Here's an interesting article on California Mediterranean-type
Climate from California Today, September 1, 2022- The Pros and Cons
The Golden State is one of only five regions in the world with a Mediterranean-type climate. |
 | | The skyline of San Francisco appears above the evening fog as the sun sets on the Marin Headlands in Sausalito.Robert Galbraith/Reuters |
|
The
allure of California has long been its almost unbelievably good
weather: predictably dry summers and pleasant, if occasionally rainy,
winters. Who wouldn’t want to escape swampy heat for this temperate
paradise? |
Our typically agreeable weather (current heat wave
notwithstanding) is officially called a Mediterranean-type climate,
defined as having cool, wet winters and dry, warm summers. Only five
places in the world share this climate: California, Central Chile,
southwestern Australia, South Africa and, of course, the Mediterranean
Basin. |
“The
California climate of having this several-month period of no rain that
coincides with the hottest time of the year is globally really weird,”
said Anna Jacobsen, plant ecology professor at California State
University, Bakersfield. “It’s a really special and kind of unique
climate cycle.” |
The
location of these five ecosystems is no accident. All are on the
western edge of continents, between 30 and 45 degrees latitude, with a
cold polar current running along the coast. Prevailing wind patterns and
the cold current effectively prevent precipitation in the summer, the
season when rainfall is most likely in the rest of the world. |
The
desirable weather that results is not only a draw for humans, but also
tends to foster a wide variety of plant and animal species. All five
regions are recognized as global biodiversity hot
spots, accounting for roughly 2 percent of the world’s land area but
nearly 20 percent of its plant species, said Dick Cameron, director of
science for land and climate programs at the Nature Conservancy in
California. |
California
in particular, with its varied topography and microclimates, is home to
more than 5,000 species of plants, roughly a quarter of which exist
only within the state. “Plants far and away are our contribution to
global biodiversity,” Cameron told me. |
But
the unique characteristics of Mediterranean-type climates also make
them more susceptible to the impacts of global warming. Because
California, for example, gets so much of its annual rainfall from a
handful of storms in the winter, even small shifts in weather conditions
can produce large effects. |
In
other words, the very characteristics that make these climates famous
(the rain-free summers) “predispose those regions to water scarcity,”
said Daniel Swain, a climate scientist at the University of California,
Los Angeles. “If the storms don’t occur during the wet season, you’re
screwed.” |
Plus, increasingly warm weather exacerbates drought conditions
by melting snowpacks and quickly evaporating water that’s stored in
lakes and the soil. California is currently in the midst of a historic
drought, and South Africa, southwestern Australia and the Mediterranean
Basin have all grappled with severe droughts in recent years too. |
These
Mediterranean-type climate ecosystems were already dry places that
global warming is making even drier, said Brandon Pratt, professor of
biology at California State University, Bakersfield. He put it this way:
“You’re already on the margin and now you leave the margin and you jump
off the cliff.” |
That’s
adding up to worse fire seasons too, experts say. These regions have
long experienced fires, and their landscapes are in many ways adapted to
burn, Swain said. |
But
the exceptionally parched land and warmer temperatures are fueling
fires that become far more destructive than what’s normal. “All of those
places are places that have big issues with wildfire.” |
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