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Crazy weather: How it's linked to global warming

The story leading up to the Super Bowl was whether it would happen at all. For the previous week, Dallas, along with the rest of the Midwest and Northeast, had been buried in a blizzard that dumped record amounts of snow, closing airports, clogging highways and causing rolling power blackouts.

Commentators wondered sarcastically about what had happened to global warming. Actually, even if counter-intuitively, this major weather event was a confirmation that global warming is here, and it’s getting more serious all the time. Global warming is not just about the world getting hotter. It is also about the weather getting crazier, as Southern California also has been experiencing recently in the form of sudden temperature changes and abrupt storms.

Climate scientists, such as those at the World Meteorological Organization, caution that any individual storm, drought or flood should not be viewed as proof of anything. These events constitute weather, which is a short-term phenomenon. Climate change represents a long-term pattern, averaged over many seasons and weather events. Since data recording began in the late 1800s, it consistently documents trends in temperature, rainfall, ice melt, ocean rise and weather intensity supporting the conclusion that global warming is increasing. This correlates directly to the amount of carbon dioxide and other greenhouse gases emitted into the atmosphere by human activity, mainly from consuming carbon-based fuels. That is the fundamental point underlying the reports issued by the United Nations Intergovernmental Panel on Climate Change, the principal network of scientists studying climate change.

Any given winter may be cooler or warmer, but that just represents expected variation in a very long-term natural process. As the National Center for Atmospheric Research points out, there still will be record cold days, but fewer of them, and there will be more record highs than record lows. The trend is what matters, and the trend is one in which each of the past several decades has been warmer, on average, than the one preceding it, and the most recent decade was the warmest ever recorded. At the same time, there are cyclical conditions like El Niño and La Niña that change ocean temperatures and thereby sharply alter usual weather patterns.

Against this backdrop, it is the increase in weather intensity that underlies events like those we have been seeing throughout the country this winter. As the atmosphere warms, even slightly, it absorbs more moisture. This is accelerated by warming of the oceans and the resulting increase in evaporation. This doesn’t necessarily lead to more storms, but it does result in storms being more severe, with stronger winds and greater precipitation. In recent months, this has been exacerbated by a change in the condition known as the arctic oscillation, which has shifted cold air from the northern latitudes downward, where it has combined with moist air from the south to produce cold precipitation, that is, snow, sleet and ice. This collision of a long-term warming trend with a short-term cooling condition resulted in winter days where it was colder in the Southwest than in parts of Alaska and Canada.

At the same time, heat waves and droughts are intensified in some regions of the world, as precipitation patterns also shift. In the past year, we have seen the hottest summers ever in Russia, the heaviest monsoons ever in South Asia, the worst floods in decades in China and the greatest Arctic melting ever recorded. These extreme occurrences, coupled with extreme winter weather elsewhere, led commentator Thomas Friedman to suggest that global warming is better seen as “global weirding,” as climate change leads to increasingly severe but erratic conditions.

In the long run, as the climate continues to warm, the freakish weather events will increasingly be of the warm variety such as monsoons and hurricanes, particularly in the middle latitudes, where the ocean and atmosphere are warmer. However, especially for the short run, whenever the temperature drops into the freezing range, stormy weather will take the form of blizzards, like the ones that have been blasting the Midwest and Northeast.

The next Super Bowl will be played at an indoor stadium in Indianapolis, substantially north of Dallas. No one is predicting the weather for game day, but it would be prudent to bring a parka, or at least a raincoat, for the trip to the stadium.

Lowe is a San Diego land use and environmental lawyer. Butler is an environmental planner and adviser to the San Diego Foundation.