Cool oceans. Westerly winds. Mild winters. Mild summers. Overcast skies and rain year round. It might not seem the picture of an ideal place to live, but these lands harbour many world famous European cities, spawned not one but three global empires, and have influenced agriculture around the world more than any other. These are the lands of the Marine West Coast, the lands of the Oceanic climate.
Climates
The Mediterranean Climate
The world’s most famous sea. And to many, the world’s favourite climate. Hot dry summers and wet winters – the Mediterranean Climate blesses the ancient lands of Spain, Italy, Greece, Turkey and Israel, but is also duplicated in far off lands, including the Pacific North-West of the USA, California, Chile, South Africa and Western and South Australia.
The Humid Subtropical Climate
NEW YORK, BUENOS AIRES, MILAN, HONG KONG, SHANGHAI, TOKYO, SYDNEY – Among the world’s greatest and most exciting cities, they all have one thing in common – their climate! Defined by hot summers, cool winters and plenty of rain, the Humid Subtropical climate is home to more world cities than any other. Join me as I explore the regions of our planet that experience this climate, the dynamics behind it, and why the great cities that developed within it came to dominate the globe.
The Hot Desert Climate
THE HOTTEST PLACES on our earth. The deserts of the subtropical regions. In this video we show these parts of the world and why they are that way.
From the Mojave, Sonoran and Chihuahuan deserts of south-west United States and northern Mexico, through the arid coast of Peru, and the Gran Chaco of north-west Argentina, the Americas feature unique biomes of aridity and heat.
The largest of all deserts, the Sahara, spanning the vast northern stretches of Africa, and continuing east into the Horn of Africa and the Middle East and beyond into southern Iran, Pakistan and western India – the central continents of Earth have the greatest areas of hot and dry lands anywhere on the planet.
In southern Africa, the Namib and Kalahari deserts offer a counterpoint to their much greater northern brother.
Lastly, the majority of the “island continent” is covered by the endless plains of the Red Heart of Australia, and the Outback – the Great Sandy, Victoria and Gibson deserts.
Subtropical Highland Climate
In the mountains and valleys of the tropics, a special place awaits… An escape from the heat and humidity of the surrounding lands… Spectacular scenery, great cities, and legendary empires of old. And the place where your favourite drinks are born. Welcome to the Subtropical Highlands, and their climate of perpetual spring!
The Tropical Monsoon and Tropical Savannah Climates
The monsoons and savannahs of the tropics – home to billions of us on Planet Earth, where the tropical heat is near-constant, and where the seasons are defined by rain and drought.
From the Caribbean and Brazil, through the endless savannah of West and East Africa to southern India and South-East Asia, the tropical wet and dry climates stretch all around the equatorial zone, encompassing huge populations.
The Tropical Rainforest Climate
The Tropical Rainforest Climate, also known as the Equatorial Climate. A place of steamy jungles, and the rainforest after which the climate is named.
When you think of the equator, Indonesia and Malaysia, the Amazon river basin, Borneo, Java, Bali and the Congo of Central Africa then you are thinking correctly, for these are the places in the world where such a climate exists.
A place of no seasons, this is the tropical rainforest climate where every day is hot, and where heavy rain occurs throughout the year.
The Koppen-Geiger Climate Classification System
The Köppen-Geiger Climate Classification System
The Köppen Climate Classification System is one of the most widely used methods for categorizing climates around the world. Developed by Wladimir Köppen and later refined by Rudolf Geiger, the system combines average temperature and precipitation data to create a global climate map. This classification helps us understand not only weather patterns but also how these patterns affect ecosystems, agriculture, and human settlement.
In pretty much every area of interest, human beings love to put things into boxes. They love to categorise and classify. From artistic subjects such as music and literary genres, to science including stars, chemical elements and animals. Our planet’s climate is no exception to this. And one at first might ask why is it necessary to put a label on weather patterns from one part of the globe to another. Knowing the patterns of temperature and rainfall is important mostly for understanding how the earth can support population in that area through farming. But general knowledge of this also impacts on other areas such as tourism and migration. Regardless, humans will be humans, and in the absence of any perceived application to such knowledge will still classify, for the love of science, or to improve understanding.
