How to cut climate change in half

These warming agents are as important for what they are not, as for what they are. Most significantly, they are not carbon dioxide (CO2), and they can be cut without waiting for U.S. politicians to fully recognize and address the reality of climate change and the role of CO2 from fossil fuels. Nor need we wait for the painfully slow international negotiations to produce a new global climate treaty to take effect in 2020 or beyond.
 

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The good news is that black carbon and ground-level zone can be controlled using existing technologies, and in most cases existing air pollution laws and existing institutions, at the national and regional level. HFCs can be controlled under the Montreal Protocol ozone treaty, which has already phased out nearly 100 similar chemicals and has built the capacity in every country of the world to reduce HFCs quickly.
 
Another critical distinction of these non-CO2 agents is that cutting them produces a fast response in the climate system. They remain in the atmosphere only for a very short time—from several days to three decades. Not so with CO2, some of which stays in the atmosphere for thousands of years.
 
Reducing these non-CO2 warming agents is cost effective, even in the relatively near term, in part because of the strong collateral benefits for health and agriculture. The United Nations Environment Program (UNEP) calculates that even without considering the climate benefits, most black carbon and ground-level ozone can be reduced with little or no net cost, as confirmed by long experience with clean air laws, and can save many of the millions of lives lost every year to lung and heart disease caused by these pollutants, while also significantly reducing crop damage. The price for reducing HFCs under the Montreal Protocol is pennies for an equivalent ton of CO2, a remarkable bargain in a cash-strapped world.
 
Climate vulnerable islands have formally proposed phasing down HFCs under the Montreal Protocol, with the Federated States of Micronesia leading the charge. The U.S., Mexico, and Canada followed suit, and a strong majority of 108 countries are in agreement. Because substitutes already exist for most uses, 400 major international companies have agreed to reduce HFCs starting in 2015.
 
But for the Montreal Protocol to succeed with HFCs, we need leadership from heads of government. Otherwise, the government technocrats in India and China and a few other countries will continue to shield their industries and block action on HFCs. This is what happened last November at the annual Montreal Protocol meeting, where failure to reach consensus is allowing the explosive growth of HFCs to continue.
 
Reducing these three short-lived climate pollutants may be the only way to slow warming in the next thirty to forty years.  A climate treaty that starts mandatory cuts in CO2 by 2020 will be too little and too late tokeep the world from exceeding a 2°C rise above the pre-Industrial temperature, the aspirational goal many heads of state agreed upon two years ago in Copenhagen, to prevent dangerous interference with the climate system in the next few decades.  
 
It is still essential to reduce CO2 emissions to avoid potentially catastrophic climate change in the mid- to long-term. This requires civilization to live within a carbon budget, including the U.S. This can be achieved by ensuring lower emissions of CO2 and faster removal of the CO2 that is already in the atmosphere, starting with efforts to protect and expand our forests, grasslands, and wetlands.
 
But the U.S. has an opportunity today to complement the needed cuts in CO2 by cutting these short-lived climate pollutants. The U.S. also has an opportunity to help build a strong and pragmatic global coalition dedicated to using existing technologies and existing laws and institutions to reduce this part of climate change. While the US and Mexico are working with UNEP on such an initiative, along with several other willing countries, the scale that is needed to deliver the full benefits for health, agriculture, and climate requires presidential leadership both at home and globally.
 
Perhaps most critically, focusing on non-CO2 mitigation will prove that the U.S. can act inexpensively and successfully onclimate mitigation in the near-term, countering the cynical climate nihilism of so many of our increasingly misguided, and sadly irresponsible, political leaders.   

Molina is professor, Department of Chemistry and Biochemistry, University of California, San Diego and shared the Nobel Prize in Chemistry in 1995 for his work on stratospheric ozone.
Zaelke is president, Institute for Governance and Sustainable Development, Washington, DC and Geneva and co-director, program on governance for sustainable development, Bren School of Environmental Science & Management, University of California, Santa Barbara.