Carbon dioxide is the big daddy of greenhouse gases. Making up the bulk of our emissions and staying up in the atmosphere for many centuries, whether we¡¯re successful or not at limiting global temperature rise boils down to what we do about CO2.

But it¡¯s only part of the equation in global warming. A group of lesser-discussed climate pollutants are many times more powerful than carbon dioxide and could serve as an emergency brake on near-term warming. Even better: There¡¯s reason to be cautiously optimistic.

So-called super pollutants ¡ª a group of greenhouse gases and aerosols including methane, black carbon, hydrofluorocarbons (HFCs) and tropospheric ozone ¡ª are responsible for about 45% of warming to date, with carbon dioxide responsible for the other 55%. While these emissions exist in the atmosphere for a fraction of CO2¡¯s centuries-long lifetime, they have a more potent warming effect.

Methane is the short-lived climate pollutant with the greatest impact, coming mainly from agricultural, waste and oil and gas industry sources. While methane isn¡¯t toxic in itself, it¡¯s the primary contributor to tropospheric ¡ª or ground-level ¡ª ozone. O3 is actually helpful when it¡¯s up high, 20-odd kilometers above sea level, where it filters the sun¡¯s ultraviolet radiation; but down in the lowest level of our planet¡¯s atmosphere, it wreaks havoc with our lungs and vegetation.

Black carbon ¡ª the soot that results from incomplete combustion of fossil fuels, waste and biomass ¡ª isn¡¯t a greenhouse gas, but does contribute to warming by absorbing sunlight and releasing it as heat, in the same way that urban infrastructure and asphalt roads do. As a major component of particulate matter, black carbon is bad news for our respiratory and cardiovascular systems and impedes photosynthesis in plants.

As these pollutants disappear from the atmosphere much faster than CO2, the benefits of reducing them will be realized sooner. Chris Malley, senior researcher at Stockholm Environment Institute, explained that hasty mitigation has the potential to slow down the warming expected by 2050 by as much as 0.5 degrees Celsius. But the real beauty of reducing super pollutants is the benefit to human health and food security: The Clean Air and Climate Coalition, a body launched by the United Nations Environment Program, states that it could also prevent more than 2 million premature deaths each year and avoid annual crop losses of over 50 million metric tons.

Despite their multihazardous natures, the Paris Agreement doesn¡¯t require countries to single out super pollutants in climate action plans known as nationally-determined contributions, or NDCs. As a result, many of the first NDCs didn¡¯t do so at all, simply referring to one number ¡ª CO2-equivalent, a standardized metric which converts the different...