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8/7/2019 Global Warming (Thomas C. Peterson, Ph.D.)
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11Climate Change 101March 12, 2007
Thomas C. Peterson
NOAAs National Climatic Data CenterAsheville, North Carolina
Climate Change 101:
An Introduction to Climate
Change Science
Climate Change 101:
An Introduction to Climate
Change Science
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22Climate Change 101March 12, 2007
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
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33Climate Change 101March 12, 2007
The nature of science
. . . science, which I define as a set ofmethods designed to describe andinterpret observed or inferred phenomena,
past or present, and aimed at building atestable body of knowledge open torejection 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
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44Climate Change 101March 12, 2007
Science is never 100% certain
Science does not deal in certainty, sofact can only mean a propositionaffirmed to such a high degree thatit would be perverse to withhold onesprovisional assent.
Stephen Jay Gould, geologist, 1999
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55Climate Change 101March 12, 2007
Science is self-correcting
In practice, contemporary scientistsusually submit their research findings
to the scrutiny of their peers, whichincludes disclosing the methods anddata which they use, so that theirresults can be checked through
replication by other scientists. IPCC 4th Assessment Report, 2007
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66Climate Change 101March 12, 2007
Competing claims, information, andeven 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
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77Climate Change 101March 12, 2007
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88Climate Change 101March 12, 2007
We need the greenhouse effect
The Earths surface temperature is~60F
Without the greenhouse effect itwould be ~5F
But humans are changing the radiativeproperties of the atmosphere andthereby the greenhouse effect
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99Climate Change 101March 12, 2007
Climate Forcing Summary
FromRavishankara (2006)
Warming versuscooling effectsare like the tortoise versusthe hare.
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1010Climate Change 101March 12, 2007
Do you believe in globalwarming?
I believe in quantum physics.
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1111Climate Change 101March 12, 2007
Quantum physics tells us that
Infrared (IR) energy can only be absorbedand radiated in very small particle-likepackets of energy called quanta
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1212Climate Change 101March 12, 2007
Quantum physics tells us that
Infrared (IR) energy can only be absorbedand radiated in very small particle-likepackets of energy called quanta
Each molecule can absorb and radiatequanta at different wavelengths
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1313Climate Change 101March 12, 2007
Quantum physics tells us that
Infrared (IR) energy can only be absorbedand radiated in very small particle-likepackets of energy called quanta
Each molecule can absorb and radiatequanta at different wavelengths
Two atom molecules can absorb very littleIR energy E.g., Nitrogen (N2) and Oxygen (O2)
98% of the atmosphere
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1414Climate Change 101March 12, 2007
Quantum physics tells us that
Infrared (IR) energy can only be absorbedand radiated in very small particle-likepackets of energy called quanta
Each molecule can absorb and radiatequanta at different wavelengths
Two atom molecules can absorb very littleIR energy E.g., Nitrogen (N2) and Oxygen (O2)
98% of the atmosphere
Three or more atom molecules do absorband radiate in the IR E.g., Carbon Dioxide (CO2), water vapor (H2O),
methane (CH4) 2% of the atmosphere CO
2only 0.04% of the atmosphere
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1515Climate Change 101March 12, 2007
Global climate models Computer
generatednumericalsimulations ofthe climate
system
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1616Climate Change 101March 12, 2007
Climate change detection andattribution
Often linked together but are twoseparate processes
Very mathematically intensive Involves the temporal and spatial
patterns of climate change
So this description is quite simplified
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1717Climate Change 101March 12, 2007
Climate change detection
Examine the instrumental temperature recordfor 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 outsidethe bounds of natural climate variability?
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1818Climate Change 101March 12, 2007
Yes, the recent observed climatechange is beyond the bounds of
natural variability
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1919Climate Change 101March 12, 2007
Attribution: What is the cause of
the detected climate change? Attribution is primarily model based
analysis
What mix of forcings is required tocreate the detected climate change?
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2020Climate Change 101March 12, 2007
Attribution example: Most of thewarming over the past 50 years is likely
due to greenhouse gas increases
IPCC TAR
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2121Climate Change 101March 12, 2007
Are CO2 and other greenhousegasses really responsible for
changing the global temperature?
