John Kerry and Barbara Boxer are two of the greenest members of the Senate. Jim Inhofe is the Senate's chief global warming denier. But last week—on Earth Day, no less—they came together to introduce a bill requiring the EPA to look at ways to control a dangerous pollutant that kills millions worldwide and accelerates global warming, particularly in the Arctic.

No, not carbon dioxide, which remains the main driver of worldwide climate change, but black carbon, airborne microscopic particles of soot. In the United States and Europe, black carbon comes from diesel engines and industrial smokestacks. In the developing world, the main source is primitive cooking and heating fires.

Breathing black carbon causes serious respiratory illness responsible for 1.6 million deaths a year, from the sprawling suburbs of California to the slums of Mumbai. And when it falls on ice or snow in the Arctic, it causes faster melting, accelerating tipping points like the thawing of the Greenland ice sheet. Just within the last 18 months, climate scientists have determined that black carbon could be responsible for up to half of all Arctic warming.

The good news: Since black carbon stays in the atmosphere only a short time, fast action to control it will buy time for addressing the larger issue of CO₂ emissions. Here's a video that tells everything you need to know in two minutes and 14 seconds.

On Tuesday, the eight nations of the Arctic Council, including the U.S., meet in Tromso, Norway, and black carbon is on the agenda for early action. At the meeting, Secretary Hillary Clinton's State Department team must stand up and take leadership on this issue. We've already significantly cut our domestic emissions of black carbon, although there's a still a long way to go. But the U.S. and Europe must also commit to a big increase in financial assistance to developing countries to help them switch to cleaner fuels and stoves—some of which cost less than $10 per family.

Let's be clear: Curbing black carbon is an effective strategy for fighting global warming only when combined with aggressive action against CO₂. The technologies are already available. Now we need the political will and financial support to put them in place as soon as possible. Sec. Clinton must get the message.