This past week has given climate change skeptics plenty of events that seem like reasons to dispute global warming: A ship got stuck in Antarctic ice, there was a major snowstorm, and now record-low temperatures have descended on parts of the nation.
If it's so darn cold and snow-y, then how could the Earth possibly be warming?
Part of the confusion comes down to our understanding of weather and climate. People question the scientific reality of global warming because they don't know the difference.
Weather is what we see day-to-day. It explains changes in the atmosphere over short periods of time and is highly unpredictable. A sudden thunderstorm or blizzard is what we might refer to as weather.
Climate, on the hand, describes the behavior of the atmosphere over long periods of time.
Using weather (i.e a few very cold days) as evidence against global warming (i.e a decade of hotter summers) is kind of like using one man's early death to disprove the fact that, on average, life expectancies are increasing.
It's virtually impossible to tie any given weather event to global warming or not, said Duane Waliser, who specializes in climate dynamics and prediction as a chief scientist for NASA's Jet Propulsion Laboratory.
There will continue to be hot and cold extremes, but when the weather is averaged over time, a clear warming trend emerges. The past decade has been found to be the hottest since scientists started recording data in the 1880s.
But climate contrarians will still protest: "Our climate has gone through huge transitions before!" That's true. Over the past million of years the Earth has shifted between warm "interglacial" periods and cool "glacial" periods. These changes, however, occurred over long stretches of time and were caused by natural variation in the Earth's system. The changes in climate that scientists are observing today are man-made, caused by an increasing level of heat-trapping greenhouse gases in the planet. As a result, the warming of our planet is happening on a much shorter time-scale than ever before.
In fact, the whirlpool of frigid air, known as the "polar vortex," being blamed for sub-zero temperatures in the Midwest may actually be tied to warming temperatures in the Arctic. During the winter, this polar vortex normally remains locked up over the Arctic. This winter, the polar vortex is notably unstable (a pattern that was also observed in 2009-2010), possibly because of melting ice and warmer polar winters. The weakened vortex allows parts of cold Arctic air to break free, flowing into other parts of the Northern Hemisphere.
Similarly, the sea ice that trapped the Russian ship forms each winter and melts each summer. Its existence does not disprove the fact that the Antarctic's land mass is melting — a key reason sea levels are rising.