Climate Graphs from a variety of Koppen zones
The primary classification of earth climate is known as the Koppen-Geiger system. It has evolved over the past 150 years to define precisely the nature of weather patterns on every part of our planet. Each of these climate zones has been covered in detail in my previous series – Secrets of World Climate, in which I show real places in each climate zone and explain why the patterns of rainfall and temperature are the way they are.
In this new series, I’ll be picking up on aspects of global and local climate that transcend these zones, case by case, in what will be known as the Climate Casebook.
The first in this series is intended as a quick reference work, summarising each of the Koppen Zones, so that in the articles that follow, anyone new to the subject can get a quick grasp of what on earth I’m talking about.
The Five Main Climate Categories
Overall, the Koppen-Geiger system has five broad categories, which describe a general pattern and roughly start at the equator and end at the pole. These are always the capital first letter of the shorthand codes that every climate zone has, and are as follows.
A – Tropical Climates
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Found near the equator.
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High temperatures year-round.
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Significant rainfall.
Subtypes:
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Af: Tropical Rainforest – rain all year.
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Am: Tropical Monsoon – very wet, with a short dry season.
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Aw/As: Tropical Savanna – distinct dry season.
B – Dry Climates
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Evaporation exceeds precipitation.
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Hot or cold deserts and semi-arid regions.
Subtypes:
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BWh: Hot Desert.
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BWk: Cold Desert.
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BSh: Hot Semi-Arid.
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BSk: Cold Semi-Arid.
C – Temperate (Mesothermal) Climates
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Moderate temperatures with defined seasons.
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Common in mid-latitudes.
Subtypes:
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Csa/Csb: Mediterranean – hot or warm dry summers.
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Cfa: Humid Subtropical – hot, humid summers.
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Cfb: Oceanic – mild, wet year-round.
D – Continental (Microthermal) Climates
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Found in interiors of continents.
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Cold winters and warm to hot summers.
Subtypes:
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Dfa/Dfb: Humid Continental – varying summer temperatures.
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Dfc/Dfd: Subarctic – very cold winters.
E – Polar Climates
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Cold all year.
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Low precipitation, mostly as snow.
Subtypes:
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ET: Tundra – at least one month above freezing.
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EF: Ice Cap – no month above freezing.
Tropical Climate Zones – Koppen Family ‘A’
Dry Climate Zones – Koppen Family ‘B’
Temperate Climate Zones – Koppen Family ‘C’
Continental Climate Zones – Koppen Family ‘D’
Polar Climate Zones – Koppen Family ‘E’
Understanding the Köppen Codes
Each climate type uses a combination of letters:
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First letter: Main climate group.
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Second letter: Precipitation pattern (e.g., dry in summer = “s”).
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Third letter (if used): Temperature variation (e.g., hot = “a”, cold = “d”).
For example:
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Csa: Hot-summer Mediterranean climate.
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Dfb: Warm-summer humid continental climate.
This system allows for precise climate identification with just two or three letters.
All Koppen codes in one place
Example of how three-digit Koppen codes work
The Köppen zones
So, armed with this knowledge, lets get straight into looking at each and every one of the Koppen zones.
A – Tropical Climates
- Af – The Tropical Rainforest, also known as the Equatorial Climate, or Selva (which is Spanish for “jungle”). Occurring only within the tropics at low elevations, the key defining characteristic of this climate is rain and hot temperatures all year round. This produces the famous rainforest that the zone is named after and the largest biodiversity on Earth.
- Am – The Tropical Monsoon. Found also exclusively within the tropics, this climate zone experiences heavy rain during part or most of the year, but also has a relatively short dry, or longer drier season, due to the shifting direction of trade winds from land to sea and vice versa.
