19 April 2016

Back to Milankovitch

My favourite timescale is the Milankovitch timescale. My PhD was about things happening on that timescale; it's the timescale of tens to hundreds of thousands of years. A lot has been happening at that timescale! But not everybody might be familiar with who Milankovitch was and why he has this order of magnitude of time named after him.

Milutin Milankovitch (Милутин Миланковић) was a Serbian scholar who was the first to properly link the changes in the Earth's orbit (caused by gravitational effects of other celestial bodies) to climate cycles. Back in the days, ice ages came and went at the rhythm of the changes in the tilt of the Earth's orbit (every ~40.000 years). Since some 800.000 years ago, the have been coming and going at the rhythm of changes in the Earth's orbit's shape (every ~100.000 years); it never is entirely circular, and the more ellipsoid it is, the more climate is variable. The rotation axis of the Earth also wobbles, like a spinning top; that has effect too. Milankovitch was the first to calculate the effects of these orbital variations on the Earth's energy budget. Since then said orbital variations are known as Milankovitch cycles.

File:Milutin Milanković.jpg
Milankovitch in his earlier years
The way I summarised it above is a bit concise; there is much more to it of course. And it seems that A-level students in this country, who do geography, need to know all this. The teachers, however, may strugle a bit with explaining it all, so they called for help from universities. Last year they had sent an email out to call for help; Jaco took up the challenge. This year, however, he is otherwise engaged, so someone else had to do it. It ended up being me.

I took the opportunity to both brush up and enhance my knowledge on the topic. In my first year's lectures I get 50 minutes to do climate cycles; this time I can do a whole hour on Milankovitch cycles alone. Jaco smuggled in some more cycles, but I have chopped htese bits out; more time to go into Milankovitch, in detail. It's interesting to do; there's always more to learn! And this is of eternal use to a climate scientist. But it's a lot of work too. I spent the entire Sunday at it, and my day job is also making sacrifices. I am in a way glad they asked me to submit my slides by Thursday; then I can't work on it anymore on Friday, and get other things done!

I hope the audience on Saturday is responsive. I hope it'll be nice! And then on Sunday I will take the day off!

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