1. ENERGY BUDGET & ENERGY TRANSFERS

2. Quick Review
The world is divided up into 6 major climate zones differentiated according to temperature and precipitation.

3. What makes Earth’s climate what it is?
On Earth, almost all of our heat comes from the Sun.
Without it, earth could be as cold as deep space at -272ºC.

4. Our distance from the Sun matters a lot too.
Pluto:
*40 times farther from the Sun
* Mean daytime temp.: -230ºC
Mercury:
*1/3 the distance from the Sun
* Mean daytime temp.: +350ºC

5. So then the Moon has the same mean temperature as Earth?

6. Unlike the Moon, Earth has an atmosphere
Unlike the Moon, Earth has an atmosphere. So, even though they get the same energy from the Sun, their mean temperatures vary greatly. Moon temperatures Day: +110ºC Night: -150ºC Earth temperatures Day: +24ºC Night: +16ºC

7. The atmosphere has two effects.
1. It keeps the earth cooler during the day by acting like an umbrella.
2. It keeps the earth warmer at night by acting like a blanket.

8. Okay…so how does that work?

9. Closed System
Closed systems allow energy but not matter to cross their boundary. Earth is a closed system. That is, the Sun’s energy can enter and leave the system, but matter stays constant.

10. Energy Transfer
Energy enters Earth’s system as electromagnetic radiation from the Sun.

11. Once in Earth’s system, three main processes transfer energy through Earth’s climate system:
convection
conduction
radiation

12. Conduction
Conduction is the transfer of thermal energy between substances in physical contact.
Thermal energy always moves from the higher temperature to lower temperature.

13. Convection
Convection is the transfer of thermal energy by energized molecules moving from one place to another.

14. Radiation
Radiation is the transfer of energy as electromagnetic radiation. This form of energy can travel through a vacuum of space.
When radiation encounters matter, it can be:
absorbed
reflected
or refracted

16. Energy Budget
The amount of energy entering and leaving Earth’s system must be in balance.
If more energy entered Earth’s system than left, the Earth would continue to get warmer.

17. INCOMING ENERGY
30% of energy radiated from the Sun is reflected back to space by clouds, particles in atmosphere, and Earth’s surface
70% is absorbed by Earth’s surface (heating the water, rocks, and air as well), clouds, and certain gases in the atmosphere

19. OUTGOING ENERGY
When Earth surface absorbs energy, it gains thermal energy and the temperature rises.
The surface emits mostly lower-energy infrared radiation back out.

20. The Greenhouse Effect

21. Land and water gain thermal energy by absorbing the Sun’s short-wave radiation.
The Earth’s surface emits back some of this thermal energy as long-wave infrared radiation, thereby heating the air.

22. The greenhouse effect is a natural process whereby greenhouse gases trap infrared radiation (IR)
Think about a car parked in the sun on a cool day. Why can it get so hot?

23. Can you guess which GHG accounts for 95% of the greenhouse effect?
Greenhouse Gases
Greenhouse gases include:
CO2 –carbon dioxide
CH4 –methane
N2O –nitrous oxide
H2O –water vapour
WATER!
A: Water
Can you guess which GHG accounts for 95% of the greenhouse effect?

24. Back to the beginning…
The world is divided up into 6 major climate zones differentiated according to temperature and precipitation.
But what makes Earth’s climates what they are?
And, why does climate vary so much around the world?

25. LOWER B Latitude Ocean Currents Wind (air currents)
There are a number of factors that impact the temperature and precipitation of a region.
They include:
Latitude
Ocean Currents
Wind (air currents)
Elevation (altitude) Relief (land formations like mountains, valleys)
Bodies of Water

26. LATITUDE Why is it so much warmer near the equator than at the poles?
Because the Earth is shaped like a sphere, the Sun’s radiation strikes the planet at different angles from one latitude to the next.

27. The same amount of light energy comes from the Sun, but that energy is distributed over a larger area as we move away from the equator.
The result is that polar areas are cooler than equatorial areas.

28. Why is our climate hot in summer and cold in winter?
Because the Earth is tilted on an axis of approximately 23.5°, the Northern Hemisphere receives more solar energy during the summer when it is tilted towards the sun.
Use this diagram to guess the climate in southern Argentina in July.
The average high temperature in Patagonia in July is 3°C and the average low is -2°C.

29. So, if Toronto and Nice, France are both at a latitude of 43°N, then they should have the same temperatures, right?
No fair!

30. WIND CURRENTS
Because the Sun’s energy is unevenly distributed, the excess heat from the equator is transferred to the poles.
Wind currents provide one method of heat transfer, bringing thermal energy from warm areas to cooler ones.

31. What makes the wind blow?

32. The heated land and water surfaces can also come into contact with air molecules above them, thereby transferring their energy to the atmosphere.
What do we call this type of energy transfer?

33. When the lowest air warms, it expands and rises leaving room for cooler air to descend and replace it.
This process creates wind.

34. Convection & Energy Transfer
Thermal energy is transferred to other regions of the atmosphere by convection. This energy redistribution happens through wind and ocean currents caused by convection.

35. Convection and Wind
In general, warm air flows from the equator to the poles and cool air flows from the poles to the equator.
The Earth has 3 main wind belts which move heat around the planet: the Hadley, Ferrell, and Polar cells.

36. The Hadley Cell
Warm, moist air rises near the equator and travels along the tropopause. Cool, dry air descends to take its place. This explains the warm, wet climate near the equator and the dry, desert climate near 30ºN and 30ºS.
The Hadley, Ferrell and Polar cells are the 3 main wind belts. Only the Hadley is straightforward enough to explain.

37. Wind patterns
The surface wind in the Hadley Cell is known as the Trade Winds, which blow from east to west. They do so because of the Earth’s rotation. This is called the Coriolis effect.
What do these winds bring to Brazil from the Sahara?
What did they bring to the ‘New World’?
The winds bring nutrients from the desert to the Amazon rainforests.
They brought ‘explorers’ like Christopher Columbus
This link takes you to an animation that helps explain why the Hadley Cell doesn’t move air simply north or south, but rather in a westward direction. This effect is known as the Coriolis Effect.