Freaky Weather and Global Warming

Superstorm Sandy — the Midwestern drought of 2012 — the February 2013 Midwestern blizzards — record flooding in China, Brazil and the Philippines — Europe’s deepest cold snap in 25 years — record drought in Africa. Are these extreme weather events of the past year isolated occurrences, or is there a connection? Recent studies support the view that increasing CO2 levels, global warming, and extreme weather are closely linked.

A study conducted in Antarctica by a team of scientists from the National Research Center of France, published in the February 28 2013 issue of the journal Science, suggests that CO2 increases in the past have triggered global warming periods that melted glaciers. The French team examined ice cores drilled in Antarctica over the past 30 years. They focused on ice from 20,000 to 10,000 years ago, the last period when the planet warmed naturally and glaciers melted. By measuring the concentration of nitrogen-15 isotopes throughout the ice cores, they found that carbon dioxide increase and global warming happened at virtually the same time – between 18,000 and 11,000 years ago. This confirms the position of most climate scientists that rising temperatures and CO2 increase are locked in a feedback loop. CO2 brings higher temperatures, and higher temperatures lead to more CO2 being released from deep oceans and melting permafrost, further increasing temperatures.

According to a new study by scientists at the Potsdam Institute for Climate Impact Research in Germany, to be published in the journal National Academy of Sciences, and summarized in the February 28, 2013 issue of the journal Science, “Global weather is normally influenced by waves of air that oscillate between Earth’s tropical and Arctic regions, alternately pulling warm air up from the tropics to northern climes, then bringing cold air down from the Arctic.” As a result of global warming, however, these waves are now getting stuck in their tracks. Instead of bringing cool air after a warming period, the heat just stays, sometimes for weeks or months. Normal warm-cold oscillation depends on a stable difference in temperature between a cold Arctic and warm tropics. But the Arctic is warming much faster than the rest of the world, narrowing the temperature difference and reducing the airflow between the two areas. The study suggests that these stalled wave formations explain the increasing number of extreme weather events, such as the prolonged Midwestern drought of 2012.

A new climate model developed by scientists at NOAA’s Geophysical Fluid Dynamics Laboratory and Princeton University predicts that rising CO2 levels over the next century will bring a dramatic decline in snowfall for the continental United States. Carbon dioxide content in the air has increased 40% since the mid-19th century and could double by the end of the century. The model suggests that as CO2 levels rise and global temperatures increase, less snow will fall in temperate regions. This spells trouble for areas such as the western U.S. that depend on snowmelt for fresh water. In North America, the greatest snowfall reductions will occur in the northeast, the mountains of the west, and coastal regions from Virginia to Maine. These areas are projected to get less than half the snow they currently receive. In very cold regions of the globe, however, snowfall will rise. As Arctic air warms, it holds more moisture, leading to increased precipitation in the form of snow. The Arctic, Antarctic, and the high peaks of the Himalayas, the Andes, and the Yukon will get much more snow. In other words, the unpopulated remote areas of the world will get more rain and snow, while the heavily populated regions will see less precipitation and more drought.

With the world facing this kind of climate future, it appears more urgent than ever to try forestalling it by cutting way back on CO2 emissions. That means replacing fossil fuel energy with solar, wind, and other alternative energy sources as quickly as possible. But if we shrug our shoulders and keep on burning fossil fuels, there’s every reason to believe the conditions predicted by this research will come to pass: a world with higher temperatures, less rain, less snow, more air pollution, more drought, and the occasional violent weather event thrown in. It seems worth the effort to do everything we can to hold it off.

 

Thunderstorms Warm the Planet

Summer thunderstorms can cool us off with welcome rain, but at the same time contribute to long-term global warming. The reason for this seeming contradiction, according to a study being led by Dr. Jiwen Fan of Pacific Northwest National Laboratory, lies in the way thunderstorm clouds are formed.

A building thunderhead pulls in strong updrafts of warm air rising from the ground, plus whatever natural and man-made pollutants are present in the local environment. In addition to the warm air, the updrafts suck in tiny aerosol droplets of everything from factory smoke to car exhaust to methane from cow manure. These pollutants mix with the water in the cloud when it cools and condenses to form the thunderhead. As the cool air in the cloud sinks, it becomes part of a convective cycle, sweeping into the warm updrafts coming from the ground and bringing more pollutants into the cloud.

The pollution serves to divide the natural water droplets within the thunderhead, making them too small to create rain. Instead, the droplets migrate to the top of the cloud where they freeze and absorb more water, increasing the overall size of the cloud. The research showed that these pollution-heavy clouds create stronger storms than those with little or no pollution. They spread out over a larger area and create larger anvils at the top, also acting as heat traps, gradually reflecting the stored heat back to earth. In general, the findings show that cleaner clouds produce more rain, while dirty clouds produce more heat.

The cloud research project, which is still ongoing, is a collaboration of scientists at Pacific Northwest National Laboratory in Richland, Washington, Hebrew University in Jerusalem, and the University of Maryland.