Feedback loops

Feedback Loop (Climate)

Processes that can either amplify or diminish the effects of climate forcings; can be positive or negative.

Positive Feedback Loop

A process whose impact amplifies its own effect, increasing its impact in future cycles.

Negative Feedback Loop

A process whose impact lessens its effect in subsequent cycles, creating stability.

Carbon Sink

Absorbs more carbon than it releases; removes CO₂ from the atmosphere.

Carbon Source

Releases more carbon than it absorbs; adds CO₂ to the atmosphere.

Effect of Excess Carbon Sources

If carbon input from sources exceeds removal by sinks, atmospheric CO₂ increases and the planet warms.

Major Greenhouse Gases

Carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), chlorofluorocarbons (CFCs), and water vapor (H₂O).

Purpose of Greenhouse Gases

Keep Earth warm enough for life, but too many cause excessive warming.

Five Factors Affecting Atmospheric Temperature

Changes in solar energy

atmospheric albedo

surface albedo

surface absorption

greenhouse gas concentration

Melting Polar Ice Caps Feedback

Ice melts → less sunlight reflected → more energy absorbed → atmosphere warms → more ice melts.

Melting Permafrost Feedback

Permafrost melts → methane released → methane traps heat → atmosphere warms → more permafrost melts.

Increased Natural Fires Feedback

More fires → more CO₂ emitted → CO₂ traps heat → atmosphere warms → drought and more fires

Increased Cloud Cover Feedback

Atmosphere warms → evaporation increases → more clouds → more sunlight reflected → Earth cools slightly.

Erosion and Weathering (Aerosols) Feedback

Atmosphere warms → more precipitation → more weathering → more aerosols → more reflection → Earth cools slightly.

Silicate Weathering Feedback

Atmosphere warms → precipitation increases → CO₂ in rain reacts with rocks → less CO₂ in atmosphere → Earth cools slightly.

Snowball Earth

Periods in Earth’s history when ice covered most of the planet, potentially caused by runaway feedback loops.

Snowball Earth Cooling Phase

Massive volcanic activity → more exposed silicate rocks → increased weathering removes CO₂ → cooling → ice expands → less sunlight absorbed.

Snowball Earth Warming Phase

Massive volcanic activity → increased CO₂ in atmosphere → warming → ice melts → more sunlight absorbed → further warming.