Water Cycle: Global Circulation

• Energy input is not uniform over Earth’s surface

more heating at equator, less at poles

Latitudinal Energy Balance• Energy input&loss nonuniform over Earth’s surface

atmosphere+ocean circulation transport heat towards poles

Blackbody Radiation 1

Radiation energy R a function of the temperature of the body emitting it:

R = ( — Stefan-Boltzmann constant)

& Energy is emitted in different proportions at different frequencies (wavelengths) that also depend on the temperature of the body emitting it

[Hottest bodies emit shortest wavelength radiation (x-rays, etc.), while coolest bodies have their peak emissions in long-wavelength microwave or radiofrequencies (e.g. 2.7K big-bang relic blackbody cosmic radiation)]

T 4

Blackbody Radiation 2

Solar Radiation at Earth

Greenhouse Effect

Atmosphere ‘transparent’ to solar radiation at main wavelengths of sunlight (‘high-T blackbody radiation’)

Atmosphere absorbs radiation at infrared (‘Earth heat’) wavelengths at which the Earth emits radiation

Of the radiation energy that the atmosphere absorbs, half is re-emitted back towards the Earth’s surface, thereby warming it.

(e.g. clear nights -> cold nights, cloudy nights -> warmer nights)

No reason this couldn’t work in reverse (e.g. a material that reflected optical energy but was transparent to infrared would be cooled by an ‘inverse greenhouse’ effect)

Mean Annual Heat Balance

Atmosphere blocks incoming solar radiation AND creates greenhouse effect

23% of incoming solar energy goes into evaporating water (~1 ton/m2-year)

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Temperature Change @ all Latitudes

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Caution!• What we can now accurately measure back in time are 18O/16O and 12C/13C anomalies in fossil shells.

• These proxies can be used to ‘determine’ past temperatures and atmospheric CO2 levels that are extremely precise — but not necessarily nearly as accurate as they are precise…

• Recent glaciations can be well correlated with minor changes in the amount of sunlight reaching the northern latitudes in summer (e.g. how much winter snow can melt in the summer)

• CO2 was historically low during recent glacial times — cause or effect?

• We are now rapidly raising the global CO2 level — is this likely to be bad, good or neutral for the planet?

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Caution! Proxy & Model-based curves!

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False hockey-stick? (Wall Street Journal, Fall 2005)

Arctic Sea-Ice area down 10% last 50yrs.

Sea-Ice thickness down 40% last 50 yrs

Winter sea-ice critical to arctic bottom-water formation (ice-freezing expels cold+salty brine which sinks to seafloor)

Borehole T-increase Measurement (1)

Borehole T-increase Measurement (2)

Warming 1°C over past 5 centuries

50% of warming over past century

80% over past 2 centuries

Borehole T-increase Nonuniform

Correlation vs. Causation PitfallCausation Correlation

BUT

Correlation Causation

SEVERAL PROPOSED CAUSES FOR WARMING:

(1)Solar Variability

(2) Human-induced Greenhouse gases (generally believed by climate scientists to be the dominant cause — and still passing ever-improving tests…)

‘Political Agenda’ Pitfall(1) Real Money is at stake (Climate Change affects Wall St.)

e.g. Global Warming is only a theory, predicted effects are highly uncertain, scientists are not unanimous, data are in error, more research is needed….. AND meanwhile we should try to keep on doing business as usual…

ALTERNATIVE (environmentally conservative program)

(1) Acknowledge uncertainty is inherent

(2) Recognize it is usually easier to prevent damage than repair it later — it will cost a lot less to start now to mitigate problems than to start only when problems are becoming catastrophic... What if only a 20% chance of ‘disaster’? 10%? How would we react to this threat if it was a military threat? By doing nothing because the risk is low?

(3) Shift burden of proof away from those advocating protection to those proposing an action that may be harmful

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Sunspots

Sunspot Cycle Length vs. T since 1860

14C, 10Be: Proxies for solar activity?

15N + p (from cosmic ray) 14C + p + p (14C has 5750yr halflife)

14N + cosmic ray 10Be + 4He (10Be has 1.51My halflife)

Both 14C and 10Be rapidly rain out of atmosphere once produced in upper atmosphere.

Both are not produced by any decay processes in Earth’s interior

Sunspot Intensity vs. 14C since 1680

Maunder & Spörer Minima vs. 14C

10Be vs. 14C

10Be vs. 18O?

Does Be anomaly reflect a cause or consequence of the process causing the 18O anomaly?

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Ozone Hole — a climate success story! We can change ‘business as usual’ with a positive world-action

Ozone Hole — timeline of the social response…

Steps in the historical process of ozone ‘remediation’ by banning of CFCs as refrigerants…

(1) Ozone ‘hole’ noticed in Antarctica — increasing ozone annual minimum in upper atmosphere

(2) Theory proposed for this — catalytic effect of CFCs on ice-particles enhancing natural ozone destruction processes in the uppermost atmosphere (ozone created by solar radiation, destroyed by natural processes, amount reflects a balance between competing processes)

(3) Theory questioned — but affirmed in all tests so far.

(4) Actions finally taken to ban certain CFCs and search for different compounds that can also be used as refrigerents but which are less stable, and less catalytic

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