How Ice Ages Work
This week two studies looked at old ice: one suggests part of Tibet's Guliya ice cap is more than 128,000 years old, another offers an ocean model for why carbon dioxide fell in past ice ages. This film explains the fundamentals behind them: how Louis Agassiz read the idea of an ice age in boulders, what the world looked like 21,000 years ago when the Gulf of Thailand was dry land, how three slow changes in Earth's orbit and tilt change summer sunshine in the north, how Milutin Milanković calculated them, how ocean mud proved him right in 1976, how ice and carbon dioxide amplify a small nudge, what is still unexplained, and why today's warming is not orbital.
The wobbling orbit that paces Earth’s ice
How ice ages come and go.
The idea of an ice age
Boulders in the wrong place.
The last great freeze
Ice kilometres thick, and a lower sea.
A wobbling orbit
A janitor looks to the sky.
Milanković’s sums
Sunlight, calculated by hand.
Proof in the mud
Tiny shells keep the score.
Amplifiers
A small push, made loud.
A small push, a changed planet
What the ice ages say about today.
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