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Cutting Short-lived Pollutant Can Halve Near-term Warming

By Michael MacCracken, The Daily Climate

Much within Amy Luers' recent Daily Climate essay on extreme weather and the climate crisis is to be commended. Indeed, cutting emissions of carbon dioxide (CO2) today won't eliminate a climate change-induced pattern favoring more severe storms and extreme weather. In advocating for emissions cuts, the climate change community has to avoid backlash from a public expecting otherwise. Adaptation and resilience-building are essential to limiting impacts.

A worker walks along a charcoal field in China.
Credit:  Nick McIntosh/flickr.

However, by aggressively cutting emissions of soot (black carbon), methane and air pollution (specifically tropospheric ozone), we can reduce the speed that the situation worsens. These compounds remain in the atmosphere only days to decades — versus centuries for the CO2 perturbation — so cutting their emissions can appreciably slow the rate of warming over the next several decades.

The different roles that long- and short-lived emissions play in climate change are important. So far, however, the international negotiating process has chosen to lump them into a single basket that assumes all greenhouse gases behave like CO2. This is like projecting the health of the Social Security trust fund by assuming everyone is a 40-year old male.

Halve Projected Warming

The importance of this distinction was made clear in a recent assessment led by atmospheric chemist Drew Shindell of NASA's Goddard Institute for Space Studies [pdf]. Organized by the United Nations Environment Programme and World Meteorological Organization, the results indicated that a moderately aggressive international emissions control program focused on the short-lived compounds could roughly halve the projected warming between the present and 2050.

Cookstoves at Colorado State University's Advanced Cookstoves Laboratory.
Credit: The Daily Climate. 

A brick kiln in India.
Credit: Peter Barker/flickr.

While slowing the warming through this approach might seem to also offer additional time for cutting CO2 emissions, this is not the case. Instead, these actions are more appropriately viewed as partially making up for earlier policy delays.

For there to be any chance to limit global warming to near 2º Celsius, which international leaders have set to limit the risk of dangerous change, emissions of all warming gases must be cut sharply over the next few decades. All nations must do their part; even if developing nation emissions went to zero tomorrow, projected developed nation emissions alone would cause too much warming (and vice-versa – we are all in this together). 

Few Taking Steps

At present, few nations are taking sufficient steps. Developed nations think it will be unproductive to act alone, so they delay. Poorer countries with lower per-capita emissions — generally in the Global South — are willing to increase efficiency, but consider emissions caps unfair because fossil-powered energy is needed to alleviate poverty. As a result, future emissions are projected to continue increasing.

To move forward, the nations with high historic and present per-capita greenhouse gas emissions — the United States, Canada, Europe, Australia, among others — need to take the lead in demonstrating that modern economies can, through efficiency gains and renewable sources of energy, prosper with low emissions. Acting alone, however, is seen as unfair. And it would not adequately address the need for emissions reductions. 

Many of the developing nations already are taking actions to cut emissions of short-lived compounds to improve health and well-being: Reducing methane emissions saves energy and helps prevent coalmine disasters. Reducing soot emissions improves efficiency, clears the air, and cuts serious health impacts. Reducing ozone pollution improves health and reduces damages to crops. Accounting for the important climate-limiting role of these actions, and adding commitments for even greater efforts, would make for a very important developing nation contribution.

Break the Logjam

Together these comparable but differentiated actions by the developed and developing nations — if aggressively pursued — could create the partnership needed to break the negotiating logjam and slow and then reverse climate change.

There is already limited movement in this direction. U.S. Secretary of State Hillary Clinton announced earlier this year that the United States would help initiate a special international effort to cut emissions of short-lived species, and a number of nations have already joined the movement.

For the United States to do its share, aggressive limits on CO2 emissions must be complemented by aggressive limits of emissions of short-lived species. In particular, the Environmental Protection Agency will need to be more aggressive in cutting short-lived emissions, particularly of methane from the oil and gas industry, and making its voluntary methane and black carbon programs mandatory.

With climate change so far along, the question now is no longer whether impacts can be avoided, but rather how bad they will become. What we do with respect to both mitigation and adaptation will control that outcome. The longer we wait, the worse the impacts and sharper the required energy transition.

The Daily Climate is a nonprofit news service covering climate change, and a Climate Central content partner.

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