- Aw – Tropical Savannah. A close sibling of the Tropical Monsoon, and covering much larger areas in the tropics, here the dry season is either completely dry, or is dry over a longer period. Both the Savannah and Monsoon have a mix of woodland and grassland depending upon the amount of rain and local topography. Both support enormous populations and many large cities due to the combination of heat and rainfall without the human health issues of the rainforests.
Tropical Rainforest Climate Info Sheet
Tropical Monsoon Climate Info Sheet
Tropical Savannah Climate Info Sheet
B – Dry Climates
- BWh – Hot Desert. Lying on the border of the tropics, these areas experience very little rain, and searing summer temperatures which hold the records for the highest on Earth. Little or no vegetation exists here, with only bare rock and sand as landscape.
- BSh – Hot Semi Arid. Lying next to Hot Deserts, these areas have a little more rain to support scrub-like vegetation but are still marginal in terms of sustainable human settlement.
- BWk – Cool Desert. Lying deep within the continents far from the ocean, or on the leeward side of mountains sheltering them from moist winds, these areas are as parched and desolate as the hot deserts, but experience winter temperatures that often fall below freezing point.
- BSk – Cool Semi Arid. Like the Cool Deserts only with more rain, but not enough to be classified as temperate or continental. Like their Hot Semi-Arid counterparts, they support shrub-like vegetation or hardy grasses.
Hot Desert Climate Info Sheet
Hot Semi Arid Climate Info Sheet
Cool Desert Climate Info Sheet
Cool Semi Arid Climate Info Sheet
C – Temperate (Mesothermal) Climates
- Cfa – Humid Subtropical. Lying at a similar latitude to the Hot Deserts, these areas on the eastern fringes of the continents, however, are next to warm oceans that bring in plenty of moisture. They experience tropical summers, but cool winters, and rain all year round. They are among the most important areas for human civilisation, housing enormous populations and many great world cities. Typical natural vegetation ranges from forest to swamp and grassland, but much of these areas have been given over to farming.
- Cwa – Subtropical Monsoon. A sibling of the Humid Subtropical, and found mainly in Asia at the same latitudes, this varies only in that it has a winter dry season instead of rain year round due to the presence of the Asian Monsoon.
- Csa – Hot Summer Mediterranean. Lying just above the Hot Deserts in latitude, and always on the western fringes of continents, these areas experience the hot and dry conditions of deserts in summer, but significant rain from oceanic westerly winds in winter. Natural vegetation is limited by the desert-like conditions of summer, and is typically shrub-like.
- Csb – Warm Summer Mediterranean. Always lying above their Csa siblings on the continental western coasts, these areas have warm dry summers instead of hot, and usually even heavier rainfall in winter. With less harsh winters, natural vegetation is usually in the form of coniferous forest, including the Redwoods and Sequoias of California, the tallest in the world.
- Cwb – Subtropical Highland. Occurring in tropical latitudes, the heat of the rainforest and savannah is reduced significantly through being at high altitude. The result is year round mild temperatures, with a pronounced dry season. Found mainly in Latin America, East Africa and the foothills of the Himalayas. Natural vegetation is a mix of forest and grassland.
- Cwc – Cool Subtropical Highland. At even higher altitudes in the tropics, the mild temperatures of its sibling Cwb zone gives way to noticeably chilly weather, year round. It is not common.
- Cfb – Oceanic and Subtropical Highland. One of the more confusing Koppen codes, due to an accident of nature creating very similar conditions for completely different reasons. Small upland areas near the equator, such as in Colombia and Ecuador, have this mild year round climate which also experiences rain year round. But over much larger areas in mid-latitudes, this climate exists next to western coasts, where prevailing westerlies moderate temperatures year round such that warm summers and cool winters are the norm. In both cases, limited seasonal temperature range and year round rain are its defining hallmark. Natural vegetation is mixed woodland, but these areas are heavily farmed.
- Cfc – Subpolar Oceanic. lying in certain areas higher in latitude or elevation to the Oceanic, these areas still have mild winters, but cooler summers.
