The reason behind San Francisco’s unusually cold early summer this year is increasingly vulnerable to human-caused global warming.
Northern California’s temperate, Mediterranean-like weather makes it among the most sought-after regions to live in anywhere in the United States. San Francisco, specifically — a 49-square-mile city with the nation’s second-densest human population — is riddled with microclimates that backdrop gorgeous vistas. We’ve even personified our municipality’s foremost marine lawyer; may Karl The Fog live long and prosper amid an ever-warming world.
San Francisco, too, is one of the most climate crisis-resistant cities in the nation. Projected level rises won’t spell absolute disaster; urban wildfire risks will continue to remain a near nonexistent threat within SF zipcodes (sans one neighborhood); flash flooding, which is expected to only get worse with time, is eased by SF’s rolling elevation … and, by relation, creates clear residential areas where efforts need to be focused to avoid disaster.
While heatwaves and wet-bulbs — the latter atmospheric phenomenon standing as among the deadliest outcomes of the climate crisis, creating invisible “bulbs” over certain urban areas where a mix of scorching heat and high humidity render the human body unable to cool itself down properly — have plagued the United States this summer, San Francisco’s remained chill. Quite literally.
Meteorological records show that San Francisco is experiencing its coldest, gloomiest Summer since the early 1980s. Historically clear midday skies and mid-70s temperatures have been contrasted by gray overcasts and daily highs barely making it into the high-60s. Observed UV indexes have remained unusually low, as well. Even Livemore, the inland Bay Area city known for stamping record-breaking temperatures in the summer months, has stayed uncharacteristically balmy and cool.
Why is this happening? Wind patterns — specifically offshore ones that have significant importance in a region’s climate. For the San Francisco Bay Area, offshore winds create a net-cooling effect — “nature’s air conditioning,” if you will.
“That offshore wind essentially brings dry air our way rolling from inland areas to the sea, reversing our normal pattern, and it pushes our marine layer out to sea so we don’t get the moisture recovery and cool air or ‘nature’s air conditioning’ as we sometimes call it, like we normally do,” KRON4 Meteorologist Kyla Grogan tells the newsstation. However, per the meteorologist, these same offshore winds can, in unusual circumstances, create conditions rife for record-breaking heat — “offshore winds can sometimes cause San Francisco’s warmest days to occur in late summer and early fall” — toward the tail end of summer.
Because of San Francisco’s insular position on the greater peninsula, its climate is vastly more influenced by offshore wind patterns. (Moisture levels produced by passing marine layers allow San Francisco to have rich, healthy temperate forests that otherwise require heavy rainfall to thrive.) But the climate crisis is set to completely upend offshore wind patterns as we know them.
Over a decade’s worth of scientific studies and peer-reviewed observations show the North Pacific High — an anticyclone pressure system and offshore wind-producing pattern that effectively dictates San Francisco’s climate — is weakening; its waning was found to be a reason why California suffered its worst drought in over 1,000 years from 2011 to 2017.
Research conducted at the National Oceanic and Atmospheric Administration (NOAA) found a 30% reduction in the frequency of summer fog in the coast redwood region of Northern California over the 20th century. Tracking with that research (almost to an exact percentage point), a climatologist at the United States Geological Survey (USGS) published findings in 2017 that showed the San Francisco Bay Area’s fog coverage had decreased 33% over the last century. And yes, both phenomena are tied to the North Pacific High withering away.
Changes in the San Francisco Bay Area’s warming are linked to the climate crisis. San Francisco, despite its human-caused climate change reliance, has collectively warmed two degrees Fahrenheit over the past fifty years — a time frame that’s seen the offshore wind patterns affecting the city weaken and change conventions. Over the next half-century, as the climate crisis worsens, San Francisco is forecasted to see daily temperatures about four degrees higher than they are now,
The chilly, premature summer spell we’re experiencing at the moment exists with duplicity.
On the more palpable end, this meteorological outlier is a reminder of the cooler San Francisco summers common just four decades ago — years that saw half the number of days exceeding 122 Fahrenheit on the Earth’s surface. On the more dystopian end, we’re seeing, in real time, how our future survivability and quality of life within this 49-square-mile city is, truly, at the mercy of the wind.
