Given the increasing likelihood that projected levels of carbon dioxide emissions will lead to temperature increases of 3C or more, there has been an increasing focus in recent years on the potential to reduce so-called short-lived climate pollutants (SLCPs), including black carbon, ozone, methane and hydroflourocarbons. Combined, SLCPs are estimated to as much as 40% to radiative forcing. In a new study in the journal Natural Climate Change, researchersAixue Hu et al. assess the potential impacts of various SLCP scenarios in terms of potential global sea-level rise.

Among the findings of the study:

1. In the period up to 2050, CO2 mitigation can only reduce  projected warming by about 0.1ºC, while mitigation of SLCPs can ratchet down projected temperatures by 0.6ºC, delaying 2C warming by three decades to beyond 2050. By 2100, however, CO2 mitigation becomes critical for limiting warming below 2ºC, tamp down temperature increases tenfold, to 1.1ºC;
2. By 2050, efforts to arrest SLCPs can reduce the rate of sea-level rise by 18% (and a whopping 48% in terms of thermal expansion impacts); by contrast, CO2 mitigation would have negligible impacts. By 2100, however, CO2 mitigation matters greatly, potentially reducing the rate of sea-level rise by 24%, with SLCP potentially contributing to an additional 24% reduction in this rate;
3. Mitigation of CO2 and SLCPs could reduce projected sea-level rise by 31-50% and the projected sea-level rate by 50-66% by 2100.

This article would be a good starting point for discussing the implications of controlling SLCPs. Among the questions it could generate for class discussion:

• Would efforts to substantially reduce SLCPs be cost-beneficial, and by what standards?;
• Would it prove politically and/or technologically easier to ratchet down SLCPs than carbon dioxide, why or why not?;
• Could reductions in SLCPs moot the need to consider climate geoengineering options?;
• What are the appropriate forums for regulating SLCPs?