Researchers: California Heat Waves To Become More Humid, Stronger Along Coast

Brett Smith for — Your Universe Online

Using a “non-stationary” model that factors in the recent warming trends of the past few years, researchers from the Scripps Institution of Oceanography at UC San Diego have determined that California heat waves will become more humid and stronger in populous coastal areas.

Traditionally, California heat waves primarily affect the interior desert and valley areas that become hot during the day and both cooler and drier at night. According to study researchers Alexander Gershunov and Kristen Guirguis, their analysis and computer model data indicate that the future Golden State heat waves will be marked by greater humidity, increased nighttime temperatures, and with larger swaths of land, which include the coastal areas, being affected.

A report issued by the pair and published this week in journal Geophysical Research Letters added that both coastal and desert heat waves will become common as climate changes progresses; however the model suggests that desert heat waves may become less intense as strong average warming is projected for the interior of the state.

The study has heavy implications for those Californians living along the Pacific coast who are comforted by cooler air blowing in off the ocean.

Heat waves are stressful rare extremes defined relative to average temperatures,” said Gershunov. “We’ve known for a while that humid heat waves that are particularly hot at night are on the rise in California as the climate warms. Here, we sharpen the geographic focus to consider sub-regions of the state.”

The “non-stationary” model used by the two UC San Diego scientists acknowledges that global warming is gradually becoming commonplace. The researchers posit that a backdrop of increasing temperatures necessitates a different approach than modeling based on historical data.

Based on the hypothesis used by the researchers, the definition of heat waves would keep pace with conditions that are expected in a warmer climate.

“The advantage of using this evolving ‘non-stationary’ definition is that heat waves remain extreme events even under much warmer climate,” said Gershunov. “If they change in this evolving framework, it’s because the variance of temperature is changing, not just the average.”

The authors warned that if their models were to become reality–coastal California residents would need to significantly alter their lifestyle and the demands on society. Stronger heat in these areas would lead increased installation of air conditioning units that would in turn place additional stress on the power grid, which already experiences occasional outages.

“This trend has important human health implications for coastal California where most of the state’s population lives,” said Guirguis. “Coastal communities are acclimated to cooler mean temperatures and are not well prepared for extreme heat either physiologically or technologically through air conditioning use.”

“Populations tend to adapt to changes in their average conditions but extreme events can catch people off guard,” he added. “An increase in heat wave intensity relative to average conditions could mean much more heat-related illness during heat waves unless effective heat emergency plans are implemented.”

While this new type of heat wave would negatively impact California´s human population, the effects on animal populations and biodiversity are difficult to predict.

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