Humid Subtropical Climate Info Sheet
Subtropical Monsoon Climate Info Sheet
Hot Summer Mediterranean Climate Info Sheet
Warm Summer Mediterranean Climate Info Sheet
Subtropical Highland (Dry Winter) Climate Info Sheet
Subtropical Highland (No Dry Season) Climate Info Sheet
Oceanic Climate Info Sheet
Subpolar Oceanic Climate Info Sheet
D – Continental (Microthermal) Climates
- Dfa/Dfb – The first of the six Continental climates, occurring only within the great land masses of the Northern Continents. All these climates experience high temperature ranges between summer and winter, and all have cold winters, routinely falling below freezing. These first two experience rain year round, with Dfa experiencing hot summers, and Dfb experiencing somewhat cooler but still warm summers, and are the most prevalent, occurring across wide continental areas. Natural vegetation is usually in the form of grassland, but these areas are heavily farmed.
- Dwa/Dwb – The same as Dfa/Dfb except that there is little to no rain during the winter. These occur exclusively in Eastern Asia due to the influence of the Asian Monsoon.
- Dsa/Dsb – The same as the other Continental climates, except that the summer is dry instead of winter. These areas are not common, and usually occur inward from Mediterranean climate areas.
- Dfc/Dfd – The first of the six Subarctic climates. These areas, lying to the north of and similar to the Continental climates, except winters are much, much colder. These two zones have rain or snow year round. Like all the subarctic zones, the vegetation is dominated by coniferous forest, known by the Russian word Taiga, and farming is almost non-existent. Dfc is by far the most dominant of all the Subarctic zones in terms of land area.
- Dwc/Dwd – These Subarctic zones are identical to the first two except they have dry winters – they occur only in Eastern Siberia.
- Dsc/Dsd – These very rare Subarctic zones are like the others except that the dry season occurs in summer.
Continental Climate Info Sheet
Continental Monsoon Climate Info Sheet
Dry Winter Continental Climate Info Sheet
Subarctic Climate Info Sheet
Subarctic Monsoon Climate Info Sheet
Dry Winter Subarctic Climate Info Sheet
E – Polar Climates
- ET – Tundra. Even further North than the Subarctic, the true Arctic has the treeless waste of the Tundra, where summer temperatures are just too cold to support tree growth, a situation compounded by the presence of permanently frozen soil just below the surface, known as permafrost. Only hardy grasses and shrubs survive here. Tundra also occurs in comparatively small alpine areas, and around the Straights of Magellan between South America and Antarctica.
- EF – Icecap. Below freezing point all year round, these areas produce ice sheets several kilometres thick and are confined to Greenland and Antarctica. Nothing can grow in these harshest of conditions.
Tundra Climate Info Sheet
Icecap Climate Info Sheet
So the Köppen Climate Classification System simplifies the complex world of climate into an accessible structure. By identifying global climate zones through temperature and precipitation patterns, this system allows scientists, educators, and planners to better understand the planet’s atmospheric behavior and plan accordingly.
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The Pacific North West Climate
The Pacific North West of the United States and Canada. A wonderland of nature. Epic scenery – breath-taking mountains, endless forests, windswept beaches, even volcanoes. And amazing cities that have influenced the wider world far beyond their isolated patch along the wild Pacific coast. And… it is somewhat well known for its weather too. Dominated by wet winter westerlies blowing in from the Pacific each year, its exposed coasts feature some of the highest rainfall in the world, and sport temperate rainforests.
So when I briefly touched on this region in my Secrets of World Climate Series in the Mediterranean chapter, it created some controversy. “No way that’s Mediterranean! It’s Oceanic, Maritime West Coast, like Britain and Ireland!” And, like so many others, I have to confess, I had thought the same before I did my research into that series. So I thought I should devote an article to the Curious Case of The Pacific Northwest Climate, in this, the first of the cases, in my Climate Casebook.
Location of the principal cities of the Pacific Northwest
So the wet winters of the Pacific NW are pretty well known. It’s also fairly well known that Vancouver has the mildest of all winters out of all the Canadian cities. But much fewer people know about the summers in this area.
