Positive & Negative Feedback

Question 1

Define negative feedback mechanisms

Answer 1

When an environmental change causes other changes to decrease rate of initial change

Question 2

Define positive feedback mechanisms

Answer 2

When an environmental change causes other changes to increase rate of initial change

Question 3

Increased low level cloud (—)

Answer 3

• Higher temp increases evaporation

• increases condensation and produces clouds

• Clouds have high albedo and reflect sunlight away
—> warming reduced

Question 4

Increased photosynthesis (—)

Answer 4

• higher temp increases rate of photosynthesis

• removed CO2 from atmosphere

• If CO2 stored in woody tissue; CO2 levels will rise and warming is reduced

Question 5

Melting permafrost (+)

Answer 5

• Frozen soils contain methane that is trapped by permafrost

• Warming causes soil to defrost; releasing methane

• Methane is a GG, causing warming

Question 6

Increased Forest/Peat fires (+)

Answer 6

• Peat bogs have waterlogged soil where organic matter builds up

• As they warm up, peat fires more frequent so CO2 is released and less carbon is present in peat

• more fires cause more CO2

Question 7

Release of methane hydrate (+)

Answer 7

• DOM in deep sea sediments has decomposed; producing methane

• High pressure and low temp forms methane hydrate in sediments

• If temps rise it may melt releasing methane gas into atmosphere
—> temps rise further