Heat Transport

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From the course by The University of Chicago

Global Warming I: The Science and Modeling of Climate Change

157 ratings

The University of Chicago

Global Warming I: The Science and Modeling of Climate Change

157 ratings

This class describes the science of global warming and the forecast for humans’ impact on Earth’s climate. Intended for an audience without much scientific background but a healthy sense of curiosity, the class brings together insights and perspectives from physics, chemistry, biology, earth and atmospheric sciences, and even some economics—all based on a foundation of simple mathematics (algebra).

From the lesson

Weather and Climate

Another property of the real world, missing in our model so far, is that the real world is not everywhere the same temperature, and the heat fluxes to and from space do not necessarily balance at any given time or location. This is because the winds in the atmosphere and the currents in the ocean carry heat around, in general from the hot tropics up to the cold high latitudes.

Heat Transport3:29

Coriolis Acceleration5:25

Geostrophic Motion5:21

The Turbulent Cascade3:27

Meet the Instructors

David Archer
Professor
Geophysical Sciences

[MUSIC]

So we constructed, at the very beginning of the class,

a very simple model of the climate of the Earth.

And since then we've been improving it and talking about ways in which

it should be more realistic in order to approximate the real world.

And so here we started with just original bare rock model of

energy coming into and out of a planet and that determines the planet's temperature.

Then we added the greenhouse effect with this

plate of glass that absorbs all the infrared light coming from the ground.

And then we talked about how the atmosphere,

the greenhouse gases in the atmosphere don't absorb all of the light.

They absorb only certain parts of the light energy.

And those other frequencies such as the atmospheric window here which

greenhouse gases don't absorb at all.

And then in the last unit we talked about another mechanism of carrying heat around

in the atmosphere in addition to the heat fluxes from light which is convection.

And in particular, we found out that moist convection is what

drives the thermal structure of our atmosphere, so you have here,

rising and it cools and condenses, and that's where it rains.

But it dumps latent heat up here and also carries heat around.

And so that's sort of where we are.

But there's one more thing that the real world has,

that our conceptual models do not have yet.

And that is, that the whole world is not a single place.

It's not all the same temperature and the sunlight intensity is not always in

balance with the energy going out by infrared locally.

[SOUND] So, the real geometry is that you have sunlight

all coming from one direction, from the sun, and

it's coming in most strongly at the equator.

Infrared light is leaving everywhere around the Earth and

the rate at which it leaves depends on the temperature of the ground

according to epsilon sigma T to the fourth.

And it turns out that if you look at a given

location on the Earth, the incoming and outgoing energy budgets do not balance.

They only balance for the Earth as a whole on a long enough time average.

So, here is plot of the sunlight intensity in watts

per square meter as a function of latitude and it's very strong at the equator.

Here is a plot of the infrared energy leaving the earth as a function of

latitude, and it's also stronger near the equator because it is warmer at

the equator than it is at the poles, but there is a deficit.

It's not hot enough at the equator to drive the energy out

as quickly as the sun is bringing it in.

And it's not cold enough at the equator at the high latitudes for

the infrared to be as low as the sunlight coming in.

And the difference is what we call heat transport.

It's heat being carried by the atmosphere and

by the oceans from the low latitudes to the high latitudes.

[MUSIC]

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