Baby, It’s Cold Outside

By Philip Duffy

It’s surprising how often people ask something like “How can there be climate change when it’s cold outside today?” Evidently, we experts have not done a good job of communicating where weather comes from, and how weather is different from climate.

Today’s weather reflects the combined effects of human influences (such as greenhouse gases and particles), natural “external” influences (such as changes in the sun, and volcanoes), natural “internal” variations (such as the El Nino/La Nina cycle), and day-to-day weather changes, which are random. Any of these (including human influences) can tend to produce cooler than average or warmer than average conditions in specific times and locations. Because of these multiple influences, one or two days’ weather (such as one or two snowstorms) tell us nothing about the reality or importance of human-caused climate change, or any other factor influencing climate. This would take much more data, gathered over more locations and a much longer time.

In the same way, company stock prices are influenced by multiple factors: company earnings, activities of competitors, overall market conditions, political news, sometimes even the weather. So a one- or two-day dip in the price of a particular stock doesn’t prove that the company is unhealthy, or that a bull market is over. It takes much more data to do that. Hence, contrary to what you may have heard, “Snowmageddon” doesn’t prove or disprove the existence of climate change; it takes a lot more data (and analysis) to do that. What’s more, that data-gathering and analysis has been done, repeatedly. Unfortunately, some people don’t like the conclusion, so they try to muddy the picture.

In fact, not only does “Snowmageddon”  not disprove climate change, but some experts think climate change will bring more heavy snowstorms. How can that be? Warmer air holds more moisture, so if climate change means warmer snowstorms, then snowfall totals per storm could increase. (Single-day precipitation amounts have increased in the U.S.) Furthermore, in a warmer climate more moisture evaporates off the oceans, so overall precipitation tends to increase, even in winter. This could mean more frequent storms. So, far from disproving climate change, Snowmageddon may actually be the sort of thing that’s expected from climate change.

The first thing to say about the “snowless” Olympics is that they aren’t snowless: the high-elevation venues have record plenty of snow. The lower elevations have no (natural) snow because it has been unusually warm—there’s been plenty of precipitation: rain. Is this warmth a result of climate change? No definitive answer is possible. Certainly the Pacific Northwest region has warmed in recent decades, along with nearly everywhere else. As a result of this, average snow amounts in the region have decreased by about 20% since 1950.  But this has been a strong El Nino year, which usually means warmer than average conditions in the Pacific Northwest and elsewhere. So, between anthropogenic climate warming and El Nino, it is hardly surprising that Vancouver has experienced record warmth this winter. But this warmth doesn’t prove that climate change is real, any more than Snowmageddon proves that it’s not.

Throw another log on the fire.