Earth's Energy Budget (Week 3) - Post 2

Earth's Energy Budget - Post 2

          

          Energy is the driving factor of life in the climate system. To understand environmental energy there are three main factors to consider: incoming energy from the sun, reflection of solar energy by earth's land and atmosphere, and the greenhouse effect. Earth's energy budget includes a variety of energy flow feedback systems that determine the equilibrium at which Earth's temperature and conditions rest. In order to understand the energy flow between Earth and the Sun, it is important to first understand the types of energy radiation that occurs. All energy is classified on the electromagnetic (EM) spectrum. The electromagnetic spectrum is the range of frequencies of electromagnetic radiation and their respective wavelengths and energies. Each radiation type has a different wavelength, frequency, and photon energy (energy). Wavelength and frequency are inversely proportional; a radio wave has a lower frequency but a longer wavelength, while gamma rays have high frequency, but a very small wavelength. Frequency and photon energy are directly proportional; radio waves have a low frequency so they are low energy, while gamma rays have a high frequency so a much higher energy level. Now when considering climate science, scientists look at energy levels from the Earth and Sun. The sun is very, very hot, so it has a lot of energy. The large amount of energy means the radiation the sun gives off has a shorter wavelength, particularly a wavelength that is in the visible light range on the EM spectrum. The Earth is much cooler so it gives off radiation that is at the infrared wavelength, a much longer wavelength then the sun. Now the energy that the Earth receives is almost, if not entirely from the shortwave (hot) radiation the sun gives off. To be able to determine whether or not the climate is warming, scientists must look at the inflows and outflows of energy on Earth. About thirty percent of incoming solar radiation is reflected directly back to space. This reflected energy is the driving force for many energy feedback systems that contribute to global climate change. Albedo is the measure of how reflective a surface is; the more reflective a surface is the higher the albedo. for instance, shiny white ice sheets have a much higher albedo then dark green forests. Changes in Earth's surface and atmosphere towards more reflective materials promotes cooling, while changes toward less reflective materials promote warming. Things like melting ice sheets cause less reflectivity, which causes less solar energy to be reflected to space, so an overall warmer climate. Another important example is aerosols and clouds; changes in cloud cover and stock of reflective aerosols in the atmosphere can change Earth's overall reflectivity, and subsequently it's climate. The remaining energy that is not reflected by the Earth is absorbed by it. As Earth absorbs solar energy it then heats up to a temperature at which it can radiate enough energy to match inflow. A small percentage of that energy goes directly to space, however the rest is absorbed and re-emitted by greenhouse gasses in the Earth's atmosphere. A greenhouse gas is one that absorbs and re-emits the specific wavelength of radiation, infrared radiation, coming from Earth's surface. Earth's atmosphere is made up mostly of nitrogen and oxygen, neither of which are greenhouse gasses, however natural and man-made aerosols like carbon dioxide and water vapor have the correct chemical makeup to exist as greenhouse gasses. These greenhouse gases block the reflected solar energy, and emitted energy from earth, from going back to space. By trapping the energy in the atmosphere the energy disperses within the environment and simultaneously warms the climate. With the current increase of greenhouse gases in the atmosphere, the planet is out of balance; inflow of solar energy is higher than outflow of energy. The global climate is warming. 

          The Earth's climate system is made up of thousands of complex factors and moving parts, however there is none more important then energy flow. Energy flow between the Earth and the Sun must be considered in order to understand how increased human carbon emissions cause global climate change. By looking at solar radiation, greenhouse gases, and Earth's energy emissions and reflectivity, it is possible to identify exactly what factors and systems drive the rising temperature equilibrium within Earth's climate.