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Variable scenarios GLOBAL WARMING Temperatures are rising General principles, not numbers. GLOBAL WARMING “Greenhouse Effect” Solar Energy Balance (complicated mass balance problem) Three notable points about this graph 1 2 3 How does one ‘read’ past temperatures from ice?

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Presentation Transcript
slide1

Variable

scenarios

GLOBAL WARMING

global warming greenhouse effect

General principles, not numbers.

GLOBAL WARMING “Greenhouse Effect”

Solar Energy Balance (complicated mass balance problem)

three notable points about this graph 1 2 3
Three notable points about this graph123

How does one ‘read’ past temperatures from ice?

slide10
Given that people were not measuring temperature or atmospheric CO2 400,000 years ago, how can we construct the previous graphic?

Isotope formation (C, N,..) is temperature dependent.

Isotopes are in equilibrium in atmosphere.

Deposition captures a signal of the isotope ratio of the atmosphere

This isotope ratio can be calibrated to detect a climate signal.

Deposition can come from ice cores (H2O, CO2), diatoms (calcium carbonate), or other hard sediments.

O18/ O16

C13/ C12

slide12
The temperature of the earth is a matter of heat balance between solar inputs and loss through the atmosphere
  • The earth’s temperature is determined by:
    • The amount of solar energy the earth receives
      • Sunspot activity causes fluctuations
      • Variations in earth’s orbit around sun
    • The amount of solar energy the earth reflects / refracts
      • A function of the planet surface and atmosphere
    • Retention of heat by the atmosphere
      • A function of natural and anthropogenic gases
    • Evaporation and condensation of water vapor
      • Climate provides feedback to modify itself
slide13

Climate varies because solar energy varies

Milankovitch

cycles

Variation in the Earth’s orbit causes variation in solar energy absorbed and drive long term climate change

slide14

SURFACE TEMPERATURE

Al Gore “AIT” point: --The 10 warmest years on record have ALL been in the last 14 years.---

Temperature deviation

The trouble with temp:

1900 1920 1940 1960 1980 2000

Recently, temps are up, up, up

where we now stand
Where we now stand

30%

370 ppm

285 ppm

slide19

Gases vary in heat trapping abilities. Larger molecules trap more heat. Larger molecules also remain in atmosphere longer.

slide20

Other greenhouse gases are increasing as well

  • SOURCE:
  • Livestock
  • Draining wetlands
  • Warming wetlands
  • Industry

985 1185 1385 1585 1785 1985

what we know for certain
What we know for certain
  • The concentration of heat trapping gases in the atmosphere is rising
  • The earth’s temperature is rising
  • The scale of both is consistent with human caused global warming
global circulation models gcm s
Global Circulation ModelsGCM’s
  • Models
    • Hadley Cell models --UK
    • CCC- Canadian Climate Centre models
    • PCM (US DOE / NCAR) , others
  • Idea:
    • Model climate on 1o grid cells, as we understand it.
    • Verify by predicting modern climate
    • Modify atmosphere (add greenhouse gases, stir)
    • Predict future
slide29

2

2

1

2

3

2

3

  • Ice clouds reflect more solar energy than water clouds
  • Particulates reflect heat rather than trap heat
  • High surface albedo reflects heat rather than absorb it
add surface effects that drive climate from solar energy
Add surface effects that drive climate from solar energy
  • Evaporation
  • Latent heat
  • Condensation
  • Convection currents
  • Air pressure differences
  • Coriolis effect

Climate: a collection of the earth’s weather

and you get a model
And, you get a model…

December, January February June, July, August

GFHI GFHI

UKHI UKHI

Predicted Temperature Increase: greatest at high latitudes during the winter months

slide33

2001

Report

slide35

HADLEY MODEL

PCM MODEL

WINTER

Summer

Reduced BAU

Reduced BAU

slide36

Fig. 2. Average snowpack SWE for 2020-2049 and 2070-2099 expressed as a percent of the average for the reference period 1961-1990 for the Sierra Nevada region draining into the Sacramento-San Joaquin river system

Hayhoe, Katharine et al. (2004) Proc. Natl. Acad. Sci. USA 101, 12422-12427

Copyright ©2004 by the National Academy of Sciences

model uncertainty is large
Model uncertainty is ‘large’

3.5-8.5oC at equilibrium

Think about this as a probability distribution with 3.5 and 8.5 equally likely, but 5.5 much more likely than either.

uncertainties
Uncertainties
  • Cause and Effect.
    • We have a model, but we do not have the ability to conduct a controlled experiment with the atmosphere.
  • Spatial variability in warming varies among models
    • It is very variable; predicting this variation is problematic
  • Consequences of warming
    • eg, sea level rise; health issues; agriculture, natural habitats
primary sources of uncertainty
Primary sources of uncertainty
  • Aerosols in the atmosphere
    • Large fire events (eg, Indonesia, Mexico)
    • Volcanoes (eg, Mt. Pinatubo)
    • Air pollution
  • Feedbacks from natural systems
    • Clouds and water vapor
    • Ocean currents
    • Surface albedo, outgassing of marshes, etc
  • Human behavior with respect to emissions
uncertainty hmm
Uncertainty, hmm?
  • Use a consensus-based approach.
  • Use UN as a platform to convene large groups of scientists to discuss and agree upon statements regarding:
    • Likely magnitude of greenhouse gas emissions under various future scenarios
    • Likely effects of those emissions on climate
    • Likely effects of climate change on human well-being and ecological systems
slide43

IPCC Fourth Assessment Report

Synthesis Report

Dr. R K Pachauri

Chairman

Intergovernmental Panel on Climate Change

Press Presentation

Saturday, 17 November 2007

Valencia, Spain

INTERGOVERNMENTAL PANEL ON CLIMATE CHANGE (IPCC)

bottom line on climate projections
Bottom Line on Climate Projections
  • Most warming is at high latitudes during winter months (up to 12o C)
  • Global mean warming is predicted to be 1.4-5.8o C, with stabilization at 2 x CO2 (not likely to stabilize there, though)
  • Global mean warming of 3-8o C at equilibrium CO2
  • Precipitation increases, but generally decreases over continents during the summer
    • Precipitation models are highly variable in space and among models.
    • Generally result in increased water stress
slide47

Variable

scenarios

Different scenarios focus on different human behaviors

slide50

CO2 concentrations

Double CO2

Now

slide56

BrydenH., LongwortH. & CunninghamS. Nature, 438. 665 - 657 (2005).

Nov. 30, 2005

North Atlantic current slows by 30% relative to 50 years ago.

--Driven by fresh water inputs (rain and ice melt).

--Predicted by warming models.

--Consequence: cooling in Europe.

slide58

GCM’s predict mean outcomes, but not frequencies of extreme events, making it tough to say whether recent increase in hurricane frequency and intensity is natural variation or anthropogenic

Extreme Events