climate researchers worldwide. The simulations were constrained based on how well they represented recent warming rates. The second approach combined thousands of simulations from a simple climate model called the Finite amplitude Impulse Response (FaIR model), with observation-based estimates on how the climate varies naturally. “The combination of these two approaches is advantageous because the CMIP6 models, while comprehensive, do not necessarily accurately represent observed internal variability, and CMIP6 was not designed to fully sample the range of parameter uncertainties that affect temperature projections,” the authors wrote in their paper. “Since FaIR is inexpensive to run, it can be used to more broadly sample uncertainty in temperature projections than individual complex climate models.” Using the two approaches, the research team ran simulations for different emissions scenarios for the next 20 years. These included efforts to keep global warming below 1.5 °C and 2 °C, as well as a “more plausible mitigation pathway” involving individual countries’ pledges – called nationally determined contributions (NDCs) – under the Paris Agreement. These pathways were then compared with two no-mitigation scenarios: a highly unlikely worst-case pathway assuming “a fivefold increase in coal use by the late twenty-first century”, and an average no-mitigation pathway, which served as the baseline. Both approaches showed “a clear benefit of strong mitigation in terms of decreasing near-term warming rates,” the study reported. For example, based on FaIR projections under the 2 °C scenario, the “warming rate is almost half that in the worst-case no mitigation scenario … and two-thirds that in the average no mitigation scenario.” Under the 1.5 °C scenario, the “warming rate is almost one-third of that in the worst-case no-mitigation scenario and just over half that in the average no-mitigation scenario.” The less ambitious NDC scenario also revealed a reduction in warming by about one third compared to the worst-case scenario and one quarter compared to the baseline. As the CONSTRAIN (Constraining uncertainty of multi decadal climate projections) researchers noted in a recent article posted on the ‘Carbon Brief’ website, “immediate and strong action on climate change can bring benefits within current lifetimes and not just far into the future.” For more information, please see: CONSTRAIN project website
Keywords
CONSTRAIN, climate, mitigation scenario, warming, emissions, Paris Agreement