Having lived, myself, for many years in the Mediterranean climate of Southern California and South Australia, and the Oceanic climate of Britain, I have a very strong understanding of these two climate zones borne of direct experience backed by my own research. Yes, it’s undoubtedly obvious to anyone who knows a little of geography, that those Mediterranean areas are significantly warmer than Britain, both in winter and summer. That’s one distinction. The other, still fairly well known distinction is that those Mediterranean areas have dry summers. For most of the years I lived there, I could remember most summers where it did not rain for 4, 5 or even 6 months at all. To go without rain for even one month in Britain at any time of year is unusual, which was what made the British summer of 2018, where it was sunny every day and without rain for two months, all the more remarkable.
Britain is famous for its rain, very much so, in fact. And because Seattle, Portland and Vancouver are too, and because they lie at a similar latitude facing west to an ocean, the assumption is that they must have the same climate. An assumption I also once made.
But the truth is that the Pacific NW climate is actually a hybrid of these two climates I have lived under. It has very similar winter and summer temperatures to England, but it has the wet winter and dry summer patterns of California. Oceanic temperatures meets Mediterranean rainfall patterns.
Compared to the dodgy summers of Britain, Pacific NW summers are consistently glorious affairs. Low rainfall and high sunshine hours are the norm.
Let’s start with temperature and rainfall by comparing the three main cities of the Pacific Northwest with those of Los Angeles and London. As can be seen, the Pacific NW has very similar temperatures to London, with Portland in the south being slightly warmer, and Vancouver in the north being slightly cooler. LA is hotter than all the others year round – no surprises there.
But when it comes to rainfall, here is where the eyebrows start to raise. All three Pacific Northwest cities experience less rain than London during the summer, but much heavier rain during the winter. London’s rain is consistent throughout the year, and incidentally is drier overall. London has the classic Oceanic year-round rain pattern, whereas the Pacific Northwest has distinctly wetter winters and drier summers, consistent with a Mediterranean climate like Los Angeles, albeit wetter.
Climate Graphs of Pacific Northwest cities in comparison to classic Oceanic London and Hot Summer Mediterranean Los Angeles
Comparison of sunshine hours
Equally telling is this graph comparing these same cities’ monthly sunshine hours. All three Pacific Northwest cities experience similarly low sunshine hours to London in winter, but in summer, clearer skies result in sunshine hours that are closer to that of Los Angeles, which is well known for being one of the sunniest cities in the world. In general we can see that there is a dramatic seasonal variation in sunshine in the Pacific Northwest, compared to the consistently sunny LA, and sadly rather dreary London.
This climate type was actually known to Vladimir Koppen, and he designated this type with the letters Csb – C for mild temperatures, s for dry summer, b for warm summer. It shares two letters with Los Angeles Csa, and two letters with London’s Cfb, and so, it really is a hybrid of the two.
The Pacific Northwest Climate is a hybrid of Oceanic and Hot Summer Mediterranean climates
A detailed map of Koppen zones in the region, courtesy of Adam Peterson
Mediterranean climate zones across the world include the Pacific Northwest
That’s not to say the whole region comes under this climate zone. Parts of the coast have so much rain, with some falling throughout the year, that they are in fact Oceanic, although with still a noticeable winter-summer rainfall contrast. Vancouver also fits this bill, and is on the border of Oceanic Cfb and Warm Summer Mediterranean Csb.
Ok, so the climate data doesn’t lie. The question is why does this only occur in the Pacific NW? Well, actually it does occur in a few other places of the world, such as northern Portugal, southern Chile and the coast between Adelaide and Melbourne in Australia. But these other areas are either relatively underpopulated or don’t have the global reach that the Pacific NW hubs do, so their stories of similar heavy winter rains yet warm dry and sunny summers have gone unnoticed, drowned out by the much larger and well known Csa zones of the classic Mediterranean.
