We all know that as we go higher, it gets colder. Then it stands to reason, any two places with the same altitude will be as cold as each other.
But that isn’t the case! Ooty and Shimla, two famous hill stations in India, are at similar altitudes but experience very different temperatures.
Why would any two places at the same altitude have different temperatures?
In this video, we find out.
Correction: At 2:55, I say that Ooty is 14.1°N of the equator. It is actually 11.4°N of the equator, and the figure in the video is correct.
Transcript of the video
Place your palm horizontally 10 cm over a candle flame.
In 5 seconds or so, your palm will start burning up and you’ll want to move your hand away (please do!)
Now, place your palm over the candle flame at the same height, but tilt it slightly. The center of your palm will feel less hot, and you will probably be able to keep your hand over the flame a little longer.
Tilt it slightly more, and you will barely feel the heat on your palm and you can hold it there as long as you want.
If only I remembered this little experiment in my first climate science class.
In that class, the professor asked us a question.
“Why does it snow in Shimla and not in Ooty, even though they have the same elevation?”
If you are unaware of Indian geography, Shimla and Ooty are both famous hill stations in India. Shimla is a city in North India, at an elevation of 2276 meters above mean sea level. Ooty is in South India, rising to 2240 meters above mean sea level. Despite very similar attitudes, it is much colder in Shimla than in Ooty.
Looking at this from a broader perspective, we are always taught that as we go higher, it gets colder.
Then why would any two locations with the same altitude experience different temperatures?
After enjoying our discomfort for a bit—you know, the way teachers generally do—he finally gave us the answer.
Ooty and Shimla are at different latitudes.
The earth is a curved surface. Because of this curvature, different latitudes receive the Sun’s heat at different angles.
At the equator, the sunlight falls perpendicular to the surface of the earth. Just like in our candle experiment, this high angle means more energy is focused on the surface, making the region much hotter.
As we move to higher latitudes, sunlight falls at lower and lower angles. Again, from our candle experiment, we know that with smaller angles between the surface and the heat source, it feels less hot.
Sunlight also has to travel a longer distance through the atmosphere at higher latitudes, and the atmosphere is really good at dispersing the sunlight and reducing the intensity of the light. This helps in the cooling.
So, let’s look at my professor’s question again. Ooty lies on latitude 11.4°N (I misspoke in the video) and is 1271 km away from the equator. It is within the tropical zone. It receives direct sunlight at a high angle, making it hot.
Well, it doesn’t snow there!
Shimla, on the other hand, lies on latitude 31°N and is more than twice as far from the equator as Ooty: 3460 km. This reduces the angle between the sun’s rays and the surface, making Shimla colder than Ooty.
And that is why it snows in Shimla and not in Ooty.
Now I just need a time machine……
I hope you enjoyed the video and you found it interesting and useful! Have misleadingly simple questions left you stumped? Leave them in the comments!
Thank you for watching Eco-intelligent, as we try to make the world, ecologically intelligent.