Tomas Pueyo Profile picture
Apr 1 21 tweets 8 min read Read on X
This video of the Rock of Gibraltar gives an intuition for why some areas of the world have deserts next to rainforests

What's happening here?
How can you use that to predict where there will be deserts or rainforests?🧵
Look at the map below: In some places, deserts and lush forests are side by side. Why?

The mountain chains between them Image
The effect is called the Rain Shadow:
• Air comes wet from the sea
• As it hits mountains, it goes up
• Higher altitudes are cooler, so the air cools
• That condenses water (like the droplets on you Coke glass)
• Rain falls
• Air is dry past the mountains Image
That's what's happening in Gibraltar: You can see the water condense as the air lifts up

If the mountains are tall enough, they can completely stop the water
With this, you can predict where there are a bunch of rainforests and deserts in the world:
1. In what direction do winds blow?
2. Where are there tall mountain ranges?

The 1st question is mainly determined by the rotation of the Earth: Image
This is why around tropical areas, east coasts tend to be wet while everything west of a high mountain range tends to be dry:

Brazil and northern Argentina are wet, but past the Andes it's drier—like the Atacama Desert

Eastern Australia is wet, western Australia is drier.
Image
Image
This effect is inverted if you go further north or south
This inversion is most striking around the Andes Image
But the rotation of the Earth is not the only driver of winds. Monsoons are driven by big masses of land dragging in moist air from warm oceans. This is true in Africa, where monsoons come to central Africa from the west and southern Africa from the east
This creates 2 African deserts:

The Nile—which gives life to ~200M ppl—forms in the Ethiopian Highlands, which take all water from monsoon winds, leaving Somalia as a desert

The reverse is true southwards: eastern South Africa and Mozambique are wet, while Namibia is dry Image
The same is true in Asia. This is why India is so much wetter than Tibet. This is a side view of the Himalayas and Tibet.

Left: India (south)
Right: Tibet (north) Image
The same happens in in Northern Spain and Northwestern Africa: Prevalent winds come from the Atlantic, and both areas have mountains, catching the wind's moisture and creating vegetation

Past the mountains, it's dry or even desertic Image
Look at these 2 pictures. They're taken 5km away, before and after a tunnel in northern Spain
Image
Image
Similar effects can be seen in other areas of the world, where mountain ranges split deserts from rainforests. Here, in the Middle East, you have 3 such areas Image
This is how you get amazing pictures like those of Tehran, the capital of Iran, which is at the edge of a desert but towered by snowy mountains

If you thought Iran was just desert, I present you the Hyrcanian Rainforest

Image
Image
Image
This is also true in Saudi Arabia and Yemen. Why do you think people live mostly on the west and eastern borders (where Mecca and Medina are)? They get the little water carried by the wind from the Red Sea

Left: Arabian Peninsula
Right: Population density
Image
Image
This topographic map shows the mountains that cause all these rain shadows in Spain, northwestern Africa, Turkey, Iran, the Levant, and Saudi Arabia Image
So that's the rain shadow effect

I'm soon going to cover a very related (and hot) topic: Why are warmer countries poorer?
Follow me to see it, or better yet, subscribe to my free newsletter
unchartedterritories.tomaspueyo.com/subscribe
Sorry I meant west and southern borders
Somebody has mentioned the Foehn Wind, which is the dry wind that blows past the mountains. In the Bay Area it's part of @KarlTheFog
In the rest of the world, I think we call it rolling fog
What are other examples where this happens? Share pictures and maps!
Original Gibraltar video from @MetOGibraltar !

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More from @tomaspueyo

Apr 3
This machine makes fuel from thin air
It's carbon neutral
And it does this at record-low costs
Energy and the environment will look completely different in 10 years
Here's why: 🧵 Image
The problem with fossil fuels today is not that we burn them, it's where they come from: They had been locked in the ground for millions of years and now they're back in the atmosphere. The pbm is the "fossil", not the "fuels"

If we make fuels out of thin air, we can burn them Image
How can we do it?

Natural gas is mostly methane (CH4)
You just need some energy to force some carbon (C) to bing to hydrogen (H)

Carbon can come from air (CO2)
Hydrogen can come from water (H2O)
The energy can come from the sun (solar panels)

That's what @TerraformIndies does Image
Read 11 tweets
Mar 8
Egyptian pyramids are not where they're supposed to be. Why?
Why is Cairo, the biggest African city, where it is today?
Alexandria?
Why do over 100M Egyptians live so densely clustered?
These questions all have the same answer. Look:
1st map: population density
2nd map: satellite
The "flower" is the inhabited part of Egypt, which is basically the NileImage
Image
It makes sense: outside of the Nile, Egypt is like the rest of the Sahara desert, an inhospitable hell for humans Image
Read 24 tweets
Mar 4
Global warming is accelerating
There's only one thing we can do today to delay it before we burn, enough to solve the pbm: SO2 injection

Some ppl are squeamish about it but they shouldn't be. SO2 is so obviously the right solution that we should do it now. Here's why:
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There is no way we can stop carbon emissions on time

The Earth is reaching 1.5ºC of warming, but carbon emissions are higher than ever, carried by emerging economies that won't stay poor just for the environment
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Solar, wind, nuclear, batteries, electric vehicles... All of these will curb CO2 emissions soon, but not soon enough. They will take decades

And extracting CO2 from the atmosphere is very expensive: ~$100 per ton Image
Read 23 tweets
Feb 23
This is the ghost of Poland's past
Poles call this type of map "widać zabory": "You can see the partitions"
What partitions?
Why is Poland like that today?
What does it tell us about the country?
About Russia? Germany?
Let's explore:
You might have seen this map already: It overlaps Poland's election results with the old German empire borders

So is that region different because of German influence and investment? That's only a tiny part of the story. This can be quite misleading! Image
Consider these other maps: They highlight not one internal border, but three—between the German, Russian, and Austro-Hungarian parts

Why does Poland have areas from three regions?
Read 26 tweets
Feb 19
Germany just became the 3rd largest economy
But why is it so rich?
Work ethic?
Here's a huge factor: Geography 🧵
If there was something special about 🇩🇪, we should be able to tell it in the regional GDP numbers: It should stand out. But no: regions of neighboring Netherlands, Belgium, Luxembourg, England, and Northern Italy are as rich or richer Image
Why are Denmark and the Netherlands richer than Germany in terms of GDP per capita if Germany is so well run? Image
Read 24 tweets
Feb 16
Why is Berlin the capital of Germany? It's much less straightforward than you might expect!

The story involves kings, emperors, imperial roads, rivers, seas, plains, trade, and a crucial 200 m hill

Here it is: thread
First, Berlin is not central. Most capitals try to be, but Berlin is in the northeastern corner of the country Image
Also, most European capitals are on the biggest regional river:
London➡️Thames
Paris➡️Seine
Rome➡️Tiber
Vienna/Budapest/Belgrade➡️Danube
Warsaw➡️Vistula
Kiev➡️Dnieper

Not Berlin! Image
Read 20 tweets

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