Lashed by storm after storm from the Pacific in the winter, known locally as “The Pineapple Express”, the Cascade and Rocky Mountains further accentuate this rainfall from the west, dumping it on the coastal cities that lie on the western slopes. These same mountains blocks humid subtropical and continental air from bringing rains in the summer, influencing the Pacific NW high pressure to dominate the area during summer, guaranteeing relatively dry weather.
Winters see regular storms moving in off the Pacific Ocean bringing plenty of rain
In the summer, the Rockies prevent Humid Subtropical air from the east moving into the whole of the Western United States
High pressure dominates, bringing fine weather for most of the summer
And so we get very wet winters reminiscent of the Scottish and Irish coasts winter, but then summers almost as dry as those of California. It’s a bit schizoid, a cross-breed, a mongrel of a climate. But talk to the locals and they love it. Well, the summers at least. Opinion is still divided on the winters…
Climate Zone Populations
Humans. They are an interesting species aren’t they? At the time of this production, there are estimated to be 7.7 billion of them roaming around the surface, and that figure is still rising.
There are many reasons why people live in the places that they do. On the coast, or along rivers, for trade. Security in the hills, away from invaders. Occasionally, rulers arbitrarily create new capitals in the centre of their realms.
But the main determinant for human settlement is the availability of clean, fresh water. Because without it, crops cannot grow, livestock cannot be raised. Without those, there is no food. Without food, there is no population.
And what determines the availability of running water? Rainfall and temperature. Too little rain, and you have a desert. Too cold, and you have frozen ground, ice. Too much rain and heat, and you could have disease.
So climate and population are inextricably linked. And if you know a bit about climate classification, then you’ve probably wondered which climate types have the least and most populations. Well it’s time to wonder no more, because after extensive original research and tabulation this data is about to be presented, in this the latest article in my Climate Casebook.
If you’ve viewed any of my other articles then you should be familiar with the Koppen climate system, which breaks down the world into zones of climate types based on temperature and rainfall patterns. If you haven’t, then I recommend you check out my Secrets of World Climate series, or for a quick overview, this summary article.
There are 29 Koppen zones in total, but I’ve grouped most of these into the twelve more distinct categories that formed each chapter in my Secrets of World Climate series. So, let’s get right into which climate zones support what populations. You’re probably wondering which zone has the biggest population, but to keep you in suspense, we’re going to go in reverse order, starting with the most empty of human life.
At number twelve there are no surprises for guessing that the least populated climate zone is the Icecap. Since temperatures never rise above freezing, no self-sustaining settlements are possible, and so research stations make up the “population” here. The number of scientists varies depending on the season with summer being higher than winter, and the vast majority of this population numbering in the thousands is in Antarctica with typically less than one hundred on the Greenland ice sheet at any given time.
Populations in the Tundra
At number eleven, we have the next coldest zone – that of the Tundra. In these bleak, treeless lands, agriculture is impossible, and any settlements here either have to rely on supplies from outside, or on hunting wildlife. Total tundra population worldwide is estimated to be in the hundreds of thousands – a tiny, tiny fraction of the total human population. These populations are scattered worldwide with about half spread along the coasts of the Arctic and the other half concentrated in the southern tip of South America. Some of you may take issue with the inclusion of Tierra del Fuego, since it’s not true tundra in that it does not experience very cold winters like the arctic, and is in fact a slightly cooler version of the Subpolar Oceanic variety where summer temperatures rarely exceed 10°C. But it would be an omission to not mention it.
At number ten, we have the next coldest zone – the vast subarctic band that spreads across northern North America, Europe and Asia. Now we are getting into the millions in terms of population, but still less than a fifth of one percent of humans live in the vast boreal forests that experience warm summers but very cold winters here. This population is mostly found in Russia, which is to be expected as it contains the largest land area under this climate type, including the vast stretches of Siberia. There are a number of Koppen subtypes in the Subarctic. Most people live in the standard Subarctic of cold winters and year round precipitation, with a smaller fraction in the east of Asia where only light snow falls in winter, with more consistent rain in summer. A much smaller fraction live in the area of very cold winters in north-east Siberia.
