How Is Winter Possible If Climate Is Warming?

I am writing this on December 21, 2025. It is the winter solstice. For those of you that love more daylight, this is not the day for you. In fact, it is the day with the shortest duration of daylight during the year. I will explain why later. The good news, however, is daylight duration starts to increase from this point until the summer solstice. The winter solstice felt like the perfect opportunity to address one of the most common misperceptions about climate change. Many people struggle with the concept that we can simultaneously have winter weather and a warming climate, so let’s dig into it.

Climate has always changed. It will always change. There are many factors that lead to a naturally-varying climate. For example, Milankovitch orbital cycles represent changes in the shape of our orbit around the Sun; the angle of the Earth’s tilt on its axis; and the direction at which the Earth’s axis is pointing. According to NASA’s website, Serbian scientist Milutin Milankovitch proposed a hypothesis many years ago that Earth’s orbital shifts and wobbles affect how much solar radiation reached the Earth and modified climate at different time scales.

It turns out that he was right. The website noted, “These cyclical orbital movements, which became known as the Milankovitch cycles, cause variations of up to 25 percent in the amount of incoming insolation at Earth’s mid-latitudes (the areas of our planet located between about 30 and 60 degrees north and south of the equator).” The Ice Age cycles, which still exist by the way, and other climate variations are associated with them.

Since you now know that Earth’s axis tilt can change, you should take comfort in knowing that old globes in your classroom were sort of lying to you. The axial tilt is not firmly fixed. The graphic above shows the naturally-varying climate system over the past 800,000 years in terms of carbon dioxide in the atmosphere. Scientists use proxy records like trapped air in ice cores to attain such information.

The ice core graphic clearly identifies the Ice Age cycle and interglacial periods too. However, it also illustrates something alarming to climate scientists like me. The naturally-varying cycle was capped below 300 parts per million until about 1850 or so. After the Industrial Revolution, carbon dioxide emissions exploded over a relatively short period of time. Current values, according to NASA, are 430 parts per million and rising. That has led to an increase of 2.7 degrees Fahrenheit (1.5 degrees Celsius), reduced sea ice extent, changes in extreme weather, and more.

Hopefully, the previous discussion establishes that climate scientists know that climate changes naturally. However, it is not an “either/or” proposition. Grass also grows naturally, but it grows differently when a human fertilizes the lawn. Our climate is changing because of Milankovitch Cycles, El Niño/La Niña, and other well-understood processes. Yet, there is also a human-steroid on top of those things that drive changes on faster time scales.

Ok, let’s now deal with seasons. Today, we are at the winter solstice. That means in the Northern Hemisphere, Earth is tilting away from the Sun as we are orbiting it. Less direct solar energy is reaching the planet, so it tends to be cooler. The exact opposite happens at the summer solstice. This process will always be the case. Daylight duration is shorter because sunlight is incident upon the planet at a shallow angle. The Sun also has a shorter arc path across the sky. For example, at this time of year here in the South, the Sun rises in the Southeast sky and sets in the Southwest sky.

All of this means that we will always have a winter season and the associated types of weather including cold days, snowstorms, and blizzards. Tweets like, “Hey Dr. Shepherd, I had 20 inches of global warming in my yard this February in Boston,” are amusing but steeped in poor science literacy. Weather is your mood, and climate is your personality. Conditions on a given day, week, or month do not describe climate change.

Climate warming is, however, affecting winter weather. Studies have shown that less extreme cold events are happening in the U.S. In fact, I have noticed that when places like Detroit have an extreme cold snap, as it did recently, it is breaking news. Studies have also shown that there are less days below freezing too. According to a report by Carbon Brief, “There are, on average, 13 fewer days below freezing each year compared to the 1970s. Or, to put it another way, there is half a month where daily minimum temperatures are no longer cold enough for icy and snowy conditions to occur.”

The graphic above from Climate Central also shows declining snowfall over the past fifty years in the U.S. That’s bad news for snow lovers, particularly here in the South. As a child growing up in Georgia, a few snow days a year were almost guaranteed. They have been harder to come by in recent decades. In fact, we are likely to have one of our top five warmest Christmas Days on record here in Atlanta. Temperatures are expected to be in the low-to-mid seventies only a few days after the winter solstice.

Happy Holidays.