Penn State NASA

Global Climate System


Global Climate System

Now, let’s consider the connection between this idea of an energy flow system to the actual Earth. As shown in the figure below, this system includes the atmosphere, the oceans, volcanoes, plants, ice, mountains, and even people — it is intimately connected to the whole planet. We will get to some of these other components of the climate system later, but to begin with, we will focus on just the energy flows — the yellow and red arrows shown below.

Drawing of the global climate system, showing the flows of energy and greenhouse gases that are key components of the system, see caption
Basics of the global climate system showing the flows of energy, water, and CO2 that are important in controlling the climate. Solar energy drives the global climate, but clouds, plants, volcanoes, ice, and the oceans all play important roles in regulating the Earth's greenhouse and determining what happens to the solar energy. CO2 and water are the principal greenhouse gases that absorb heat emitted from the surface and then re-radiate the heat back to the surface; this process maintains the Earth's temperature at a comfortable level.
Credit: Penn State Department of Geosciences, Modeling Earth's Climate System with STELLA

Numbers in the figure refer to the following key:

  1. Incoming short-wavelength solar radiation
  2. Reflected short-wavelength solar radiation
  3. Emission of long-wavelength radiation (heat) from surface
  4. Absorption of heat by greenhouse gases and emission of heat from atmosphere back to surface (the greenhouse effect)
  5. Emission of surface heat not absorbed by atmosphere
  6. Evaporation cools surface, adds water to atmosphere
  7. Condensation of water vapor releases heat to atmosphere, precipitation returns water to surface
  8. Evapotranspiration by plants cools surface
  9. Chemical weathering of rocks consumes atmospheric CO2
  10. Oceans store and transfer thermal energy
  11. Sedimentation of organic material and limestone (CaCO3) transfers carbon to sediment on the ocean floor
  12. Melting and metamorphism of sediments sends carbon back to surface
  13. Emission of CO2 from volcanoes
  14. Emission of CO2 from burning fossil fuels
  15. Cold oceans absorb atmospheric CO2
  16. Warm oceans release CO2 to the atmosphere
  17. Photosynthesis and respiration of plants and soil exchange CO2 between atmosphere and biosphere

The figure above includes some new words and concepts, including short-wavelength and long-wavelength radiation, that will make sense if we devote a bit of time to a review of some topics related to energy.