Subarctic population by countries
Subarctic population by climate sub-type
Populations in the Tropical Rainforest
At number nine, and we switch from the coldest zones to one of the hottest – the year round rain and warmth of the Tropical Rainforest. With a global population of just over a quarter billion, we are at last into an area that is home to a significant percentage of total human numbers. Almost half of them live in just one country – Indonesia, with most of the others also within SE Asia, and significantly fewer numbers in South America and Africa.
At number eight and we head to the mid-latitudes, and the western fringes of the continents under the sway of maritime westerly winds – the Oceanic, characterised by rain year round and relatively mild temperatures between winter and summer. Of the two hundred and seventy million souls living in this zone, the vast majority are within the densely populated and fertile lands of northwest Europe, with the three larger countries there accounting for almost three quarters of the global Oceanic population. There are two Koppen subtypes in the Oceanic – the standard and the subpolar variety, the latter of which experiences cooler summers and is akin to a perpetual autumn. With this description it’s perhaps not surprising that only a comparatively tiny number live in this sub-zone.
Oceanic population by countries
Oceanic population by climate sub-type
Onto number seven now, and with just over 300 million people, we’re back in the tropics, but this time at the cooler elevations of upland areas, providing year round spring like temperatures in the Subtropical Highland climate. Populations are split across all continents here, with high population countries with significant upland areas like Ethiopia, Mexico, China and Colombia topping this list. Koppen listed three different variants of this climate type. Two monsoon forms separated by warm or cool temperatures which both have wet and dry seasons, and an all year warm and wet form. The warm monsoon form dominates in terms of population. By the way, when you see the word “Humid” in climate classification, it is simply designating year round rain, and is not a comment on the clamminess of air.
Subtropical Highland population by countries
Subtropical Highland population by climate sub-type
Up to a third of a billion now as we reach number six and the cool deserts. In terms of population, Central Asia, with its vast continental deserts of hot summers and cold winters, dominates, with all but two countries in this list from that area. China’s contribution comes from its north-western dry region that is part of the central Asian desert area, while most of Iran’s large population lies in this climate zone due to the high elevation of that country that would otherwise have put it in the predominately hot desert Middle East. There are two Koppen subtypes here, the semi-arid steppe, and the true cool desert. Since the latter is one of the harshest climates on earth, it’s no surprise that the steppe dominates in terms of population.
Cool Desert population by countries
Cool Desert population by climate sub-type
At number five in our countdown toward the most populous climate zone, and we reach the Mediterranean, and the copies of its unique dry summer rainfall pattern across most continents, home to almost four hundred million people. But true to form, and the actual Mediterranean dominates the population list with only the extensive dry summer pattern of the western coast of the United States providing numbers to counter those of the populous countries with Mediterranean shorelines. There are two Koppen subtypes within this climate, separated by summer temperatures, and the “classic” Mediterranean Csa hot summer type dominates in terms of population as it does land area.
Mediterranean population by countries
Mediterranean population by climate sub-type
We step a gear in terms of population sizes now as we reach number four in our list, the Continental climate. Defined by big temperature ranges between summer and winter and plenty of rain and snow, these regions, which occur only in North America and Asia, are home to almost eight hundred million souls. China is the largest contributor here, with its densely populated north eastern region centred around its capital Beijing lying within the wet summer variants of this climate. Next is Russia, where the majority of that vast country’s population is housed on the rich and fertile plains of Eastern Europe, as Ukraine and Poland demonstrate also in this list. A significant chunk of the USA’s population is within this zone, and almost all of Canada’s. There are six different Koppen types here with the classic “Humid” form of year round precipitation and warm summers dominating population as it does land area. Almost all of the population of the “Monsoon” types are from China, with the remainder from Korea. The dry summer variants demonstrate their rarity in this chart, making up only a tiny fraction of the whole.
