Year after year, the world’s nations gather to find ways to reduce carbon dioxide, the main greenhouse gas, with little meaningful progress. Frustrated by this slow pace, the United States and five other countries announced this week a modest but potentially game-changing initiative to cut three other pollutants that also contribute significantly to climate change.

The three pollutants — methane, soot (also known as black carbon) and hydrofluorocarbons — together account for about 30 percent to 40 percent of the rise in global temperatures. Unlike carbon dioxide, they do not remain in the atmosphere for a long time, but, while they are there, they drive temperatures upward.

Mainstream scientists believe that to avoid disastrous increases in the sea levels and widespread drought, the rise in global temperatures by 2050 should not exceed 2 degrees Celsius above preindustrial levels. Though cuts in carbon dioxide will also be necessary to reach that goal, curbing these three pollutants will help enormously.

Officials hope further that by tackling these pollutants they can achieve relatively quick and measurable reductions in emissions without waiting for politicians to act or the United Nations process to produce a global agreement on carbon dioxide.