Positive and
Negative Feedbacks
Assume that the Earth is warming.
¥Warming leads to
more evaporation from oceans, which increases
water vapor in atmosphere.
¥More water vapor
increases absorption of IR, which
strengthens the greenhouse effect.
¥This raises
temperatures further, which leads to more evaporation,
more water vapor, warmingÉ
¥ÒRunaway Greenhouse EffectÓ
=>ÕPositiveÕ Feedback Mechanism