Body

chem 100

September 19, 2001

Focus: (finish Ch 2 notes, posted Monday)

Start Chapter 3 (Green House Gases)

Note: Exam next Wed

textbook: Ch 1-2-3
and Lecture Notes
Friday begins with exam review/summary

We discussed the Greenhouse Effect earlier

and the role of CO₂

Summary:

Many small molecules
- CO₂, H₂O, CH₄, NOx
- found in atmosphere
absorb infrared light
specifically, IR emitted/reflected by earth
- trap that energy / escapes otherwise
- leads to a warmer earth

At first, seems like a minor issue

CO₂ level is 0.03%
humans (plants, fish) heat tolerant
- we can survive -20^oC to 35^oC
- colder regions might improve w/heat
CO₂ isn't even the biggest player
- H₂O is more important
CO₂ is subject to many adjustments

Predictions are 1-3^o C in foreseeable future

much less than normal changes-- weather
much less than long term weather cycles
- earth went through ice ages w/o people
- also, primitive people survived ice ages
however, this is global, overall change

How can you predict the effect of, say, 10% increase in CO₂?

no direct effect on breathing
how to relate that to temperature
how to predict effect of 1^oC global change

Focus on CO₂ because

it is somewhat controllable
H₂O levels are not (evaporation)
- H₂O levels self stabilizing
- although small temp rise increases water level
CH₄ also somewhat controllable
- less of overall factor

The simplest model is

some CO₂ is natural (volcanoes, forest fires, elephant breath)
plants absorb this via photosynthesis
- can keep CO₂ "trapped" for years, decades, centuries
- when plant is burned, eaten, decays-- CO₂ returns
- if plant "fossilizes" we store the CO₂
modern man burns fossil fuel
- return old CO₂ to the air
photosynthesis ability is limited
- sunlight and water limits process
- clearing land decreases the process
- grasslands provide little long term storage
actually, algae are probably better than forests

Concept of an Equilibrium

Many chemical reactions are reversible
Opposite reaction will also occur
- Generally, when conditions change
Sometimes change is temperature driven
- Limestone-- mainly CaCO₃
  - calcium carbonate
- Heat CaCO3 -----> CaO + CO₂
  - calcium oxide, "quick lime"
- CaO + CO₂ -----(cool, wet) ---> CaCO₃
Sometimes the reaction is driven by concentration
- O₂ + deoxyhemoglobin ----> oxyhemoglobin
- oxyhemoglobin ---> O₂ + deoxyhemoglobin
- direction depend on O₂ levels

Another case, water
- reversible
- H₂O (liq)+ energy ---> H₂O (gas) .....evaporation
- H₂O (gas) ---> H₂O (liq) + energy .... condensation
- at Equilibrium
  - water evaporate and condenses at the same rate
  - no net change
  - individual molecules constantly changing
  - water vapor-- composition remains the same
- % Relative Humidity
  - how close to maximum level (saturation , equilibrium)

Role of CaCO₃ as a CO₂ depository

Limestone is fossil remains of mollusks and coral
Accumulated as Ca⁺² ion from water
Reacted with CO₂ in shell formation
remains after death, accumulated
pressure forms rock
last for billions of years
process continues today
- could today's clams save the world from global warming?
making concrete
- uses CaCO₃-- CO₂and CaO

Could we burn fuel but transform the CO₂?

What if we burned Coal for fuel
Mostly carbon, get lots of CO₂
Treat the CO₂ and convert into "safer" stuff?
- for example, Carbon and Oxygen
We get energy from C +O₂ --> CO₂ + heat
The reverse is often possible
But it needs that energy back
Such a power plant, if 100% effective
- produces no net power.

We do similar reactions
- electrical storage battery
- pumping water uphill to run hydroelectric generator
- all based on no net gain
  - but having power when we want it
  - perhaps utilizing low level of power over longer times

Several Critical Points

What's the basic science?
- Have we accounted for all the important variables?
How does this translate into global model?
- It is a model-- what might happen if...
- Mostly computer simulations
- Impossible to do full scale "experiments"
  - full scale needs another world
How good is the model?
- do we know and include all factors
  - are we neglecting anything significant
  - we can't include high level of detail
  - that's the advantage/drawback of models
is the method of predicting accurate
How serious is the outcome?
- Worst case /best case scenarios
- What time scale
  - Hard to get strong response unless immediate crisis

Look at air line security

Everyone in airline security knew there was serious problem
At least 20 years
Better security is costly, inconvenient and discouraging

security is a low paying job
has very high turnover (counterproductive)

Always promise of better technology (let's wait)

explosive detectors
better X-ray equipment
computer checks for "Stray" baggage
visual computer identifications

In one week, we've probably done more than in 10 years

Politics and Business deal with immediate crisis

Long term says we can wait

Policy Decisions

almost always based on incomplete information
financial manipulations
- FED adjusts interest rates
- based on questionable models
- based on predictions (not on current situation)
- that's good enough
criminal law
- conviction always based on imperfect evidence
CO₂ Treaties
- GWB-- we don't really know enough yet
- translation-- it's costly and the economy on my watch is more important
- confused (fails to separate policy and science)
  - science doesn't dictate or really recommend policy
  - science provides data, models, scenarios predictions
  - scenarios include good and bad outcomes
  - scenarios suggest behavior that is beneficial

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