Transcript Science of Climate Change

The Scientific Basis of
Global Climate Change
Dr. Jim Phillips, UWEC Chemistry
For ECON 286: 3/29/13
Final exam question for CHEM 127*:
“Concisely re-state the scientific argument that
supports the following hypothesis:
“Human activity has led to global warming”
Present this case in a systematic, logical manner.
I am looking for three specific points…
(*BTW: course is offered ON – LINE this summer!!!)
History Lesson First !
Svante Arrhenius: Global Warming Hypothesis
(Philosophical Magazine - 1896)
“Increased Levels of CO2 [and other greenhouse
gases] will lead to an increase in global
temperature”
“Other GHG’s” include: H2O, CH4, N2O, and Halocarbons
…. (Stay tuned)
#1: Average Global Temperature is Increasing
Other evidence?
Sea level up - snow & ice melting…
IPCC, AR4, WG1, 2007
NOAA, CMDL, 2009
#2: CO2 (and other GHG’s) are increasing!
C.D. Keeling and T.P. Whorf (October 2004).
Do human CO2 sources rival nature ?
(i.e.: How is that possible? the planet is so big…
or: you can’t tell me that my car is causing this…
Natural CO2 emissions:
Terrestrial Biosphere: 60.0 Pg/year
Marine Biosphere:
90.0 Pg/year
Anthropogenic CO2 emissions:
Fossil Fuels:
6.0 Pg/yr (1.5 US!)
Deforestation:
1.5 Pg/yr
Greenhouse gas concentrations:
the last 10,000 years
—> CO2 - ~35% increase
—> CH4 - more than 2x!
—> N2O - ~20% increase
Halocarbons —> ∞ increase
How do we know ? The Vostock Ice Core…
BUT DOES THIS PROOVE ANYTHING?
Nature v. 412, p. 523-527 (2 August 2001)
Let’s Back up:
3 fundamental factors that influence climate
http://earthobservatory.nasa.gov/Features/CALIPSO/CALIPSO2.php
3 Main Climate Influences means —>
3 possibilities for warming (or cooling?)
1) Incoming Solar Radiation
- Sun itself, or orbital variations
2) Reflectivity (“Albedo”)*
- Surface (land use), clouds, “Aerosols”
3) Greenhouse effect *
- H2O, CO2, CH4, N2O or Halocarbons
* Human activities have altered these 2 …
1) Incoming Solar Radiation
- Sun itself, or orbital variations
2) Reflectivity (“Albedo”)*
- Surface (land use), clouds, “Aerosols”
3 Main Climate Influences means —>
3 possibilities for warming (or cooling?)
1) Incoming Solar Radiation
- Sun itself, or orbital variations
2) Reflectivity (“Albedo”)*
- Surface (land use), clouds, “Aerosols”
3) Greenhouse effect *
- H2O, CO2, CH4, N2O or Halocarbons
* Human activities have altered these 2 …
Why things are not so simple: “Feedbacks”
–> not only are there other factors – they interact
Consider this example:
• Increased Global T —> more H2O vapor…
1) Enhanced Greenhouse —> Increased T… !
A positive feedback —> Unstable Climate
2) More clouds —> more reflected Radiation
—> Decreased T …
A negative feedback —> Stable Climate
Considerations (now back to science):
What is Scientific Proof?
What Experiment can we do?
Where IS the burden of proof ?*
*(i.e., should the scientists that “believe”
climate change is real have to bear this ?)
Figure: Courtesy of IPCC
Scientific Agencies that support work of IPCC
American Chemical Society:
http://portal.acs.org/portal/PublicWebSite/policy/publicpolicies/promote/globalclimatechange/WPCP_011538
American Geophysical Union:
http://www.agu.org/sci_pol/positions/climate_change2008.shtml
National Academy of Sciences
http://www.nasonline.org/programs/sackler-colloquia/2011-sackler-lecture.html
The list goes on …
How do we know? Models can reproduce Global
T trends - ONLY if human effects are included.
<— Global Temperature as
modeled WITH
Anthropogenic Factors
<— Global Temperature as
modeled WITHOUT
Anthropogenic Factors
Models + Observations = Causes
Key Points:
1) The planet IS getting warmer
2) CO2 and other GHG’s are by far the
dominant factor
3) No existing model can reproduce the
recent global temperature trends using
strictly natural factors
This is how we know …
2007 IPCC report - Future T predictions
Key Points:
• ALL model scenarios
predict warming
• Range: ~2-4°C (37°F)
(except “constant
composition”)
• Our choices matter
• Climate stability is
assumed by default instability may arise at
> 450 ppm CO2 ?!?!?!
Acknowledgments
Thanks for Inviting me Dr. J!!!
(thank you for your time and attention)
QUESTIONS?
COMMENTS ?
Future Global Impacts (beyond sea level)…
Here in Wisconsin… (WI DNR)
• wetter winters and drier summers with longer, hotter and
more frequent heat waves
• weather could require farmers to raise different crops
• dairy cattle beleaguered by heat exhaustion and growing
pest populations
• poorer air quality
• warmer and more shallow river waters – could hurt
populations of cold-water fish like trout
• denser algae blooms and lower oxygen levels in ponds and
lakes
• more frequent floods, droughts, forest fires and damaging
storms
• changes in tree species that could affect the forestry
industry and wildlife populations
• increases in disease-carrying insect populations
What can we do ?
•
•
•
•
•
(personal)
Hold leaders accountable for change
Conserve energy (at home, drive less, buy less, eat less)
Recycle
(state/local)
Demand cleaner energy/greater efficiency from utility co.
Land Use: reduce urban sprawl, create
pedestrian/bicycle friendly communities
(national/global)
• Get the US back at the negotiation table
• Stabilize Global population (empower women)