The Earth’s Temperature: Factors

The Sun!!!

Incoming Solar Radiation = Insolation Referred to as short-wave radiation Not constant at all latitudes – tilt of the Earth More radiation at the equator, less at the poles

Processes affecting Insolation Scattering – causes insolation to be displaced into many different directions Some lost back to space So the radiation may be scattered

Reflection - possible 100% loss of insolation back to space Interaction with different surfaces or clouds/water vapor

Absorption - Insolation is absorbed, heats up the surface and then causes radiation of its own to be released Long-wave radiation is emitted from the earth’s surface This is also known as infrared radiation

Albedo The percentage of solar radiation reflected back into space Light colours reflect = high albedo Dark colours absorb = low albedo So things that are light coloured (snow) reflect more radiation, while darker things like concrete absorb more radiation

Reflectivity of the Earth’s Surface

Lapse rate and aspect As altitude increases, the temperature drops For every 150m increase in altitude, the temperature drops by 1°C This is known as the lapse rate This is why mountaintops are often covered in snow all year - they don't heat up enough to melt

Aspect refers to the direction something faces In the Northern Hemisphere, hillsides facing South receive more direct energy. Remember, the sun is over the Equator, so if you are in the N Hemisphere the sun is South of you. What about the Southern Hemisphere?

Take a look at figure 17.3 on p.76 of your text Notice how both lapse rate and aspect affect the temperature?

Seasons The earth is tilted on its axis at 23.5° It completes one orbit of the sun every year Because of this axial tilt, different latitudes receive different amounts of radiation over the course of the year

The effect of water Water heats and cools more slowly than land Areas close to water have smaller changes in temperature over the course of the seasons, while areas far from the sea have hotter summers and colder winters Warm ocean currents can also help warm otherwise cold places - eg. Gulf Stream

The Energy Budget Incoming solar radiation (or insolation) is also known as UV or ultraviolet radiation. Insolation heats the planet. The earth emits IR or infrared radiation, which cools the earth. When one of these factors changes it can have great conquest for global temperatures

Greenhouse Gas Effect Gases in the atmosphere, particularly carbon dioxide and methane, are able to trap some long-wave radiation. Reflects this energy back to the Earth, which heats up the Earth even more. This process is necessary to make the earth warm enough to be livable. However, by greatly increasing the amount of greenhouses gasses, we have affected global temperatures.

Without it? Earth would be -18 degrees

Questions 1. Explain how the earth is heated. 2. After watching the video, explain why the Earth has seasons. 3. Explain why the length of days and nights are more even near the equator. 4. In your own words, explain the greenhouse effect.