Clouds & Particles

Basics

3. Sun and clouds

1. Earth's albedo

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. Earth's radiation energy per second

The average amount of radiation energy (mainly light) that strikes the earth in one second is

1.7×10¹⁷ joule

This corresponds to the electric energy consumption of Norway for 150 days or that of Europe for 7 days.

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

3. Earth's night blanket 

How does the Earth's cloud cover during night-time resemble the blanket you put around you when you sleep?

4. Positive and negative
feedback effects

One of the effects clouds have on climate may be called a positive feedback loop:

A hotter climate means more evaporation 
-> more clouds
-> more of the heat radiation coming from the Earth being trapped and sent back by the clouds 
-> a hotter climate 
-> more evaporation 
-> more clouds
- and so on.

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

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.