“I was arguing with a climate change denialist who stated that the snowstorm that fell on the East Coast was proof that there was no climate warming. I countered that on the contrary, the temperature of the seas is increasing and that warmth produces humidity that goes into the clouds and saturates them with more and more water. Thus, it does prove the point that the extreme weather patterns show that climate warming is occurring. Am I right?"
Bill is correct in saying that the snowstorms that occurred on the East Coast are consistent with global warming. Although it might seem counter-intuitive, it is likely that global warming is a contributing factor in these storms.
Although many places in the eastern United States, like the DC-metro area, experienced fairly cooler temperatures this winter, the majority of the earth was warmer than average. In fact, the global average temperature in February 2010 was 1.1 °F (0.6 °C) warmer than the average over the past century, making it the sixth warmest February on record.
The red dots on the map below help visualize how much warmer the month of February was for a large portion of the world when compared to the average February temperature (from 1971-2000). The red areas indicate warmer temperatures as compared to the historic average, while the blue areas show the places that were cooler.
As the land and oceans warms, more water is evaporated into the air. And warmer air is able to hold more water than cooler air — this is why water condenses on cold windows and dew is on the ground in the morning.
Therefore, due to more water in the air in a warmer world, climate models project more precipitation to fall in general, and for storms to be more intense. Although some places in the world may experience precipitation decreases in the face of warming, like the southwest United States, climate models agree that winter precipitation in the Washington, D.C. area will increase by 10-20%.
Weather observations over the past 50 years show that the heaviest precipitation events in the northeastern United States have increased by 67%. Two of the top 10 biggest East Coast snowstorms on record occurred this winter: February 5-6, 2010 (Snowmageddon) and December 19-20, 2009 (Snowpocalypse).
In fact, three of top 10 largest snowstorms in the northeastern United States have occurred in the past decade, and more than half have occurred in the past 30 years. Observations also show that most of the United States had 71% to 80% of their snowstorms in warmer-than-normal years. The main takeaway? Warming of the planet makes certain types of weather events, like snowstorms, occur more frequently and/or intensely. Increased water vapor in the air due to warming has increased the probability of intense precipitation events hitting the East Coast.
Although many of these storms will cause heavy rain, especially in the south, when these storms occur with cooler temperatures during the winter, massive snowstorms will occur, such as what happened this winter. Case closed.
Evan Girvetz is a senior scientist from The Nature Conservancy’s Global Climate Change Program.