Buying Time for a Comprehensive Climate Policy?

The long term efficacy of global climate policy depends on the ability  to reduce human caused emission of greenhouse gasses (GHGs). However, near term success in addressing climate change could hinge on the mitigation of the four “short-lived climate pollutants” (SLCPs). Recent studies estimate that policies that reduce SLPC emissions, and therefore their atmospheric concentration, could shift warming trends into the future by “several decades”. Hu et al. estimate, in their article “Mitigation of short-lived climate pollutants slows sea-level rise”, that SLCP mitigation can also reduce cumulative sea level rise in the near term.

The cumulative human caused emission of greenhouse gasses is not only causing the current increase in global average temperatures, but raising sea levels. Even significant emissions reductions at a global level will still result in further warming. Given these enormous long term challenges, researchers, including Hu and his collaborators, look to non-CO₂ climate agents as a tool for policy makers to delay the impacts of climate change.

SLCPs are gasses and particles that contribute to climate change, but, unlike carbon dioxide, have short atmospheric life spans. The four main SLCPs analyzed by Hu et al.—methane, tropospheric ozone, hydrofluorocarbons and black carbon—can stay in the atmosphere anywhere from a week to a decade. Scientists estimate that these agents are contributing cumulatively up to 40 percent of the increase in radiative forcing. Researchers have shown that black carbon is the second most damaging climate agent (behind only CO₂) in terms of its radiative forcing effect. While past studies show that a reduction or elimination of anthropogenic SLCP emissions will decrease the rate of temperature rise, little has been done to examine the possible effect on sea level rise. Hu et al. confirm the conventional wisdom that SLCP mitigation will reduce the rate of sea level rise in the near term. They demonstrate that this type of policy can help reach politically important temporal and climactic targets. For example, the authors estimate that SLCP mitigation can reduce cumulative global sea level rise by 22 to 42 percent by 2100. However, a quarter-century delay in this policy’s implementation can increase sea level rise by nine to 11 percent, compared with a policy implemented in 2015. They also demonstrate that methane mitigation is the most effective means of limiting sea level rise in the near term.

The policy implications of this and other studies on the climatic effect of SLCP mitigation are clear: international temperature targets can be achieved in the near term through policies that emphasize short lived climate pollutant mitigation. However, long term remedies to climate concerns are still highly dependent on our ability to drastically diminish our carbon dioxide emissions.