Cold and snowy weather – the type that has dominated this winter across much of the United States – can lead some people to question the validity of global warming. According to scientists, however, these frosty conditions are not entirely unexpected in our changing climate.
Cold temperatures are a natural part of winter. Our astronomical seasons – winter, spring, summer, and fall – are generated by the tilt of the Earth’s axis and the movement of the planet around the sun. During the winter months, our hemisphere is tilted away from the sun and receives the least amount of solar energy all year. So, even as our average global temperature goes up, winter will continue to be cold relative to the other seasons.
Although global warming will not change the tilt of the Earth’s axis, it is affecting the moisture content of our atmosphere. Increasing levels of greenhouse gases are warming the air and allowing it to hold more water vapor. As a result, when storms develop they produce more intense precipitation. In winter, that includes snow, sleet, and freezing rain when given the appropriate temperature range.
This year, we have experienced a number of arctic outbreaks from the now famous polar vortex. Each one provided a deep pool of cold air that helped produce significant snowfall throughout the eastern two-thirds of this country. While the occasional cold snap is part of the season’s natural variability, they have been lasting longer recently. Some scientists suggest this is the result of arctic amplification – a tendency for the arctic to warm more rapidly than the mid-latitudes. As the temperature difference between the two regions decreases, the jet stream slows down and takes a wavier shape. The larger the waves, the slower they move, and the weather associated with them – warm or cold – stays in place longer.
It is also important to remember that climate change is a complex global phenomenon that involves much more than what is happening in our own backyards. While it has been a brutally cold and snowy winter for many of us in the Northeast and Midwest, the western states are in the midst of a serious drought and Alaska has been experiencing record high temperatures. Beyond our borders, much of the rest of the world has been unusually warm. For example, the recent Olympic Winter Games in Sochi, Russia were the warmest in history. In the southern hemisphere, Australia sweltered through a record heat wave in early January. Experts say it is not unusual to see regional variability with climate change, but overall the Earth’s atmosphere is unequivocally warming.
This short video by the Yale Climate Forum highlights the issue of cold weather and climate change in the context of the 2013-14 winter season….
Video Credit: Yale Climate Forum and YouTube