Tomorrow, December 21, is the Winter Solstice—the shortest day of the year in the Northern Hemisphere, and the first day of our winter as measured by the planet’s journey around the Sun. Traditionally, most of the U.S. would also be well into “meteorological winter” by now, settling into several months of cold and snow. But the warming of the planet is changing our climate, leaving much of the country waiting for a winter wonderland—and that’s not a good thing. The disappearance of winter and shift in climate has negative consequences for both people and wildlife.
The first week of December saw record warmth across much of the eastern United States, with temperatures 20-30 degrees above average from Texas to Pennsylvania. Tragedy ensued when that unusual warmth collided with a strong cold front, leading to one of the most deadly and destructive tornado outbreaks ever recorded in the month of December. Just days later, another severe weather event tore through the Midwest, similarly fed by record warm temperatures.
The impacts of a winter gone missing are elsewhere as well. The Northern Hemisphere had its second-warmest November on record, and snow cover in North America last month was 220,000 square miles below average, one of the smallest areas on record. That’s bad news for businesses that depend on snow—my favorite place to cross-country ski, a spot in the West Virginia mountains that traditionally received 160 inches of snow per year—has only been open two days this season. But snow—accumulating in the mountains and melting slowly through the spring—is also a key source of water for many communities, especially in the West.
The City of Denver, Colorado, just ended its longest snowless streak in history—232 days—when a paltry 0.3 inches fell on December 10. The headwaters of the Colorado River lie within a part of the Rocky Mountains that is one of the fastest-warming regions of the country, and missing snow there translates directly into less water for the 40 million people who rely on that river. The reservoirs built to store that water and generate hydropower from its flow are at their lowest levels on record, and a water shortage has been officially declared for the communities dependent on Lake Mead.
Loss of Winter and Wildlife
Wildlife also loses out when winter goes missing. Within the Colorado River system, the ongoing severe drought affects species on land and in the water. Four of the fourteen fish species native to the system are protected under the Endangered Species Act, and drought worsened by climate change threatens the progress made to recover these species.
In addition, some species simply need the cold and snow that are increasingly lacking across the country. Take, for instance, the snowshoe hare. This northern rabbit species depends on camouflage for protection from predators, so its coat turns brown in summer and white in winter. The color change is triggered by changes in seasonal daylight, which historically is reliably correlated to the onset of snow cover in the fall and snowmelt in the spring. Now temperatures are shortening the snowy season on both ends, while the day-length cycle remains the same. Unable to blend in with their background, the chance of a hare being preyed on rises 7% for each week of color mismatch.
Warmer weather is worse for other species as well. As every snow lover knows, a few degrees of temperature marks the difference between a soft, lovely snowfall and a miserable freezing rain. This is true for some species as well. Snow cover is actually quite insulating and many species rely on it to protect their young. The chicks of the white-tailed ptarmigan, a bird that lives on the tundra high in the Rockies, are more likely to survive when the spring breeding season is snowy rather than rainy. Wolverines, the fierce but elusive largest member of the weasel family, also need snow—they dig snug dens for their young in deep snowpack.
There’s one more reason to welcome the winter season when it does arrive—cold weather is one of nature’s best ways of reducing pest populations. Ticks, for instance, survive much better in milder winters, which raises the risk of Lyme disease for people, and is also bad for other species that ticks feed on, like moose. Outbreaks of bark beetles and other pests that have overwhelmed western forests are driven, at least in part, by higher beetle survival as winters warm.
It’s not too late to prevent the disappearance of the winter wonderland that many species need. As we wrote in a blog last month, the COP26 climate negotiation made progress toward holding warming to a level that would avoid the most catastrophic impacts of climate change, but more still needs to be done. The Build Back Better Act would help the U.S. meet its commitments by accelerating renewable energy adoption and advancing nature-based solutions.