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Thomas C. Peterson

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Climate Change 101: An Introduction to Climate Change Science Thomas C. Peterson NOAA s National Climatic Data Center Asheville, North Carolina – PowerPoint PPT presentation

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Title: Thomas C. Peterson


1
Climate Change 101 An Introduction to Climate
Change Science
Thomas C. Peterson NOAAs National Climatic
Data Center Asheville, North Carolina
2
Outline of the talk
  • The nature of science
  • The greenhouse effect
  • The physics of climate change
  • Global climate models
  • Climate change detection and attribution
  • Common questions
  • Concluding comments

3
The nature of science
  • . . . science, which I define as a set of methods
    designed to describe and interpret observed or
    inferred phenomena, past or present, and aimed at
    building a testable body of knowledge open to
    rejection or confirmation. In other words,
    science is a specific way of analyzing
    information with the goal of testing claims.
  • Michael Shermer, director of Skeptics Society,
    1997

4
Science is never 100 certain
  • Science does not deal in certainty, so fact can
    only mean a proposition affirmed to such a high
    degree that it would be perverse to withhold
    ones provisional assent.
  • Stephen Jay Gould, geologist, 1999

5
Science is self-correcting
  • In practice, contemporary scientists usually
    submit their research findings to the scrutiny of
    their peers, which includes disclosing the
    methods and data which they use, so that their
    results can be checked through replication by
    other scientists.
  • IPCC 4th Assessment Report, 2007

6
Competing claims, information, and even
misinformation can be assessed
  • Testability
  • Can it be proved false?
  • Fruitfulness
  • Does it yield observable surprising predictions?
  • Scope
  • How many different phenomena does it explain?
  • Simplicity
  • How many assumptions does it make?
  • Conservatism
  • Is it consistent with our well founded beliefs?
  • Theodore Schick, Jr. Lewis Vaughn,
    philosophers, 2001

7
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8
We need the greenhouse effect
  • The Earths surface temperature is 60ºF
  • Without the greenhouse effect it would be 5ºF
  • But humans are changing the radiative properties
    of the atmosphere and thereby the greenhouse
    effect

9
Climate Forcing Summary
From Ravishankara (2006)
Warming versus cooling effects are like the
tortoise versus the hare.
10
Do you believe in global warming?
  • I believe in quantum physics.

11
Quantum physics tells us that
  • Infrared (IR) energy can only be absorbed and
    radiated in very small particle-like packets of
    energy called quanta

12
Quantum physics tells us that
  • Infrared (IR) energy can only be absorbed and
    radiated in very small particle-like packets of
    energy called quanta
  • Each molecule can absorb and radiate quanta at
    different wavelengths

13
Quantum physics tells us that
  • Infrared (IR) energy can only be absorbed and
    radiated in very small particle-like packets of
    energy called quanta
  • Each molecule can absorb and radiate quanta at
    different wavelengths
  • Two atom molecules can absorb very little IR
    energy
  • E.g., Nitrogen (N2) and Oxygen (O2)
  • 98 of the atmosphere

14
Quantum physics tells us that
  • Infrared (IR) energy can only be absorbed and
    radiated in very small particle-like packets of
    energy called quanta
  • Each molecule can absorb and radiate quanta at
    different wavelengths
  • Two atom molecules can absorb very little IR
    energy
  • E.g., Nitrogen (N2) and Oxygen (O2)
  • 98 of the atmosphere
  • Three or more atom molecules do absorb and
    radiate in the IR
  • E.g., Carbon Dioxide (CO2), water vapor (H2O),
    methane (CH4)
  • 2 of the atmosphere
  • CO2 only 0.04 of the atmosphere

15
Global climate models
  • Computer generated numerical simulations of the
    climate system

16
Climate change detection and attribution
  • Often linked together but are two separate
    processes
  • Very mathematically intensive
  • Involves the temporal and spatial patterns of
    climate change
  • So this description is quite simplified

17
Climate change detection
  • Examine the instrumental temperature record for
    the last 100 years
  • Examine the paleoclimate record for the past 1000
    or 2000 years
  • Examine climate model control runs
  • No changes in forcing
  • Run for 10,000s of years
  • Is the recent observed climate change outside the
    bounds of natural climate variability?

18
Yes, the recent observed climate change is beyond
the bounds of natural variability
19
Attribution What is the cause of the detected
climate change?
  • Attribution is primarily model based analysis
  • What mix of forcings is required to create the
    detected climate change?

