Why winter doesn’t refute global warming

This Thanksgiving, I am grateful for many things, and I count critical thinking skills and basic science knowledge as part of this collection. At this time of year, it’s common to see people say things like, “They don’t seem to be talking about global warming in winter” or “If there’s a climate change, why is it snowing today? in Boston today? This probably shouldn’t be surprising because there are probably people out there who believe that Greenland is, well, green or that it’s only hot in deserts. Here’s why the winter season doesn’t disprove global warming, climate change, or whatever you want to call it.

Our climate is changing due to a combination of natural variability and man-made steroid, anthropogenic activities, to boot. Rising greenhouse gases, changing land cover and growing demand from the population have changed the climate such that weather, sea level, water cycle, agricultural productivity, infrastructure and many more are affected. Even with all of this clearly established, basic science explains why we will still overwinter even as global warming continues.

The seasons are caused by the fact that our planet is tilted on an axis of approximately 23.5 degrees (graph above). According to the Library of Congress website, “Many people think that the temperature changes because the Earth is closer to the sun in summer and farther from the sun in winter…Earth is furthest from the sun in July and closest to the sun in January! ” So what’s going on? During the summer, when the Earth is tilted towards the Sun, energy is more directly focused on Earth. In winter, the energy is more dispersed. It’s like turning on a flashlight directly on a table or at an angle. The beam is wider when the flashlight is tilted (winter). The Library of Congress website goes on to say that in winter, “….long nights and short days prevent the Earth from warming up. So, we have winter!

Incidentally, the axial tilt of the planet and changes in the way the Earth orbits the sun are responsible for many aspects of the naturally variable climate like Glacial (Ice Ages) and Interglacial periods. Take a close look at the graph above. You can see the naturally variable cycle associated with these Milankovitch cycles. Now look at the carbon dioxide levels (the dot in the upper right corner) at year 0 (roughly the present). This is far beyond the naturally variable cycle of the past 800,000 years. This graph illustrates the “and” aspects of climate change and not the “or” aspects. In other words, natural variability occurs and the burning of fossil fuels after the industrial revolution is accelerating climate change.

It is important to remember that even in 2040 or 2080, when our climate could be even warmer than today, there will still be winter. It will snow again in Boston. Cold snaps will come. The polar vortex will even still be there. Even as I write these facts, the fingerprint of global warming is apparent in winter changes. According to an analysis by Climate Central, more than 200 weather stations have experienced a decrease in winter cold snaps over the period 1970 to 2021. Cold snaps have declined by about 6 days on average since 1970.

A study in the magazine Science found that increased warming in the Arctic is causing more disruption of stratospheric polar vortices, which could lead to extreme cold events like we’ve seen in Texas. Some scientists have even suggested that blizzards could become more extreme due to climate change. For many people, these things seem counter-intuitive. The atmosphere and the Earth system are complex systems. Many things that happen do not fit our mental models. This, however, does not mean that they are hoaxes.