Quantum physics says we shouldexpect them to be
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2222Climate Change 101March 12, 2007
Climate models say they are
Are CO2 and other greenhousegasses really responsible for
changing the global temperature?
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2323Climate Change 101March 12, 2007
Are CO2 and other greenhousegasses really responsible for
changing the global temperature? Historical observations indicate they are
related
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2424Climate Change 101March 12, 2007
Are CO2 and other greenhousegasses really responsible for
changing the global temperature? Ice cores can give us the long view
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2525Climate Change 101March 12, 2007
Are CO2 and other greenhousegasses really responsible for
changing the global temperature? The long view says they are definitely related
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2626Climate Change 101March 12, 2007
Common questions
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2727Climate Change 101March 12, 2007
You cant predict the weather 10 days inadvance, how can you predict the climate
100 years from now? Weather forecasting
and climateprojections are verydifferent Weather forecasting
is primarily basedmovements andinteractions of
weather parameters Predicting a storm 1
day late is an error
Climate projections are primarily based onthe physics of long-term changes in solarenergy and infrared radiation
The same climate physics that allow us to100% accurately predict that next summerwill be warmer than next winter
After Kiehl and Trenberth (1997)
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2828Climate Change 101March 12, 2007
Dont urban heat islands hot local temperaturescaused 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 andshows warming Increasing
temperaturessupported by: plant bloom dates
Lake/riverfreeze/thaw dates
Glaciers melting Etc.Peterson and Owen (2005)
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2929Climate Change 101March 12, 2007
Additional supporting evidence:the shrinking Arctic sea-ice
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3030Climate Change 101March 12, 2007
Dont satellites show no warming?
One satellite data setdid several years ago
As another grouptried to reproduce it,an error in the dataprocessing wasdiscovered
Both satellite andsurface datacurrently showwarming
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3131Climate Change 101March 12, 2007
What are the climateprojections 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 theIntergovernmental 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
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3232Climate Change 101March 12, 2007
Precipitation
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3333Climate Change 101March 12, 2007
Total precipitation:
From Peterson et al., 2007b
1 = ~68%2 = ~95%
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3434Climate Change 101March 12, 2007
Precipitation projections:
Totalprecipitationvery uncertain
However,modelsproject heavy
precipitationwill increaseCreated for a report due to be released in late 2007.
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3535Climate Change 101March 12, 2007
Temperature
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3636Climate Change 101March 12, 2007
Low CO2 scenario
From Peterson et al., 2007b
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3737Climate Change 101March 12, 2007
Mid-range CO2 increases
From Peterson et al., 2007b
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3838Climate Change 101March 12, 2007
Business as usual CO2
From Peterson et al., 2007b
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3939Climate Change 101March 12, 2007
Temperature projections
Projections show more change in thefuture than recently observed
Even if we stopped emitting CO2 nowthere would still be warming for thenext few decades
How warm it will be 100 years fromnow is dependent on future emissionsof greenhouse gases
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4040Climate Change 101March 12, 2007
Does anthropogenic globalwarming pass the rating criteria?
Testability Can it be proved false?
Yes, the last decade could have been cold, laboratory tests on CO2could have proven theory wrong
Fruitfulness Does it yield observable surprising predictions?
Yes, predicts increase in heavy precipitation which has beenobserved 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
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4141Climate Change 101March 12, 2007
Ockhams razor
14th
Century English Franciscan friar andphilosopher William of Ockham developed thisprinciple: 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.
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4242Climate Change 101March 12, 2007
Final comment
Stepping out into record hot weather, afriend who is an expert on climate changedetection and attribution was asked if the
high temperatures they were experiencingwere due to global warming He responded:
You cant attribute any one days temperature
to global warming But unusually warm weather like that does giveus the privilege of experiencing the weather weare bequeathing our children and grandchildren
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4343Climate Change 101March 12, 2007
Selected References
Kiehl, J., and K. Trenberth, 1997: Earths annual globalmean 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 Vzquez Aguirre, 2007a: Changes in NorthAmerican extremes derived from daily weather data.Proceedings of the National Academy of Science, inpreparation.
Peterson, Thomas C., Marjorie McGuirk, Tamara G.Houston, Andrew H. Horvitz and Michael F. Wehner,2007b: Climate Variability and Change with Implicationsfor Transportation, National Research Council, in press.
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4444Climate Change 101March 12, 2007