Environment ministers from dozens of countries agreed this week to speed up their efforts to reduce a class of greenhouse gases that, until now, has been largely overlooked in international climate agreements but could play a crucial role in limiting the worst effects of climate change.
They're called short-lived climate pollutants, because they linger in the atmosphere for only a short time, but they are highly potent, both in warming the planet and in their local impacts on public health. These super pollutants include methane, which escapes from oil and gas systems, agriculture and livestock; hydrofluorocarbons (HFCs), which are used in refrigeration and cooling; and black carbon, a major component of soot.
A recent IPCC report determined that the world won't succeed in limiting global warming to 1.5 degrees Celsius (2.7°F) above pre-industrial levels without reducing them.
On Sunday, the more than 60 countries that are part of the United Nations-led Climate and Clean Air Coalition agreed to cut these pollutants enough to help put the world on a pathway that rapidly reduces near-term warming while maximizing public health benefits.
"We can avoid about 0.6 degrees [Celsius (about 1°F)] of warming between now and mid-century by taking action on short-lived climate pollutants," Dan McDougall, a senior fellow at the Climate and Clean Air Coalition said. The estimate is based on a 2011 United Nations Environment Program and World Meteorological Organization assessment that looked at 16 measures to cut black carbon and methane emissions across the agriculture, energy, transportation, industry, buildings and waste management sectors.
Reducing black carbon and methane also has tremendous health benefits by improving local air quality.
"We are going to avoid the annual loss of 3 million lives prematurely because of the air pollution aspects," McDougall said of efforts to reduce black carbon and ozone-forming methane. "It's incalculable how important that is."
About 7 million people die prematurely each year from air pollution, and roughly 3 million of those premature deaths could be prevented annually by 2030 by reducing short-lived climate pollutants, according to a 2015 World Health Organization report that considered the same 16 emissions reduction measures.
Where Are Countries Promising Progress?
As countries prepare to recommit to a new round of emissions reduction targets under the Paris climate agreement in 2020, the coalition is urging countries to place a much stronger focus on short-lived climate pollutants.
Only nine countries had emissions reduction goals that specifically targeted short-lived climate pollutants in their initial "Nationally Determined Contributions" (NDCs) agreed to as part of the Paris Agreement, according to the 2018 report by the World Resources Institute.
Mexico, for example, set a goal of reducing black carbon emissions by 51 percent by 2030, and Japan planned to reduce methane emissions from rice paddies.
The United States, meanwhile, has been backsliding on some efforts to reduce short-lived climate pollutants as the Trump administration rolls back measures to reduce methane emissions from the oil and gas sector. It also has yet to sign an international agreement that would phase out the use of HFCs as refrigerants, though a few states have committed to phase out their use.
The coalition is encouraging all countries to include short-lived climate pollutants in their next round of commitments under the Paris accord and is providing technical assistance to help developing countries do so. Approximately 30 countries are ready to include short-lived climate pollutants in future Paris commitments, and the coalition hopes to expand that significantly, McDougall said.
Short Life Spans, Quick Impact
Short-lived climate pollutants remain in the atmosphere for a relatively short time, with the duration depending on the pollutant, but they are many times more potent than carbon dioxide, which can stay in the atmosphere and contribute to further warming for hundreds of years. Because of that shorter life span, cutting short-lived climate pollutants can help to quickly slow the pace of global warming while countries make deep cuts to carbon dioxide emissions.
Increases in atmospheric carbon dioxide levels continue to accelerate, and global CO2 emissions are not expected to peak until after 2030, according to a World Meteorological Organization report released Sunday for this week's UN Climate Action Summit.
The report found that countries' commitments, which have so far focused largely on reducing carbon dioxide emissions, would have to be increased fivefold from current levels of emissions reductions to limit warming to 1.5 degrees Celsius (2.7°F), a goal of the Paris accord. What's more, many countries are not meeting their current commitments.
Roughly half of the world's G20 nations, which account for around 80 percent of global greenhouse gas emissions, had fallen short of achieving their commitments under the Paris Agreement, according to a 2018 UN report. An updated draft of the UN report released Saturday found that the G20 as a whole remains off track for meeting current Paris commitment pledges as too few of the countries had made transformative climate policy commitments.
In China, which has not yet indicated how it plans to move forward on its Paris climate commitments, officials are increasingly promoting the benefits of combining efforts to address climate change and improve local air quality, efforts that increasingly include reductions in short-lived climate pollutants such as black carbon and methane, a precursor to smog.
"By killing multiple birds with one stone, co-governance of the climate, environment and development is cost-effective and achieves greater economic, social, environmental and climate benefits," Xie Zhenhua, China's Special Representative for Climate Change said at Sunday's Climate and Clean Air Assembly. "It works in China, and I am sure it will work in other countries."