• Have out B.4/B.7 worksheet• Objective: Describe the relationship between global

dimming and global warming.• Catalyst: Why does global dimming occur only during the

daylight hours, while global warming occurs both during day and night?

• Homework: Read lab B.6 Specific Heat Capacity, page 346. – Answer: What is the goal of the lab? What concept/idea

will we use to accomplish this goal?– Create a flow chart for the procedure of the lab. Do not

simply copy steps from the book. – Create a data table that you will use to record data during

the lab.

B.4

• Thermal Properties– Reflectivity: Light colors reflect more light than

dark colors and stay cooler– Specific Heat Capacity: Materials with higher

SHC store more thermal energy and are slower to heat up and slower to cool down (water!)

Assignment

• Do B.5 and B.8 on the same page. You may work in groups of 2 and use the same paper.

Climate Change (a.k.a. Global Warming)

Key Indicators & Evidence

• Carbon Dioxide Concentration• Global Surface Temperature• Artic Sea Ice• Land Ice• Sea Level• Glacial Melting Rates• Growing Seasons• Major Precipitation Events

Other Evidence of Climate Change

Increases inGlacial MeltingRates

Other Evidence of Climate Change

Growing Seasons Lengthening

A recent study of European spring and autumn plant phases indicates that on average, spring events advanced by about six days and autumn events were delayed by about five days over the period from 1959 to 1993 (Menzel and Fabian, 1999). The long-term consequences of these changes are uncertain. The changing climate may impair the extent to which an animal’s life cycle is synchronized with its food supply. Birds, for example, can adjust to warmer temperatures by flying to more northern areas in any given year, but the vegetation upon which they (or their prey) rely may take decades or longer to adjust (see Root, 1997).

Other Evidence of Climate Change

Keep in Mind:• Evidence is sometimes anecdotal• We don’t have controlled experiments• Difficult to determine causal connection• does increased [GHGs] Hurricane Y

4 major reasons• Variations in Earth’s orbit• Solar variation• Non-human changes in GHG concentrations• Position of continents versus oceans

Why would climates change in past?

Feedbacks in Climate Change

Negative feedbacks—results in LESS global warming• Global warming (GW) expansion of algae populations in ocean

greater uptake of CO2 • Higher [CO2] more plant growth greater uptake of CO2 • GW more evaporation more clouds less solar input

Positive feedbacks—results in MORE global warming• GW more evaporation more water vapor

more IR reradiation • GW reduction of snowpack less light reflection • GW more energy use higher GHG emissions

(more air conditioning but less heating?)

Sources of information on climate change

1. Evaluation of geologic record• What does the distant past tell us?

2. Monitoring of present record• What does recent data tell us?

3. Mathematical models• Can we model the atmosphere and make predictions?• What do these models tell us about the future?

The Geologic Record & Climate Change

We use proxies (time capsules):

• sediment cores in oceans – certain unicellular species live in

waters with specific temperatures– <250 million years (age of oceans)

• glacial ice• CO2 bubbles trapped in ice • <500,000 years

• tree rings – thickness of rings (dendrochronology); thick = high T, water avail. – < 1,200 years

• pollen records – plants live in certain T. regimes – ~10-20 Kyrs

The Geologic Record & Climate Change

More proxies:

Sunflower

Ragweed

What do proxies tell us?

1. Last 2.5 million years, T’s have varied 4-10°C

2. Last 160 Kyrs, [CO2] =190-290 ppm (currently ~380 ppm)

3. Last million+ years, peak T was 1-2°C warmer than today.

The Earth has had these temperatures before, but never this much CO2.

Low level change is as equally likelyas a high level change.

PREDICTED FUTURETEMPERATURE CHANGE

There is a danger in taking “risk,” given that:

• we are near the peak Earth T. of the past 2 Myr

• ecosystems are already stressed in other ways:

pollution (pesticides/synthetic chemicals), depleted fisheries &

deforestation, dams/roads, invasive species

• locations most vulnerable to changes are currently in the worst

position to respond/adapt (e.g., continent of Africa & Oceania)

Additional reasons to be concerned about climate change:

These thoughts lead to:

“Where there are threats of serious or irreversible environmental damage, lack of full scientific certainty shall not be used as a reason for postponing cost effective measures to prevent environmental degradation.”

• “Better safe than sorry.”• “A ounce of prevention is worth a pound of

cure.”

“Where there are threats of serious or irreversible environmental damage, lack of full scientific certainty shall not be used as a reason for postponing cost effective measures to prevent environmental degradation.”

ReviewData• CO2

• Surf. Temp.• Sea Ice• Land Ice• Sea Level• Extreme weather• Glaciers melting• Growing seasons

lengthened

Historical Climate Change• Variations in Earth’s orbit• Solar variation• Non-human changes in GHG concentrations• Position of continents versus oceansFeedback Systems• Negative• Positive

Consequences • Increase sea levels• More severe weather• Elongated growing season

Gathering Info• Current measurements• Historical proxies• Mathematical models

Essay (Due 5/31 or 6/1)• Intro, conclusion and as follows– What are the possible causes of global dimming?– What is the evidence that global dimming occurs?– What tools and techniques are used to study global

dimming?– How is global dimming causing scientists to re-evaluate

current climate models?– What can be done to reduce global dimming? Should

these steps be taken without also addressing global warming? Why or why not?

• Should be typed and printed out and well-written!• No more than 3 pages double-spaced. Write

clearly and to the point!

Lab Report: Formal excluding Intro and Procedure (Due 6/4 or 6/5)

• You do not need to do Intro, Procedure• You do need to do Data, analysis, and

conclusion including book questions• Must be typed