The world’s most famous sea. Endless coastlines
and beaches. Histories and culture as rich as any on earth.
Blessed with one of our planet’s finest climates – it’s the only one with a dry
summer and wet winter. But you’d be mistaken in thinking that this
sea was the only place where such a climate existed.
Copied across four other continents, this much-desired climate is home to a very famous
state, and three very different countries far into the southern hemisphere.
But in all places, this climate just has one name, the ancient home of the summer sun – the
Mediterranean. As we continue our journey in this series
from equator to poles, it’s now time to consider the second of the three climates
occupying the temperate areas of the mid-latitudes, the Mediterranean Climate.
This climate zone has a similar temperature range to the Humid Subtropical climate that
we covered in our last episode – between 20 and 35 degrees in summer, and 5 to 20 degrees
in winter. But the most immediate and striking aspect of this climate is in its rainfall
pattern. Most world climates have their rainfall peak in the hottest months of the year, while
others have year-round rain. But only one reverses the most common pattern – only the
Mediterranean climate has a dry summer and wet winter.
To explain this unusual pattern, we have to consider both our earlier episodes on the
Tropical Monsoons, as well as the Hot Deserts. You might want to view these earlier episodes
to really get what’s about to follow. Due to the 23 degree tilt of the earth, the
convergence of trade winds in the tropics called the Doldrums shifts north and south
throughout the year. The band that lies on the poleward side of this band is usually
dry, due to extensive high pressures brought on by the downward component of the Hadley
Cell of tropical air movement. In summer, this band of high pressure is pushed further
out toward the poles, away from the Hot Deserts and into the temperate zone, causing a long
drought in this season. In winter, the Doldrums are either back at
the equator or in the other hemisphere, so the high pressure area also follows it back
that way. This allows more unstable air to return in the form of oceanic westerly winds,
which, when blown onto westward facing coasts, bring rain. This explains why the Mediterranean
climates zones lie on the western fringes of each continent.
The presence of the Mediterranean Sea at just the right latitude, allows these westerlies
to gather continual moisture as they travel east, extending the winter rain all the way
to the coasts of Lebanon and Israel at the far end of this sea. The consistency of this
climate type is well illustrated by comparing city graphs from the west to the east of the
Mediterranean. We’ll talk more about the Westerlies in
the next episode on the Oceanic climate, since they are the dominant component of weather
in those regions lying immediately poleward to the Mediterranean areas.
Because the Mediterranean summer is uniquely drought-filled, compared to all other climates
except deserts, this peak season of heat is accompanied by low humidity – what Californians
love to call “a dry heat”. As perspiration is more efficient in dry air, this heat is
a good deal more comfortable than, say, the humid summers of Georgia or Florida at the
same latitude. There are two subdivisions of the Mediterranean
climate within the Koppen Classification system both of which share the dry summers and wet
winters just described, and differing only by temperature range. The first, and more
common form is Csa, which experiences a hot summer of at least 22 degrees averaged across
the night-day cycle. This is known as the Hot Summer Mediterranean. Where the average
summer temperature is below 22 degrees, this is known as the Warm Summer Mediterranean
and has the Koppen code Csb. So where in the world do we find the Mediterranean
climate? Well, the short answer is, on every inhabited continent except Asia, which lacks
the necessary west coast. We begin in Europe, and the sea from which
this climate gains its name. To the west of the Mediterranean, out in the Atlantic, the
Azores experience warm dry summers and wet winters. Moving east onto the Iberian Peninsula
we find the cooler Csb variant of warm summers and very wet winters in the north of Portugal
and North-Western Spain. Further south, we move into the hot summer Csa variant that
Portugal’s capital of Lisbon experiences, along with most of Spain, and its capital
Madrid. In the extensive interior of the Iberian Peninsula, however, some areas are so dry
that they are classed as cool semi-desert – we’ll pick these up in a future episode.
