Earth's Energy Budget
Background: Atmosphere
Earth's Energy Budget
Earth receives a tremendous amount of energy from the Sun. The land, sea, and air absorb some of this energy and reflect some of it back into space. The overall description of this process is called Earth’s energy budget.
One part of this process is what's sometimes called the "heat-trapping blanket." Just as a blanket traps warmth near your body, Earth’s atmosphere traps some of the heat radiated from the Earth. The presence of heat-trapping gases like carbon dioxide keeps the planet’s average temperature at a hospitable 15°C (59°F). (With no blanket effect, Earth’s average temperature would be about -18°C (0°F). Not all components of the atmosphere are heat-trapping gases, however; oxygen and nitrogen, which together make up more than 95% of our atmosphere, are not heat-trapping gases.
The heat-trapping blanket is the major cause of global climate change.
Increases in the atmospheric concentration of carbon dioxide (and other heat-trapping gases) traps more heat and contributes to global warming.
Earth's energy budget. Earth’s surface absorbs shortwave solar radiation (red arrows) and re-radiates longwave infrared radiation (blue arrows). The numbers are percentages: For example, 30% of the solar radiation shining on Earth is reflected away by clouds or the planet's surface.
Aerosols: Particles in the Atmosphere
Aerosols: Particles in the Atmosphere
This satellite image shows a dust plume from the Sahara Desert blowing across the Atlantic Ocean. The orange and red colors represent the highest densities of tiny airborne particles, called aerosols.
Aerosols are another key component of Earth’s atmosphere. These suspended liquid and solid particles include soot from fires and volcanic eruptions, sea salt, bacteria, and viruses. Aerosols affect Earth’s energy budget by scattering and absorbing radiation.
Overall, aerosols likely exert a cooling effect, because many of these particles tend to prevent radiation from reaching the planet’s surface (although due to their size and shape, some aerosols may also help trap heat near the ground).
How Do Scientists Measure Earth's Temperature?
How Do Scientists Measure Earth's Temperature?
Measuring Earth's temperature accurately and consistently requires a process that considers several factors:
- Measurements must be taken in a large and diverse enough range of locations to ensure that their average is truly a measure of global temperature and is not biased toward one region or another.
- Those locations must be chosen so that individual measurements are not thrown off by sources of unusually high or low temperatures, such as cities (which tend to be “heat islands” warmer than the surrounding landscape).
- No measuring device is perfect—all measurements include some amount of error, or “noise.” Understanding the kinds of errors associated with different measurement techniques is a key element in evaluating the accuracy of a given temperature value.
- In addition, the study of climate requires measurements over very long time periods, so sources of paleoclimate data (data on climate from the distant past) are key to putting today's measurements in context.
