Chapter 3A Main Ideas

1. Earth as a System

Earth works as an interconnected complex system that can be divided into 5 spheres: hydrosphere, atmosphere, cryosphere, biosphere, and geosphere. Changes in one sphere create changes in the other spheres.

2. Earth’s Energy Budget

The flows of energy into and out of Earth’s system is the Earth’s energy budget. Incoming energy is from the sun, and it is not distributed evenly on the planet. Some solar energy is reflected, and some is absorbed. Absorbed energy works to heat the Earth before it eventually works its way out of Earth’s system again.

3. Climate Forcing Mechanisms

Factors that influence and change climate on the planet can be divided into those that alter the incoming solar radiation, those that change how heat surpluses are moved to heat deficit areas on the planet, and those that effect the reflection and absorption interactions within Earth’s energy budget. Forcing mechanisms work on a variety of timescales and some have larger climate influences than others. The main forcings attributable to humans are alterations to albedo from land use changes, changes to greenhouse gas concentrations and therefore changes to the greenhouse effect, and overall population growth that exacerbates the other two changes.

4. The Carbon Cycle

How carbon moves around on the planet and where it builds up are important controls on climate. Changes to the carbon cycle lead to changes in greenhouse gas concentrations and therefore changes to the energy budget of the planet.

5. Climate Feedback Loops

The Earth system is highly interconnected and therefore a change in one aspect triggers changes in other aspects of the system. Feedback loops are set up by changing climatic conditions that can build on each other creating even more climate changes. Important feedbacks for short-term changes to climate are related to carbon cycling and albedo.