Energy: The Driver of Climate - Review

You have learned that the balance between incoming energy from the sun and outgoing energy from Earth ultimately determines Earth’s climate. This is actually explained by the first law of thermodynamics (or the law of conservation of energy).

Incoming solar energy from the sun primarily consist of shorter wavelengths of energy, mostly in the visible part of the electromagnetic spectrum. To balance the absorbed incoming energy, Earth must, on average, emit the same amount of radiation back into space. Because Earth is colder than the sun, it emits radiation at much longer wavelengths (in the infrared part of the spectrum). Greenhouse gases in Earth’s atmosphere absorb some of this infrared radiation, which is then re-emitted back toward Earth’s surface to maintain an average global temperature of approximately 15°C (59°F).

The Stefan-Boltzman law explains that if the incoming and outgoing energy are not balanced, a planet either cools or warms. An imbalance in the overall energy budget can result as the concentration of greenhouse gases increases. Greenhouse gases absorb and emit infrared radiation back to Earth. Balance to the energy budget can be restored if Earth’s average global temperature increased.

Human civilization has advanced and spread across the planet throughout a very brief period of recent geologic history. During this time, Earth’s average global temperature has changed very little. In the next module, you will investigate whether the recent warming trends is unusual. You will also compare trends for Earth’s temperature over different lengths of time, from decades to over 100’s of thousands of years. You will also analyze temperature trends for different geographic regions.

Now that you have completed this module, you may return to the home menu to begin the next module, Temperature Over Time.