Delegates from nearly every nation spent the last two weeks here at a United Nations climate summit struggling to chart a course to meet the extraordinarily difficult goal of net zero emissions of carbon dioxide by the year 2050.

Yet long before then, the effects of global warming could spin out of control. As the United Nations’ secretary general, António Guterres, warned in opening the meeting: “The point of no return is no longer over the horizon. It is in sight and hurtling toward us.”

Perhaps nowhere is that more true than in the Arctic. The surface air there is warming at twice the global rate and temperatures over the past five years have exceeded all previous records since 1900. This past week, the National Oceanic and Atmospheric Administration reported that the extent of Arctic summer sea ice was at its second lowest point since satellite observations began in 1979, and that average temperatures for the year ending in September were the second highest since 1900, when record-keeping began.

What will this mean? A study published in Geophysical Research Letters in June described the catastrophic consequences of losing the Arctic’s reflective summer sea ice. The ice is a great white shield that reflects incoming solar warming back to space during the long summer days of the midnight sun. Otherwise, it would be absorbed by the ocean. Losing this ice, the study explained, would be the warming equivalent of an extra 25 years of emissions at current rates, pushing us more quickly past the threshold of warming that scientists say could lead to catastrophic damage, from more intense heat waves and coastal flooding to extinctions of species and threats to food supplies.

The heating up of the Arctic is also speeding the thawing of permafrost, causing the release of more carbon dioxide and methane, a greenhouse gas 84 times more potent than carbon dioxide when measured over 20 years, along with nitrous oxide, a powerful long-lived climate pollutant.

The world needs an all-out effort to keep the Arctic ice strong. This requires cutting emissions of carbon dioxide, of course, but also attacking short-lived climate pollutants — especially black carbon, methane and tropospheric ozone. Another one, hydrofluorocarbon refrigerants, are now being phased down under an international agreement, the Montreal Protocol.

Targeting these short-term superpollutants for aggressive reduction — which, according to one study, could avoid twice as much warming by midcentury as aggressive reductions in carbon dioxide — would have a pronounced effect in the Arctic, with the potential to cut the rate of warming there by up to two-thirds.

California has shown the world how to reduce these pollutants. The state has cut black carbon emissions by more than 90 percent since the 1960s, primarily by reducing diesel emissions. California has also imposed the nation’s strongest standard for limiting methane emissions from landfills and strict regulations on refrigerants in air-conditioners and consumer products.

Other countries can build on California’s success by including plans to reduce these short-lived climate pollutants in updates to their national commitments to reduce greenhouse gas emissions, due next year under the Paris climate agreement.

The race to maintain the Arctic’s stabilizing role in the global climate means, in addition, that we need to put geoengineering into the policy mix, despite its hazards, moral or otherwise. This should start with “soft” geoengineering that can be carefully monitored as it is scaling up, and reversed if side effects become too troubling.

One example, developed by the nonprofit group Ice911, would be to cover thin, first-year ice with a type of white sand to enhance the reflectivity of the sun’s radiation and allow the ice to grow stronger. We should start field-testing this strategy immediately.

A riskier approach would be to introduce sulfates or other particles into the atmosphere to reflect solar radiation, mimicking the temperature-reducing effect of volcanic eruptions. We don’t know enough yet to employ this idea.

But we’ve reached the point where we need to understand whether it would be effective, while developing a strong governance system to manage it. The risk of losing the Arctic’s stabilizing function for the global climate now appears far greater than the risk of experimenting with geoengineering.

Save the Arctic, and we’ll have a chance to save the climate.