Factors which influence climate on a global scale Higher Geography Atmosphere

Introduction The Earth receives heat energy (radiation) from the Sun. But not all of the radiation that arrives at the edge of the atmosphere gets to the Earths surface. Also, not all latitudes on the surface receive the same amount of radiation (sunlight).

The global heat budget The global heat budget is an atmospheric system which involves inputs, storage and outputs. Generally speaking, incoming solar radiation is balanced by outgoing terrestrial (Earth based) radiation. The balance between incoming and outgoing radiation is known as the global heat budget.

Inputs The earth receives all of its incoming radiation from the sun (solar energy). 100%

Atmosphere 23% absorbed by atmosphere 46% absorbed by the surface The global heat budget

Earths Albedo The earths albedo is the reflectiveness of the surface. In our diagram this was responsible for 31% of the radiation loss. Radiation reflected by clouds (17%) + radiation reflected by atmospheric gases and dust (8%) + radiation reflected by the surface (6%) = 31% (total albedo).

Outputs Balancing the input is an equal output of heat (terrestrial radiation) from the Earth. 6% of this energy is radiated back into space. The remaining 94% is absorbed by water vapour and carbon dioxide in the atmosphere and re-radiated. Carbon dioxide and water vapour are both examples of greenhouse gases

The greenhouse effect Eventually all radiation returns to space but the atmosphere’s greenhouse effect slows things down. The greenhouse effect acts like a huge blanket, limiting the heat energy lost. Without the greenhouse effect the global temperature would be 33°C lower.

Energy Receipt with Latitude Factors which influence climate on a global scale

Insolation Insolation is the suns (solar) radiation which is received by the Earth’s surface.

Tropical latitudes receive more solar radiation than the polar latitudes for 3 main reasons. In Polar regions the radiation has to penetrate a greater depth of atmosphere (absorbs more heat). The same amount of solar energy is received over a much greater area in Polar regions (less heating). High energy loss at poles because of ice cap albedo. Equator (0º) North Pole South Pole

Albedo Effect The amount of energy actually absorbed by the surface depends on the Albedo effect. This is the proportion of radiation which is reflected by different surfaces.

Albedo of various surfaces

What does this mean? 90ºN 60ºN 30ºN Equator 0º 30ºS 60ºS 90ºS 0 100 200 300 Insolation (Joules) Latitude 35ºN 35ºS Terrestrial Radiation Insolation

In theory! Theoretically, an imbalance in energy receipt should result in the Tropics becoming hotter and the Poles becoming even colder.

90ºN 60ºN 30ºN Equator 0º 30ºS 60ºS 90ºS 0 100 200 300 Insolation (Joules) Latitude 35ºN 35ºS Energy Surplus Energy Deficit Energy Deficit However, energy is transferred from areas of surplus (Tropics) to areas of deficit (Poles) by atmospheric circulation and by ocean currents.