The Scientific Basis of The Scientific Basis of

Global Climate ChangeGlobal Climate Change

Dr. Jim Phillips, UWEC Chemistry

For ECON 286: 3/29/13

“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!!!)

Final exam question for CHEM 127*:

History Lesson First !History Lesson First !

Svante Arrhenius: Global Warming Hypothesis

(Philosophical Magazine - 1896)

“Increased Levels of COCO22 [and other greenhouse gases] will lead to an increase in global temperature”

“Other GHG’s” include: HH22O, CHO, CH44, N, N22O, O, and Halocarbons 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!)(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?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: “FeedbacksFeedbacks” –> 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 Scienceshttp://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 humanhuman effects are included.

<— Global Temperature as modeled WITHWITH Anthropogenic Factors

<— Global Temperature as modeled WITHOUTWITHOUT 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 3) No existing model can reproduce the recent global temperature trends using recent global temperature trends using strictly natural factorsstrictly natural factors

This is how we know … This is how we know …

2007 IPCC report - Future T predictions

Key Points:

• ALL model scenarios predict warming

• Range: ~2-4°C (3-7°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)