Clouds & Particles

Basics

3. Sun and clouds

1. The albedo of the Earth

When sunlight strikes the Earth, how much of it is:

a) reflected?
b) transmitted?
c) absorbed? What happens to the radiation which is absorbed?

2. The Earth's radiation energy per second

The average amount of radiation energy (mainly light) that strikes the Earth every second is:

1.7×10¹⁷ joules

This corresponds to the amount of electrical energy consumed by Norway over 150 days or the amount of electricity consumed over the whole of Europe every week.

How much of this energy from the Sun is reflected? How much is absorbed? Approximately how much infra-red radiation (heat) do you think the Earth radiates back into space each second? Give a reason for your answer.

3. The Earth's night-time blanket 

How do cloudy night-time skies resemble the blanket you put over you when you sleep?

4. Positive and negative feedback effects

One of the effects clouds have on climate is a positive feedback loop:

A hotter climate means more evaporation 
-> more clouds
-> more heat radiation from the Earth is trapped and sent back to the ground by the clouds 
-> a hotter climate 
-> more evaporation 
-> more clouds
- and so on.

Clouds also have an effect on climate which is a negative feedback loop. Describe this!

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About this page:

Authors: Ellen K. Henriksen and Camilla Schreiner - University of Oslo - Norway. Scientific reviewer: Justine Gourdeau - LaMP Clermont ferrand - France - 2004-01-13. Last update: 2004-03-27.