The reality of extreme weather, Part 1


Editor’s note: This report is the first in a two-part series chronicling recent findings about climate change. Part 2, to be published in our Jan. 19 issue, examines “What Can Be Done.” Gov. Jerry Brown requested the Scripps Institution of Oceanography meeting as part of a series of events focusing on climate change that the State of California is undertaking over the next several months with the goal of guiding contingency plans for extreme-weather disaster response.

By Lynne Friedmann

It’s not your imagination. Weather is becoming more “extreme,” leading to prolonged heat waves, heavier precipitation, severe flooding, more powerful hurricanes, and intense snowstorms. In the past 31 years, the United States has sustained 112 weather-related disasters in which damage costs reached or exceeded $1 billion, according to the National Climate Data Center.

“Sixteen of those 112 events occurred in California,” said Tony Haymet, director of Scripps Institution of Oceanography (SIO) at UCSD, during a Dec. 13 public forum on “Vulnerability and Adaptation to Extreme Events in California in the Context of a Changing Climate.”

A dozen of the country’s leading climate researchers presented new findings on the coastal impact of sea level rise, affects of extreme events on agriculture production, human health impacts, the water supply, energy demand and infrastructure, and the technical solutions as well as barriers to addressing these issues.

“Extreme events occur rarely but they affect the most people,” said SIO climate researcher Dan Cayan who organized the workshop at the behest of the governor’s office.

The human impact of extreme events go beyond property destruction to direct and indirect health that can lead to higher mortality such as the catastrophic 2003 heat wave in Europe estimated to have contributed to 30,000 deaths.

“Heat waves are expected to increase in both frequency and duration and extend over larger areas of California,” said Bart Ostro, Office of Environmental Health Hazard Assessment.

More problematic is a trend toward longer heat waves, during which mortality increases, and more humid heat waves resulting in higher nighttime temperatures. “There’s less chance for people to cool off and recover,” said Ostro.

Evening “chill hours” in which the temperature drops below 450º F are also critical for agriculture. “There are three million acres of fruit orchards with chilling requirements,” said Louise Jackson, UC Davis. “Increasing humid heat also impacts red wine grape yields.”

The long-term risks of sea level rise are of major concern because California’s development and infrastructure are concentrated along the coast. Retrospective data reveals that the majority of that building occurred during a period of calm weather from 1945 to 1980 when there was less flooding and damage from severe storms.

We are now in a period of increased storm wave damage to coastal development and infrastructure made all the worse during El Niño events.

“Major El Niños have had greater impacts than the gradual rise of sea level over the past century,” said Gary Griggs, of UC Santa Cruz. “This will continue to be the case until 2050.”

The risk posed to California from large earthquakes is well known by every citizen, but how many are aware of the other “Big One” looming – a massive, statewide winter storm. The last such megastorm occurred in the winter of 1862 and lasted 45 days. Scientists conclude from predictive modeling that future storms of this magnitude could cause more damage than even a large earthquake on the San Andreas Fault.”

Driving some of the largest precipitation events are “atmospheric rivers” (ARs), a term coined in 1990 to describe a narrow corridor of concentrated moisture in the atmosphere. ARs produce some of the largest storm extremes in California. In 2009, an atmospheric river made landfall in California depositing 15 inches of rain and resulting in flooding in the Coastal Ranges.

Projections indicate that the wettest ARs should become wetter and more frequent bringing with them higher risks of flood hazards in the Southwest; a trend increasing dramatically in the changing climate of the 21st century.

“We hope that the workshop will foster the growing partnership between scientists and decision-makers,” said Cayan, “and will heighten the resolve of the public to reduce the impacts of severe weather and environmental conditions that are driven by climate variability and climate change.”

* Note: PDFs from the individual presentations are available at Workshop videos will be posted in early January.

— Lynne Friedmann is a science writer based in Solana Beach.