Changes in the energy balance due to external forces

1. Changes in the energy balance due to external forces

2. What are ‘external forcings’? Processes both outside and within the atmosphere that can force changes in climate What is ‘climate forcing’? Any mechanism that alters the global energy balance and ‘forces’ the climate to change in response.

4. Solar Radiation - Milankovic Total solar radiation reaching the Earth varies due to the Earth’s orbit. This was a theory developed by a man called Milankovic Milancovic argued that the surface temperature of the Earth changes due to variations in the Earth’s orbit and axis tilt.

6. Solar radiation – sunspot activity The amount of solar radiation emitted by the sun varies as a result of sunspots. They are dark spots that appear on the sun caused by intense magnetic storms. Decreases of 0.2% of solar energy occur during the week long passage of large sunspots.

7. Changes in albedo What does ‘albedo’ mean? The Earth’s albedo is the proportion of solar energy reflected from the Earth back into space.

8. Albedo examples

9. Global brightening/dimming Global brightening – an increasing amount of sunlight reaching the Earth’s surface caused by an intensification of solar radiation Global dimming – a worldwide decline of the intensity of the sunlight reaching the Earth’s surface, caused by particulate air pollution and natural events, for example volcanic ash NOTE: Like other areas of this topic…..This is an area of ongoing research and debate.

10. Volcanic Volcanic activity can alter global climate Major eruptions eject ash, sulphur dioxide, water vapourand carbon dioxide into the stratosphere which are then distributed by winds. In 1991 Mt Pinatubo in the Philippines ejected 17 million tonnes. This reduced the amount of sunlight received at the Earth’s surface This led to temporary temperature falls