Such longer-term goals are crucial, but they risk distracting us from the importance of taking swift and effective action right now. If we don’t, mid-century deadlines may be too late. Former secretary of state John F. Kerry, Biden’s climate envoy, puts it this way: “Scientists tell us this decade, 2020 to 2030, must be the decade of action.” But why this decade? Because leading studies now find that fast-rising temperatures over the next 10 years have a high chance of triggering potentially uncontrollable warming. By as early as 2030, if left unchecked by new actions, global average temperatures will increase to 1.5 degrees Celsius above preindustrial levels. Temperatures that high have a strong chance of setting off tipping points in key natural systems — like melting Arctic sea ice and Siberian tundra, or destabilizing the Amazon or Gulf Stream ocean currents — causing self-reinforcing, cascading warming that will be far more difficult to stop.
If temperature rise is allowed to reach 2 degrees Celsius, nearly a dozen additional tipping points could be triggered, further destabilizing climate systems and making hard-earned emissions reductions around the world much less effective at limiting warming. These higher near-term temperatures would also cause far more massive effects in the United States and globally in the next few years: crippling heat waves, catastrophic hurricanes, storms and flooding, rampant wildfires, water shortages, crop losses, and many other brutal events that would exact an immense human price in death and displacement, as well as economic costs in the trillions.
To prevent such outcomes requires action now. Biden has proposed the most ambitious clean-energy transition in history to reduce carbon dioxide emissions, since cutting CO2 is crucial to preventing long-term climate disaster. But these aggressive reductions alone cannot adequately limit temperatures in the near term, since carbon dioxide stays in the atmosphere for decades and even centuries, continuing to warm the planet.
The best way to bring down global temperatures quickly is to lower emissions of methane, HFCs and black carbon soot — collectively known as “super pollutants.” These dissipate in the atmosphere faster, so cutting them immediately would do more to mitigate near-term climate impacts. Steep reductions in super pollutants could slash the rate of warming by half over the next 25 years. For all these reasons, the United States could aim to reduce super pollutants more deeply and quickly even than carbon dioxide. It could also urge other nations to curb super pollutants more aggressively in their Paris climate agreement pledges.
Some efforts are already underway. Under the 2016 Kigali Agreement, more than 170 countries including the United States will phase out hydrofluorocarbons, or HFCs, chemicals used in refrigeration and air conditioning, by at least 80 percent by 2047, a timetable that can be accelerated and can lead to much greater CO2 cuts by improving the energy efficiency of cooling equipment.
Many nations (especially China, India and others in the developing world) are already eager to cut black carbon soot, an aerosolized particulate that comes from burning coal and diesel fuels, wildfires and many other sources, causing millions of deaths each year while undermining the health of tens of millions more people. It also rapidly warms key areas like the Arctic, the Tibetan Plateau and major glaciers. States such as California have reduced black carbon soot by more than 90 percent in recent decades with new technologies and policies such as phasing out diesel that can be undertaken globally.
Methane emissions, which are 80 times more powerful per molecule in producing warming than CO2, come from fossil fuels, landfills, livestock and the melting of tundra, among other sources. Yet emissions from each of these can be cut deeply at low cost with existing policies, all of which the United States has begun implementing. New natural-gas production techniques and pipeline upgrades can stem “fugitive emissions” of methane while increasing yields. New technologies and feed additives can limit emissions from dairy and other cattle, while emerging technologies can capture gas leaking from landfills and turn it into valuable biogas. Finally, reducing near-term warming can head off the widespread melting of tundra, which if not stopped will cause massive new methane emissions.
There is growing support in the United States for cutting super pollutants, as reflected when Congress reached a bipartisan agreement to phase out HFCs in December. This action was backed by the chemical and cooling industries, and the Biden administration is promulgating rules to limit HFCs now. Many in American industry, including, surprisingly, some in the oil, gas and agriculture sectors, also support methane restrictions, which the Biden administration is likewise starting to regulate.
Some Americans may be skeptical about claims of special urgency, since unscientific mandates like immediately ending all fossil fuel use (or else!) have proved premature in the past. But reliable new science shows we are truly and dangerously underestimating climate risks.
In the early 1980s, scientists thought they had decades to cut chemicals that were destroying the stratospheric ozone layer, but just a few years later, when it became clear that urgent action was needed, the United States under Ronald Reagan, Britain under Margaret Thatcher and other nations produced the Montreal Protocol, which is today saving the ozone layer. Similar rapid action based on science during the coronavirus crisis has saved millions of lives and should allow us, in time, to defeat the pandemic. We will need the same sort of quick response in cutting super pollutants if we hope to stave off a wide range of climate cataclysms. The United States, once again, has a chance to lead the way.