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Molina and Zaelke: Cutting Short-Lived Pollutants Can Give Quick Wins on Warming

climate change; emissions; pollution; Paris

December 7, 2015

climate change; emissions; pollution; Paris
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Policymakers should look to reductions in potent, short-lived pollutants to reduce warming faster than cuts to carbon dioxide emissions alone, write Nobel Prize-winner Mario Molina and Institute for Governance and Sustainable Development founder Durwood Zaelke in this guest post. This piece is part of our ongoing guest blog series surrounding the Paris climate talks, which has included posts on China’s political rhetoric, international climate institutions beyond the UN talks, and the links between climate and conflict in northern Nigeria.

The Paris meeting to negotiate a climate agreement is about spirit and trust as much as any specific numerical emissions target. This is because whatever the delegates are prepared to agree to in Paris will not, on its own, slow warming fast enough to keep us safe. This doesn’t mean humanity is doomed. But it does mean that negotiators need to reach an agreement that fosters a level of trust and a spirit of urgent optimism to raise our ambition after Paris, both as the Paris agreement evolves in the coming years, and, immediately, through other national and international venues. And it means that policymakers need to look beyond the national carbon dioxide (CO2) limits that are the primary focus at the Paris talks, to the highly potent short-term climate pollutants that can make a faster contribution to limiting warming.

Targets and Timelines

The nominal upper warming limit, driven by economics and politics more than science, is that temperatures should not be allowed to increase more than two degrees Celsius above pre-Industrial levels. But the impacts already being seen at the current increased warming of about one degree Celsius strongly suggest that two degrees is too risky.

At this point, the rate of the warming is becoming as important as the absolute limit. The rate is accelerating and in the process triggering self-reinforcing feedback mechanisms, where the initial warming feeds upon itself and causes still more warming. One illustration is the reduction of Arctic sea ice, a white shield that reflects incoming solar energy back to space. The warming since 1979 has reduced the ice shield enough to add another quarter as much warming as carbon dioxide caused during this period. Another example is the northward migration of permafrost, where soil that was once permanently frozen is now melting and releasing methane that causes still more warming.

At the current accelerating rate of warming, there is not enough time for ecosystems to adapt, nor to protect food production and economic development. The rate of warming needs to be reduced quickly, to slow these feedbacks, and to reduce climate impacts that are already hammering many areas of the world, including floods made worse by climate change such as those that have been destroying parts of India in recent days, and the sea-level rise and more powerful storm surges that are already damaging low-lying island and coastal countries.

Lever One: Carbon Dioxide Emissions

There are two main levers to slow climate warming. The first lever is to reduce the carbon dioxide emitted when coal and other fossil fuels are burned. To insure long-term stabilization of climate pollutants this lever should be pulled, now, as fast and as far as possible, promoting energy efficiency and clean energy sources to slow and ultimately halt carbon dioxide emissions. Forests and other natural processes that pull carbon dioxide from the atmosphere must also be protected.

But, while it is essential to pull back this carbon dioxide lever, it does not do enough to cut the current rate of warming: by mid-century an aggressive effort to reduce carbon dioxide can avoid about 0.1 degrees Celsius of warming, out of an expected two degrees Celsius or more of warming by 2050 under business as usual.

Lever Two: Short-Lived Climate Pollutants

This means policymakers need to pull back the other lever and reduce the short-lived climate pollutants, including black carbon (soot) air pollution, tropospheric ozone (the principal component of smog), methane, and hydrofluorocarbons (HFCs) — factory-made gases used in air conditioning and refrigeration. Pulling this lever can avoid about 0.6 degrees Celsius of warming by mid-century, much more than the carbon dioxide can in this same period. At the end of the century, the avoided warming from cutting the short-lived climate pollutants is 1.5 degrees Celsius compared to 1.1 degrees for carbon dioxide.

Strategies that reduce short-lived climate pollutants provide fast mitigation that can slow the rate of warming this decade.

While all climate models have uncertainties, there is little doubt about the relative speed at which these strategies can produce their results. Black carbon stays in the air for only a matter of weeks, and methane and most HFCs last only for one or two decades. In contrast, carbon dioxide can last far longer—five hundred years to thousands of years. Both the carbon dioxide and short-lived climate pollutant strategies are essential at this point—and probably still-to-be developed carbon removal strategies will be, as well.

Paris and Beyond

During his speech in Paris, President Obama noted what may be the fastest strategy available today. He first reminded the world that climate is changing faster than our solutions and that one of the enemies is cynicism—the notion that humanity can’t do anything about it. But he added that that last “month in Dubai, after years of delay, the world agreed to work together to cut the super-pollutants known as HFCs. That’s progress." And such progress should give people hope.

The strategy to phase down HFCs under the Montreal Protocol was initiated by the Federated States of Micronesia and other low-lying states, and then championed by Mexico, Canada, and the United States,  which negotiated bilateral agreements to support the HFC phase-down with China, India, Brazil, and Pakistan. The HFC phase-down will eliminate warming from one of the six main greenhouse gases, avoiding up to 0.5 degrees Celsius by the end of the century, and the equivalent of up to 100 billion tons of carbon dioxide by 2050. Parallel improvements in the efficiency of the air conditioners as manufacturers phase down HFCs refrigerants can avoid another 100 billion tons of carbon dioxide by 2050, according to a recent report by the Lawrence Berkeley National Laboratory.

With the threat of terrorism on everyone’s mind in Paris, many are asking what the connection may be with climate change.  The answer is that climate change is the envelope within which all of society’s other problems are unfolding. If the rate of warming continues to accelerate, and if impacts including sea-level rise and super storms continue with greater frequency, then the world will have to divert more and more of its scarce governance resources to conflict management, disaster relief, and the resettlement of millions of climate refugees.  The wiser and more economic course is to cut the rate of warming immediately by cutting the short-lived climate pollutants as fast as possible.

When the Paris talks conclude there must be a new level of not just trust and optimism, but also a far greater appreciation of the urgent need for speed, which must become the rallying cry going forward.

Mario Molina, who shared the Nobel Prize in Chemistry in 1995 for his work on chlorofluorocarbons in the atmosphere, teaches at the University of California, San Diego, and is President of the Mario Molina Center for Strategic Studies, in Mexico. 

Durwood J. Zaelke is the founder of the Institute for Governance and Sustainable Development, and co-directs a related program at UC Santa Barbara. 

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