Greek philosopher Aristotle may have written the first treatise on Meteorology, around 350BC. He postulated the existence of five geographical zones: **Frigid** (one North, one South) by the poles, **Torrid** (North and South of the Equator) and **Temperate** (one North, one South) in-between the relative Frigid and Torrid zones.

Remarkably, that subdivision still holds. One of Aristotle’s ideas has not survived the test of time though: contrary to his thoughts, **the Torrid Zone is not devoid of life** and especially of human life due to excessive warmth.

And so we can say that **Aristotle was totally wrong. Or was he?**

Let’s perform some quick computations using modern readings and the world as known by ancient Greeks.

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Consider Alexandria and Aswan, in Egypt, the cities used by Eratosthenes of Cyrene to measure the accurately measure the size of the Earth (around a century after Aristotle’s time).

From the BBC Weather website, temperature statistics for both cities can be computed

**Alexandria** (31 degrees North)**:
Average monthly Min: 17.3C
Average monthly Max: 24.9C
Average yearly: 21.1C**

**Aswan** (24 deg N)**:
Average monthly Min: 19.1C
Average monthly Max: 34.25C
Average yearly: 26.7C**

Now, since we know there are 7 degrees of latitude between the two cities, we can compute at what rates temperatures increase going south from Alexandria to Aswan:

**Temperature increase by degree of Latitude:
Average monthly Min: 0.26C/deg
Average monthly Max: 1.33C/deg
Average yearly: 0.798C/deg**

What is the expected temperature at the Equator (Latitude: zero, thus 24 degrees south of Aswan), assuming those rates don’t vary (i.e. temperature trends can be modelled in linearly)?

**Equator **(zero deg)**:
Expected Average monthly Min: 25.5C
Expected Average monthly Max: 66.3C
Expected Average yearly: 45.85C**

Look at those temperatures…**if those were true, truly the Equator would be more or less uninhabitable**.

Therefore: **Aristotle’s idea of a “Torrid Zone” was** not a philosophical fantasy, but **a reasonably estimation compatible** with what was known during ancient times.

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Of course we know the actual values are different. For example:

**Kinshasa** (4 deg N)**:
Average monthly Min: 20.7C
Average monthly Max: 30.4C
Average yearly: 25.5C**

That makes Aristotle’s Climate Model wrong of an amount between 5C and 36C.

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So what are the lessons to take home?

(1) **Climate models** that appear **perfectly reasonable today** can be shown to be **very, very wrong tomorrow**

(2) **Extending a trend means** just **making an estimation** that can be way off reality, especially if the trend is presumed linear

(3) **Temperature is NOT everything**. Actual climate depends on a lot of other things.

At the Equator, like everywhere else on the planet.