Continental population by countries
Continental population by climate sub-type
Onto number three now in our most populated climate zone list, and one of the biggest surprises. Close to one billion people on our planet live in hot desert or hot semi-arid conditions. The Indian Subcontinent dominates here, with the dry region of Western India and Pakistan being inhabited in great numbers in this generally highly populated part of the world. Common with Pakistan and two other countries on the list – Egypt and Iraq – is the presence of major rivers flowing through an otherwise completely barren region – the Nile in Egypt, the Indus in Pakistan and the Tigris/Euphrates in Iraq. These rivers provide for vast areas of irrigation, allowing huge bounties in crops in the ever-present sunshine. Other significant populations occur across the Sahel semi-arid region immediately south of the Sahara desert. In terms of Koppen climate types, the true desert and semi-arid forms are fairly evenly split in terms of population.
Hot Desert population by countries
Hot Desert population by climate sub-type
We’re now down to the final two – the two most populated climates on Earth. It was actually a close call in terms of the numbers. Both have enormous populations. If you’ve watched my other videos you’ll have heard clues about which ones they are, if you’ve not already worked them out now by a process of elimination.
Ok, so the second most highly populated region of earth is… The Tropical Wet and Dry zones – the Tropical Monsoon and Savannah. Spreading out across a vast swathe of the Tropics, and encompassing such well known populous nations as India, Indonesia, Nigeria, Bangladesh and Brazil, it’s no surprise that this climate type is topping out in terms of population. Two… billion… people, ladies and gentleman. That’s over one in four of all people on our planet. The reason for this is simple – the combination of all year round warmth and plenty of rain, albeit in a seasonal pattern, allows for bountiful crop harvests, often multiple times per year, feeding vast numbers. India, with its vast population in its southern half, makes up a full quarter of the total in this climate zone at half a billion alone. In the Koppen classification, the Monsoon and Savannah separate out the Tropical Wet and Dry climates, with the Monsoon being wetter with less distinct dry seasons than the Savannah. As the Savannah accounts for more land area than the Monsoon, it makes up the majority of population also.
Tropical Monsoon & Savannah population by countries
Tropical Monsoon & Savannah population by climate sub-type
And so we come to number one on our list. The climate zone with more people in it than any other. This is the subject of Chapter 5 in my Secrets of World Climate series, when at that time I mentioned its large populations and awarded it with the most number of major world cities than any other. Lying just beyond the tropics, and found on the easterly margins of every continent of earth, it is home to a whopping 2.2 billion people. It is defined by hot and wet summers, but comparatively cool winters… And unless you follow climate, you’ve probably never heard of it. It is the Humid Subtropical.
Humid Subtropical population by countries
Humid Subtropical population by climate sub-type
The vast population of China – almost two thirds of that country’s population are in this zone – a billion people! The equally vast population of India – a third of Indians live in this zone – half a billion again. And what about the United States? Over half of all Americans live in this zone – that was a surprise even to me. Almost ninety percent of Japanese live here in their overcrowded islands. It is probably the most culturally and geographically diverse of any climate zone.
Global Population by Climate Type
Something about this climate type allows it to support such vast populations. With plenty of rain, either throughout the year, or during the summer, there is plenty of water. But unlike the tropics, the winters are cool – perhaps this is the clue – in that tropical diseases are much less common here, allowing for healthier populations. It is unclear. But the population densities are higher here than in any other zone, on practically every continent.
The two subtypes are broken down by rainfall pattern, Cfa for year round rain, and Cwa for a summer monsoon peak. Interestingly they both contribute near equally to the huge population numbers at a billion each.
So, with our list complete, let’s now make a comparison of our twelve grouped zones, in our final graphic. This chart shows just how dominant the two largest climate types are, with over half the people in our planet living in them. The next quarter of our planet’s population live in the next two, while all other climate types fill out the remaining quarter. In some cases these differences in population score are a reflection of the relative land areas taken up by such zones – for instance Mediterranean zones occupy a much smaller land area than, say the Tropical Savannah. But in other cases, such as the subarctic, it can be seen that such vast areas support comparatively little population. This demonstrates that the most populous regions of earth are indeed a result of climates that offer plenty of clean, running water. It’s not really any more complex than that.