// lecture 09

Question 1

climate sensitivity: global warming theory

Answer 1

deltaT (change in temp C) = lambda (climate sensitivity in C per W/m2) * deltaF (radiative forcing in W/m2)

Question 2

pos. feedbacks

Answer 2

means a very sensitive climates, a large lambda. a large change in temperature for even a small forcing

Question 3

neg. feedbacks

Answer 3

means a small lambda

Question 4

water vapor feedback

Answer 4

almost certain it doubles the sensitivity of climate, number one GHG, and confident to be positive because warm air can hold more moisture

• almost no argument that water vapor should act as a neg. feedback and observations show evidence for a strong pos. feedback as vapor increases/decreases right along with global temps

Question 5

water vapor content

Answer 5

winters are much drier than summers simply because cold temps means small water vapor content

Question 6

A warmer climate means a higher

Answer 6

water vapor climate. 20% more humid climate with a 3 C increase.

Question 7

water vapor doesn’t care what the forcing is that caused the warming (or cooling)

Answer 7

it’s a feedback; any kind of warming will result in an increase in water vapor content and more GH effect and any kind of cooling will result in a decrease in water vapor content and less GH effect

Question 8

Pressure vs Height

Answer 8

• most of the mass of air is near the surface

- water vapor is confined even closer to the surface because the temp. decreases with height

Question 9

relative humidity

Answer 9

• moist near surface
• dry in subtropics (15-40 N and S)
• very dry in stratosphere

Question 10

warmer leads to…

Answer 10

more water vapor, then a stronger GH effect and then additional warming

Question 11

structure of the atmosphere

Answer 11

• thermospher eis hot because energetic photons (e.g. extreme ultraviolet) is absorbed by N2 and O2, usually by being blasted apart
• stratosphere is hot because ozone absorbs solar radiation
• surface is hot because solar radiation is mostly absorbed there

Question 12

lapse rate feedback

Answer 12

• in the troposphere, the temp. decreases with altitude.
• as air warms, moisture also increases to maintain similar emission temp
• water vapor feedback makes this irrelevant for constant relative humidity. so the fact that the lapse rate might decrease in a warmed world does not cause a neg. feedback

Question 13

ice albedo feedback

Answer 13

warming causes ice to melt which causes the dark open ocean to be visible and leads to more warming; similar for snow

• not nearly as strong as water vapor feedback in global importance

Question 14

clouds

Answer 14

suspended liquid droplets or ice crystals in the air; don’t confuse with water vapor (gas)

Question 15

cloud feedback

Answer 15

much more uncertain than water vapor or ice feedbacks; partially because they have an albedo effect (reflect SW radiation) and a greenhouse effect (emit LW radiation back)

Question 16

feedbacks and climate sensitivity

Answer 16

• climate models say that expected warming is approx. double that expected with no feedbacks.
  1. warming response to double CO2 with NO feedbacks is 1.5 C
  2. models predict 3 C average response to warming with all feedbacks acting

Question 17

uncertainty in feedbacks

Answer 17

since pos. feedbacks combine, high senstivity climates are hard to rule out. very high temp changes (8 C) are unlikely, but hard to rule out but changes like 1 C are essentially impossible.