All that rain meant a bumper crop of grasses and other vegetation, which, as hot and dry conditions returned, likely contributed to a combustible mix of fuels that played a role in the severe fires that have swept California in the past two years .
These wild swings from one weather extreme to another are symptomatic of a phenomenon, variously known as “climate whiplash” or “weather whiplash,” that scientists say is likely to increase as the world warms. The intensity of wildfires these days in places like California are a symptom of climate change, experts say, but the whiplash effect poses a different set of problems for humans and natural systems. Researchers project that by the end of this century, the frequency of these abrupt transitions between wet and dry will increase by 25 percent in Northern California and as much as double in Southern California if greenhouse gasses continue to increase.
“There has been an assumption that the main thing we have to contend with climate change is increased temperatures, decreased snowpack, increased wildfire risk” on the West Coast, said Daniel Swain, a climate scientist at the University of California, Los Angeles. “Those things are still true, but there is this other dimension we will have to contend with — the increased risk of extreme flood and drought, and rapid transitions between the two.”Last year in Montecito, California, one of the state’s worst wildfires swept through the region. Weeks later, torrential rains fell on the burned ground, causing mudslides that wiped out houses and killed 21 people . In Europe this year, late spring frosts that damaged crops were followed by heavy rains that washed the crops out of the ground and flooded fields for weeks.
In the future, weather whiplash could mean an intense drought year followed by record rains that don’t allow planting or that wash fertilizer into waterways. Extreme swings between freezing and thawing can kill buds on trees, or lead to rain in northerly climes that is followed by freezing weather, forming a barrier of ice that prevents foraging animals like caribou from reaching vital winter browse.Tree ring data shows a significant increase in climate volatility in the last 60 years in Europe. The North Atlantic Jet Stream fluctuates between the Balkans to the south and Scotland to the north. Some 300 years of tree ring samples taken in both places show that the jet stream has become far more variable in the last six decades and more extreme in its positions, which results in more severe climate events and a more rapid shifting between extremes on yearly, monthly, and weekly timescales.
“The timing of the changes suggests that it’s anthropogenic,” said Valerie Trouet, who studies climate at the University of Arizona’s Laboratory of Tree-Ring Research.Experts say one cause of climate whiplash may be warming-related disruptions in the polar vortex , which in turn affects the jet stream. The vortex is a wall of wind that constantly circles the Arctic and prevents warm air from penetrating the cold regions, and cold air from moving south. When it is stable, the polar vortex produces normal, seasonal weather. But an unstable polar vortex causes abnormal and extreme weather.
Rare weather phenomenon possible