December 12, 2012

Advent Atmosphere: Hadley Cells

As the ocean has currents, so does the air. But where the ocean has to move around the continents, air can move over them. The land isn’t flat, but in most places it’s a pretty good approximation of it. Air currents are primarily shaped not...

December 11, 2012

Advent Atmosphere: Ocean Currents

The ocean currents are a single vast system, spanning the globe. Water rises in the north Pacific and flows, a few hundred metres below the surface, past the northern coast of Australia to join the water rising in the Indian Ocean. The combined current flows...

December 10, 2012

Advent Atmosphere: Great Lakes

The cold snap in Europe 12,000 years ago was caused by things warming up in North America. Europe is warmed by an ocean current called the North Atlantic Drift, which is the Gulf Stream to you and me. For fairly complicated reasons, if there’s too...

December 9, 2012

Advent Atmosphere: Younger Dryas

The Younger Dryas event is named after the kind of pollen used as a proxy for the temperature. Dryas octopetala grows at the edge of icy regions. So if you find its pollen at a particular time in a particular place, you know that’s where...

December 8, 2012

Advent Atmosphere: Ice Cores and Ice Ages

There are places in Antarctica where the ice hasn’t melted for fifteen million years. We can’t drill that far down. Our longest ice cores go back about 740,000 years. Long enough to encompass the whole of human history. Long enough to show eight ice ages....

December 7, 2012

Advent Atmosphere: Layer Cake

How exactly do we know what was going on in the atmosphere millions and millions of years ago? If we want to know what the temperature is today, we just stick a thermometer out the window and find out. It is rather more difficult to...

December 6, 2012

Advent Atmosphere: Algae

In the primordial soup era, when life first got started on Earth, it was anaerobic life. It worked without needing oxygen. It had to, because there wasn’t any oxygen around. At this point, the Earth still had a reducing atmosphere. Right now, we have an...

December 5, 2012

Advent Atmosphere: Carbonic Acid

Earth’s oceans did more for us than just sit there being wet. We started off the right temperature to have oceans in the first place, reaching enough pressure to make it rain before the planet was too hot for liquid water. And the oceans have...

December 4, 2012

Advent Atmosphere: Volcanoes and Snowballs

So. A problem. How did Earth get its water? We know it didn’t come from the primordial gas cloud, because it was too hot for that when the Earth was condensing out as a big ball of rock. So the water on our surface and...

December 3, 2012

Advent Atmosphere: Venus, Earth, Mars

After a few million years, when the solar system had cooled down a bit, it became cool enough that gases like water and carbon dioxide could be captured by the rocky inner planets instead of just flying back off into space. Again, if you just...

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