20
Attribution example Most of the warming over the
past 50 years is likely due to greenhouse gas
increases
IPCC TAR
21
Are CO2 and other greenhouse gasses really
responsible for changing the global temperature?
  • Quantum physics says we should expect them to be

22
Are CO2 and other greenhouse gasses really
responsible for changing the global temperature?
  • Climate models say they are

23
Are CO2 and other greenhouse gasses really
responsible for changing the global temperature?
  • Historical observations indicate they are related

24
Are CO2 and other greenhouse gasses really
responsible for changing the global temperature?
  • Ice cores can give us the long view

25
Are CO2 and other greenhouse gasses really
responsible for changing the global temperature?
  • The long view says they are definitely related

26
Common questions
27
You cant predict the weather 10 days in advance,
how can you predict the climate 100 years from
now?
  • Weather forecasting and climate projections are
    very different
  • Weather forecasting is primarily based movements
    and interactions of weather parameters
  • Predicting a storm 1 day late is an error

After Kiehl and Trenberth (1997)
  • Climate projections are primarily based on the
    physics of long-term changes in solar energy and
    infrared radiation
  • The same climate physics that allow us to 100
    accurately predict that next summer will be
    warmer than next winter

28
Dont urban heat islands hot local temperatures
caused by buildings and concrete- make U.S. and
global temperatures unreliable?
  • No
  • The urban effect is minor with land data
  • Ocean data has no urban effect and shows warming
  • Increasing temperatures supported by
  • plant bloom dates
  • Lake/river freeze/thaw dates
  • Glaciers melting
  • Etc.

Peterson and Owen (2005)
29
Additional supporting evidence the shrinking
Arctic sea-ice
30
Dont satellites show no warming?
  • One satellite data set did several years ago
  • As another group tried to reproduce it, an error
    in the data processing was discovered
  • Both satellite and surface data currently show
    warming

31
What are the climate projections for my area?
  • Models arent accurate at city level
  • But can use projections for a large region such
    as the Eastern US
  • Projections are not from the Intergovernmental
    Panel on Climate Change (IPCC)
  • But based on all the models that were run to
    contribute to the IPCC
  • Over 25 models
  • Three emission scenarios

32
Precipitation
33
Total precipitation
1s 68 2s 95
From Peterson et al., 2007b
34
Precipitation projections
  • Total precipitation very uncertain
  • However, models project heavy precipitation will
    increase

Created for a report due to be released in late
2007.
35
Temperature
36
Low CO2 scenario
From Peterson et al., 2007b
37
Mid-range CO2 increases
From Peterson et al., 2007b
38
Business as usual CO2
From Peterson et al., 2007b
39
Temperature projections
  • Projections show more change in the future than
    recently observed
  • Even if we stopped emitting CO2 now there would
    still be warming for the next few decades
  • How warm it will be 100 years from now is
    dependent on future emissions of greenhouse gases

40
Does anthropogenic global warming pass the rating
criteria?
  • Testability
  • Can it be proved false?
  • Yes, the last decade could have been cold,
    laboratory tests on CO2 could have proven theory
    wrong
  • Fruitfulness
  • Does it yield observable surprising predictions?
  • Yes, predicts increase in heavy precipitation
    which has been observed
  • Scope
  • How many different phenomena does it explain?
  • Changes in temperature, precipitation,
    atmospheric circulation, storms, mountain glacier
    melting, arctic sea-ice melting, etc.
  • Simplicity
  • How many assumptions does it make?
  • None, based on quantum physics
  • Conservatism
  • Is it consistent with our well founded beliefs?
  • Yes, no previously unknown phenomena are required
    to explain it

41
Ockhams razor
  • 14th Century English Franciscan friar and
    philosopher William of Ockham developed this
    principle
  • All things being equal, the simplest solution
    tends to be the best one.
  • Greenhouse gases warming the planet is simple
  • Alternate climate change explanations are not
  • Require ignoring CO2s radiative effect
  • Paying attention to unproven explanations
  • It is just part of a natural cycle (that doesnt
    show up in the paleoclimate record)
  • It is all due to changes in solar geomagnetism
  • It is all due to urban contamination of data sets
  • A negative feedback like the cloud-iris effect
    will save us
  • It is all due to cosmic rays
  • Etc.

42
Final comment
  • Stepping out into record hot weather, a friend
    who is an expert on climate change detection and
    attribution was asked if the high temperatures
    they were experiencing were due to global warming
  • He responded
  • You cant attribute any one days temperature to
    global warming
  • But unusually warm weather like that does give us
    the privilege of experiencing the weather we are
    bequeathing our children and grandchildren

43
Selected References
  • Kiehl, J., and K. Trenberth, 1997 Earths annual
    global mean energy budget. Bull. Amer. Meteor.
    Soc., 78, 197-206.
  • Peterson, Thomas C. and Timothy W. Owen, 2005
    Urban Heat Island Assessment Metadata are
    Important. Journal of Climate, 18, 2637-2646.
  • Peterson, Thomas C., Xuebin Zhang, Manola Brunet
    India, Jorge Luis Vázquez Aguirre, 2007a Changes
    in North American extremes derived from daily
    weather data. Proceedings of the National Academy
    of Science, in preparation.
  • Peterson, Thomas C., Marjorie McGuirk, Tamara G.
    Houston, Andrew H. Horvitz and Michael F. Wehner,
    2007b Climate Variability and Change with
    Implications for Transportation, National
    Research Council, in press.

44
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