Midterm 1 Forcings, Feedbacks, and Sensitivity

Question 1

Forcing –

externally driven _____ to earth’s energy balance (e.g., solar, volcanic, land cover, pollution,
GHGs from fossil fuels)

Answer 1

change

Question 2

2x CO2 forcing = 4 W/m2, and causes ____ warming on its own

Answer 2

1.2 ̊C

Question 3

Feedbacks – affect and affected by climate; positive ____ initial change, negative _____ initial
change

Answer 3

amplify, counteract

Question 4

Fast feedbacks (respond in hours to years):
Snow-albedo, water vapor, clouds

Question 5

Slow feedbacks (respond in decades to millennia):
Vegetation, carbon cycle, ice sheets

Question 6

Climate sensitivity = global average warming due to 2x ___, including effects of fast feedbacks

Answer 6

CO2

Question 7

2x CO2 by itself causes ___ global warming

Answer 7

1.2°C

Question 8

This kicks off feedback loops, which lead to roughly _____ of final warming

Answer 8

2.5 to 4°C

Question 9

Ways we estimate climate sensitivity – past climate changes, computer models, using short-term climate
variations that scale with its long-term sensitivity, quantify feedback loops

Question 10

The more climate
responded to forcings in
the past, the more it will
also respond to rising
CO2 in the future.

The more climate changed in the past, the more it is likely to change in the ___ (i.e., higher sensitivity)

Answer 10

future

Question 11

Earth’s surface takes many centuries to ____ up due to big oceans swallowing heat (e.g., warming
continues for long time even after CO2 level stabilizes)

Answer 11

warm