NEW STUDY CONFIRMS EARLY ACTION ON HFCs BRINGS SMALL BENEFITS FOR LIMITING MAXIMUM WARMING

A recent scientific paper confirms and substantiates earlier statements that early action to limit by 2030 SLCFs (short-life climate forcers, i.e. CH4, black carbon, tropospheric ozone and HFCs) brings limited benefits for limiting maximum warming temperature, and even smaller benefits in maximum 2 °C warming scenarios.

The study shows that neglecting linkages between the sources of these SLCFs and CO2 has led to an overestimation of the long-term climate benefits of controlling these pollutants in climate stabilization scenarios.

While previous studies had shown that immediate action to limit SLCFs could significantly minimize short-term climate warming, this study addresses not only short (decadal) but also long term (centennial) perspectives and assesses the impacts of SCLF and CO2 control measures in an integrated framework.

Following this approach it appears that focusing only on SLCFs bears a higher risk that CO2 stabilization is not achieved. Because of the very long environmental lifetime of CO2 (Note 1), short term CO2 mitigation is essential in order to limit climate change. These results imply that SLCF measures need to be considered complementary to, rather than a substitute for, early CO2 mitigation.

The study stresses the importance of coherently considering CO2-SLCF co-evolutions (see figure), noting that this linkage was often disregarded in earlier long-term projections, leading to overestimating the effect of SLCF measures in climate stabilization scenarios.   http://www.pnas.org/content/111/46/16325/F1.large.jpg    

 

 

Figure : Influence of SLCF-CO2 linkages under varying CO2 mitigation

(Source : Rogelj, et al., http://www.pnas.org/content/111/46/16325/F1.large.jpg

CO2 paths show a world “with CO2 mitigation” and with “no CO2 mitigation”. HFC mitigation is shown for the lower end of "business as usual" and the adoption of early measures.

Note 1 : The millennial atmospheric lifetime of anthropogenic CO2 D. Archer, V. Brovkin, Clim. Change 90, 283 (2008). http://link.springer.com/content/pdf/10.1007%2Fs10584-008-9413-1.pdf  

EFCTC Comment : Such studies reinforce the need to minimize CO2 emissions, for example by ensuring that refrigeration and thermal insulation are accomplished with the highest possible efficiency (activities in which HFCs can have a positive role in reducing an overall climate impact that includes CO2 emissions). Even so it is important to minimise all GHG emissions as appropriate, including HFCs, which can be most effectively controlled through a global cap and reduction similar to that required by the revised European F-Gas Regulation EU 517/2014.