The wet winters that define the Mediterranean type extend deep into Morocco on the North
African coast, and as we move east into the western Mediterranean basin, the entire Algerian
coast and northern Tunisia also fall within this climate. All the islands in this area
have this climate – the Balearics, Corsica, Sardinia, Sicily and Malta. The northern coast
includes the luxurious Cote d’Azur of France and this coast extends east into Italy, the
heart of Mediterranean, where the dry summer / wet winter pattern extends inland across
all western and southern provinces, including the nation’s capital, the Eternal City,
Rome. Continuing east across the Adriatic sea, much
of the coast of Croatia and all of Albania are within this climate, along with all of
Greece, including its legendary capital of Athens, and all of the Greek islands. Now
firmly into the Eastern Mediterranean basin, we reach the long coastline of Turkey, where
the wet winters and dry summers extend well inland, encompassing that country’s largest
city, the ancient metropolis of Istanbul. Finally, at the eastern end of the Mediterranean,
the coast turns south into Syria, Lebanon and Israel, including the cities of Damascus,
Beirut and Jerusalem. In North America, the entire west coast of
the United States comes under the influence of this climate, from the coasts of Washington
and Oregon in the north, with their very wet winters – this is the largest area on Earth
where we experience the warm summer Csb variant of this climate. As we head south into California,
the winters become shorter and drier, the summers longer and hotter, and we have the
classic Csa Koppen variant. An exception is San Francisco, which stays much cooler than
the surrounding area due to the proximity to cold ocean currents which often shroud
the city in fog. As we reach Southern California, and the massive conurbation of Greater Los
Angeles, fog and coastal cloud is less common, and summers hotter, especially as one moves
further inland away from the cool ocean. The last stop for this climate zone are the cities
of San Diego and Tijuana lying on each side of the US/Mexico border, before the climate
gives way to the hot desert of Baja. Moving now into the Southern Hemisphere and
South America, we encounter this climate in the cooler Csb form, worlds away from its
namesake, along the mid-coast of that longest of countries, Chile. It’s in this zone where
most of that country’s population lies, including the main port of Valparaiso, and
the capital Santiago. In Africa, south of the Namib Desert, we find
the extreme south-west of South Africa caught by the wet winter westerlies that typifies
the Csa form of the Mediterranean climate, most notably around the city of Cape Town,
famous for its dramatic backdrop of Table Mountain.
The last continent to experience this climate zone is Australia, where it brushes two parts
of the south and west facing coasts, firstly around Perth, the most isolated city in the
world, in the far west, and again, around the mid-southern city of Adelaide.
Despite its dispersal across so many continents of the globe, the Mediterranean climate is
proven as a particular and consistent type by comparing temperature and rainfall graphs
across each of these areas. Note the 6-month switch between the northern and southern hemisphere
in terms of temperature and rainfall, demonstrating the reversal of seasons on each side of the
globe. So what kind of landscapes and vegetation
do we find in the Mediterranean climate? Throughout the world, plants have adapted to survive
the drought of summer, which, occurring at the hottest time of the year, places a particular
challenge due to very high evapotranspiration rates. The Csa Hot Summer areas all have a
similar and distinctive look – one similar to a semi-arid desert, where shrubs form the
dominant plant life separated by patches of hardy grasses, bare earth and rock. A distinctive
hallmark of Mediterranean plants is the greyish-green appearance, a product of the hard, waxy layer
of leaves designed to hold in moisture during the hot summer drought.
In the cooler and wetter Csb areas, shrubland gives way to forest, and it is in such areas
within California that we find the tallest trees in the world – the sequoias or redwoods.
In Australia, the Eucalyptus tree has adapted particularly well to summer droughts and is
found throughout that continent. So successful is this family of trees in this climate that
it has been exported to other Mediterranean climate zones where it has thrived.
In terms of agriculture, the Mediterranean areas have two world famous crops. Grapes
and olives. The drinking of wine, from the fermented juice of grapes has gone on in the
Mediterranean and Near-East since ancient times, and in the last two centuries has been
exported to all other Mediterranean climate areas, as wine drinkers will know, from seeing
bottles originating from California, Chile, South Africa and Australia. The pressing of
olives to produce olive oil has also gone on since ancient times, and to this day the
oil is valued across the world for its health properties as well as its distinctive flavour.
Many other crops are grown in these regions, of course, particularly wheat and citrus fruits,
but these are more common in other climates than grapes and olives.
The Mediterranean climate type is an example where climate has directly had an impact on
humanity outside the world of agriculture. In one case, the Mediterranean itself is the
world’s most popular tourist area, seeing a third of a billion visitors per year. With
its endless coastlines and historical and cultural attractions, tourists come here in
the summer knowing that they can enjoy guaranteed sunshine and warm weather. A second example
is less obvious, and that is the world movie capital of Hollywood, California. In the early
days of movie production, when film needed bright light, production companies located
to Los Angeles where for most of the year they could be guaranteed bright sunshine and
no rain that would otherwise interrupt the shooting of movies.
So there you have it, the Mediterranean climate zone. Unique in so many ways, and if I may
say, my personal favourite, having spent over a decade living in such zones, both in Australia
and California. If you enjoyed the video, please share with
your friends and subscribe to this YouTube channel so you don’t miss future episodes.
And please leave your comments, particularly if you have experienced life in one of the
five Mediterranean climate zones around the globe.
I want to thank the many photographers and drone pilots who gave permission for their
footage to be shown this video, as well as those making their work available through
the Creative Commons. Thanks again for watching, and I’ll see
you in the next episode and the Oceanic climate zone, where these videos are made! I look
forward to seeing you then.