After a decade of fitful talks, nearly 200 countries agreed early Saturday morning in Rwanda to the most important near-term global warming agreement ever devised.
By curtailing the rapidly growing use of hydrofluorocarbons, or HFCs, by more than 80 percent over the next 30 years, countries may have found a way to avert the worst of the worst-case global warming scenarios.
The HFC agreement should help avoid up to 0.5 degrees Celsius, or 0.9 degrees Fahrenheit, of global warming by the end of the century.
SEE ALSO:U.S. and India agree to cut the most important global warming pollutant you've never heard ofIf you've never heard of HFCs, it's probably because so far, almost all of the focus of climate negotiations has been on carbon dioxide, which we emit in far larger quantities than HFCs and which last in the air for a far longer period of time -- thousands of years versus just 14 years for some HFCs.
However, HFCs are far more effective at warming the planet that carbon dioxide is, which means that any reduction in HFC emissions are an important part of efforts to rein in global warming.
In addition, HFCs have become increasingly popular -- with emissions growing by 10 to 15 percent annually -- for use in air conditioners and refrigerators and as a substitute for the substances banned under the Montreal Protocol.
Surface temperature change from HFC emissions under business as usual scenario compared to Kigali Amendment pathway.Credit: Institute for Governance and sustainable developmentAccording to a White House fact sheet on the HFC agreement, if its goals are met it would prevent more than 80 billion metric tons of carbon dioxide equivalent by 2050, which is equal to more than a decade of carbon emissions from the entire U.S. economy. The U.S. is the second biggest emitter of carbon dioxide in the world.
Because of carbon dioxide's long atmospheric lifetime and the rapidly rising use of HFCs worldwide, scientists and activists seeking to slow global warming during the next few decades have targeted super greenhouse gases as part of a more holistic approach to the issue.
Even if we were to suddenly stop emitting carbon dioxide from power plants, the transportation sector, deforestation and other sources, the lag time due to the carbon dioxidealready built up in the air would mean the planet will continue to warm for at least decades, if not centuries.
The HFC agreement buys the planet more time by removing a near-term accelerant of global warming, with the hope that significant progress is made in cutting carbon dioxide emissions in the next decade or two under the Paris Climate Agreement, which goes into effect in November.
The HFC deal may also make it easier to constrain global warming to a lower severity, closer to the globally agreed target of 2 degrees Celsius, or 3.6 degrees Fahrenheit, compared to the preindustrial average. Without the HFC deal, soaring emissions of super greenhouse gases could have undermined the effects of carbon emissions cuts.
The legally-binding HFC agreement may help most in areas like the Arctic, where warming is already leading to widespread environmental shifts as sea ice cover plummets to record lows.
A freeze and then phase out
Under the Kigali Amendment, countries agreed to phase out the use of HFCs that are used in air conditioners and refrigerators beginning in 2019. The agreement takes the form of an amendment to the Montreal Protocol that was originally negotiated in 1988 to protect the planet's stratospheric ozone layer.
The HFC agreement calls for developed countries, such as the U.S. and European Union, to move more swiftly in cutting their use of HFCs and to provide technical support to developing nations to ensure they have cleaner alternatives.
The HFC agreement buys the planet more time by removing a near-term accelerant of global warming
The agreement marks the third milestone in international climate change diplomacy in just the past month. In late September, the Paris Climate Agreement reached its required participation threshold in order to enter into force in 2016. This is several years earlier than originally expected and unusually fast for a global United Nations agreement.
In addition, the aviation industry, a rapidly rising source of global warming pollution, agreed to a greenhouse gas emissions reduction scheme on Oct. 6.
The calving front of Sermeq Kujatdleq glacier seen from a NOAA aircraft in May, 2016.Credit: John Sonntag/NASA/Rex Shutterstock/APRegarding the HFC agreement, President Barack Obama in a statement Saturday, called the new deal "an ambitious and far-reaching solution to this looming crisis."
Under the HFC agreement, more than 100 developing countries, including China, will freeze their HFC emissions in 2024 and begin reducing them soon thereafter. Some countries, including India and Pakistan, negotiated more time to continue using HFCs, securing another four years before they need to act.
India and many other countries had previously opposed adding HFCs to the Montreal Protocol, but political pressure at home and abroad gradually moved countries to support the new deal.
World leaders and environmental groups are praising the amendment as a landmark step in addressing global warming.
Global average temperature anomalies averaged over period of 2011-2015.Credit: nasa giss“This is the biggest step we can take in the year after the Paris agreement, and is equal to stopping the entire world’s fossil-fuel CO2 emissions for more than two years," said David Doniger, the climate and clean air program director with the Natural Resources Defense Council, an environmental group, in a statement.
"While we have seen many significant successes under President Obama’s leadership in fighting climate change, this day will unquestionably be remembered as one of the most important in our effort to save the one planet we have," said EPA administrator Gina McCarthy in a statement.
陈思思
郭芯其
海滩男孩
