International climate policy is largely focused on reducing emissions of carbon dioxide. But even if we reduce emissions now, a proportion of CO2 will stay in the atmosphere for millennia. A faster-acting strategy is needed if we’re to avoid dangerous climate change in the short term. That’s the message from a team of experts writing in the latest issue of PNAS.
What’s needed to mitigate climate change fast, Nobel laureate Mario Molina and colleagues argue, is a focus on phasing out short-term warming agents. They pinpoint four non-CO2 gases and particles that could be regulated under existing legislation. Complementing cuts in CO2, these faster-acting mitigation strategies could “begin within 2–3 years, be substantially implemented in 5–10 years and produce a climate response within decades”, write the authors.
Their message on the need to regulate short-lived warming agents such as hydrofluorocarbons (HFCs) and black carbon is not new. To some extent Molina and co-authors reiterate the call for early action that appeared in a Nature editorial back in July. They, too, recommend that the Montreal Protocol be amended to include the phase-out of atmospheric HFCs, currently regulated under the Kyoto Protocol. But they go further in their recommendations for dealing with black carbon, suggesting possible technologies to reduce its production from cooking stoves and diesel emissions, as well as feasible institutional and political arrangements to put these technologies in place.
In addition, they call for efforts to reduce pollutant gases such as methane and nitrous oxides that ultimately increase ozone – a significant greenhouse gas – in the lower atmosphere. Regulating emissions from agriculture and transport would be crucial here. Last on their wish list is more and better biosequestration – through means such as biochar – to give carbon sinks a much-needed boost.