// lecture 03

Question 1

Specific Humidity

Answer 1

Ratio of Mass of water vapor per
Mass of air:
specific humidity = mass of water vapor/(mass of dry air + mass of water vapor)

Question 2

Relative Humidity

Answer 2

ratio of humidity to saturation humidity:

relative humidity = specific humidity/specific humidity at saturation

Question 3

clouds form for relative humidity at

Answer 3

greater than 1.0

Question 4

Saturation Vapor Pressure

Answer 4

• The pressure of water
  vapor in equilibrium with a flat wet surface depends
  only on temperature.
• That temperature
  dependence is exponential; the partial pressure of water vapor
  depends exponentially on temperature.

Question 5

If the temperature is increasing, then water vapor should be…

Answer 5

increasing! water vapor should increase at 7% per degree C so 0.6 C should give about ~4% water vapor increase which is what we observe!

Question 6

North Hemisphere Snow Cover

Answer 6

snow cover has decreased by 7.5% since 1922.

Question 7

Detection

Answer 7

showing that the climate change is above the natural variability level and requires a forcing

• uses instrumental records, but they are too short really to determine natural variability over long periods of time
• use paleoclimate records
  use models to estimate level of natural variability

Question 8

attribution

Answer 8

assigning a cause to the climate change, once it has been detected - are we doing it?

• try to estimate natural and anthropogenic forcing of climate such as solar, volcanoes, greenhouse gasing from humans, aerosol forcing from humans, and land use change, deforestation.
• stick these into climate model simulations of 20th century
• look to see if simulation with human forcings is different from simulation w natural only forcings

Question 9

Aerosols and the Flat from 1940-1980

Answer 9

The onset of the Human Volcano between 1940 and 1970 or so is though to have cancelled the greehouse gas induced warming for a time, until the aerosol impact plateaued around 1980, after which the greenhouse gases took over

Question 10

Possible problems with D/Atttribution

Answer 10

• forcings, esp aerosols, are uncertain
• feedbacks, esp clouds, are uncertain which affects sensitivity to forcing
• heat storage in ocean is also somewhat uncertain
• natural variability is based on models and paleoclimate data
• strong psychological pressure to have your model match observations (subconscious fitting)

Question 11

Priorities for Climate Research

Answer 11

• better understand cloud feedback and make sure models are doing it right (get sensitivity better known)
• better understand aerosol forcing, both the direct (reflect solar radiation) and indirect (affect cloud properties) effects. but this is only important in the short term, since CO2 will keep increasing and aerosols can’t

Question 12

Sensitivity of climate is uncertain

Answer 12

which gives a wide range of 2 C to 4.5 C for equilibrium response to 2x CO2

Question 13

Important record: CO2

Answer 13

• CO2 is rising rapidly due to human activity is equally important as the temp. rise in the whole picture of global warming
• monitored accurately at Mauna Loa Observatory Hawaii since 1958

Question 14

Mauna Loa CO2 Record

Answer 14

• first reading in 1958: 316 ppm, most recent in 2012 shows 394.5 ppm (25% increase)
• why here? high mountains are away from near surface variation and hawaii gets clean ocean air most of the time

Question 15

CO2 at other sites

Answer 15

• other sites agree with Mauna Loa, but with different seasonality (due to the growth of vegtation during summer and decay during winter).
• May has the highest CO2 concentration in the NH

Question 16

Evidence of anthropogenic rise

Answer 16

comparisons with industrial fossil fuel usage and deforestation rates show emissions are larger than atmospheric increase (55% of emissions goes into oceans or terrestrial biosphere, 45% into atmosphere)

Question 17

Ralph Keeling’s work

Answer 17

concentrations of oxygen also has been decreasing. oxygen is used up when fossils fuels/forests are burned. if exchange with the ocean was the culprit, oxygen levels would stay the same.

Question 18

Anthropogenic emissions have different isotope concentrations

Answer 18

• isotope: have different number of neutrons in the atom, so different weight
• carbon isotops: caron-12, 13, and 14
• plants use more carbon-12 than carbon-13 as compared with the atmosphere
• carbon-13 fraction has been decreasing (indicating burning of former plant/animal material is the culprit)

Question 19

Other records

Answer 19

consistency of other records gives added confidence that significant global warming is occurring…

• glaciers melting
• sea ice disappearing
• rising sea levels
• water vapor increasing
• oceans warming