Climate Changewhat we know

What we surmiseWhat we Guess

What do we do about it?

Richard Wilson

Harvard University

THE EARTH IS A GREENHOUSE(Jaques Fourier 1829 Comptes Rendues)

We know the solar flux in energy per unit areaIt is visible and UV light

Energy from the sun is absorbed and reemitted ininfrared radiation by Stafan’s Law.

If the earth were not a greenhouse the temperature would be about 250 degrees Kelvin

Infrared radiation is absorbed by the upper atmosphere reemits both back to the surface and outwards.

increasing temperature by the 4th root of 2

This mechanism is fundamentally different from that of an actual greenhouse,

which works by isolating warm air inside the structure so that heat is not lost by convection.

The greenhouse effect was postulated by Jaques Fourier in 1824, [Comptes Rendues]

first infra red absorption experiments on CO2 by John Tyndall in Bristol

in 1858, and first applied quantitatively by Svante Arrhenius in 1896.

[in Philosophical Magazine]

Greenhouse gases

* water vapor, 36–70% * carbon dioxide, 9–26% * methane, 4–9% * ozone, 3–7%

Water vapor is non – uniformOthers are uniform

Absorption is in several frequenciesIt is complete at the peak of the spectrum but as T rises, the lines broaden allowing

the edges to absorb also.

This leads to an rise roughly as the squareroot of the concentration increase

Since CO2 is uniform The Temperature rise from CO2 can be

calculated IF ALL ELSE IS CONSTANT

CO2 concentrations have been measured for50 years at Muona Lua in Hawaii

They have nearly doubled in that time

about half the CO2 stays in the atmosphere(shallow oceans..vegetation)

DEEP oceans would be a huge sinkBUT ~700 year time constant

(Lindzen suggests 70 yrs)

Summer lower than winter as northern hemisphere plants absorb

As T rises water vapor changes. It probably increases leading to a change

DELTA T = DELTA T (no H2) / (1-F)

If H20 were uniform F could be calculated easily. It could be ½ or even unity

If Unity Disaster!(TIPPING POINT)

“Warming of the climate system is unequivocal”But why is it warming?

FAQ 3.1, Figure 1

The temperatures before 1950 are much less reliable and need modelling.

The E Anglia scientists had many discussions on how to describe this, and the recent interception of E mails

showed this.Public polls in US show that support for action dropped

from 70% to 35%.

But I know of no scientist who changed hismind!

Models driven with natural factors alone simulate a modest cooling over the past 50 years

Colours: Simulations with natural influences alone

Models driven with anthropogenic and natural factors are consistent with observed changes

Colours: Simulations with human and natural influences

And a third: that global temperatures follow the solar cycle length (SCL)

Friis-Christensen and Lassen, 1990

In 1985 several scientists doubted thatthe temperature rise was real

Seitz, Lindzen, Michaels,

The model predictions dropped a factor of 2 in 1990s

But now there is agreement this far

C.f. another prediction made at the time

Figure 1.1

Lindzen (1992,1994):Climate sensitivity = 0.3±0.2oC

High level of consensus on the reponse to a given emissions scenario

Michaels (2000, 2004)

Climate response to the IS92a scenario as predicted by 2001 IPCC models and by Patrick Michaels, University of Virginia

IN TE R N A TIO N A L EN E R G Y A G E N C Y A G E N C E IN TE R N A TIO N A LE D E L ’EN E R G IE

G lobal C O 2 Em issions

Source: E nergy Inform ation A dm inistration (W IA ) International E nergy O utlook 2004(IE O 2004).

What is the economic effect?Here there are uncertainties

EU Nicholas Stern, now Lord SternAnother view by

Professor William Nordhaus of Yale Universitywith his own model

Nordhaus and Stern RoughlySimilar per the time path of harm

• Nordhaus: Cost is equal to 3% world GDPin 2100, 8% in 2200

• Stern: 5.3% to 13.8% in 2200

• These estimates are intended to includenot just GDP impacts, but also the value ofdamages to persons and property and nonmarket impacts to human well being

Stern and Nordhaus disagree on how much tospend NOW for damage in 2100

(economists discount rate)Stern sets it low or zero

Nordhaus more usual (5% to 10%)Freeman Dyson tends to follow Nordhaus

If discount rate is greater than 0.1% we are already spending far too much on nuclear waste

Carbon use by any one of us affects everyone in the world a little bit

We must get a world wide approach

Who decides?Wall St?

Tyson’s Corner?I do not trust them

Croesus’ invention

MONEYOne incentive:

millions of small decisions

Options

reduce populationreduce carbon demand

adaptionactive intervention in solar flux

(geo engineering)carbon sequestation

Anthropogenic contribution to the risk of the 2003 heat-wave

Range of uncertainty

Threshold for civil liability

WHO decides?UN?

USA Congress?Environmental Activists?

Their Lawyers?Starry Eyed Academics?

It is a great playground for “pork barrel”

There are several proposed actions which are bad

Using ethanol from cornIt uses as much energy to grow corn

and upsets agriculture

“Cap and trade” with a historical capencourages big increases before legislation starts

selling carbon offsetsis analagous to 1600 popes selling indulgencies

We need an action which allows lots of individual decisions

King Croesus’ invention: MONEY

Corn Ethanol is a scam

Crucial items in the carbon cycle

Each individual in the world adds a bit to the CO2 concentration for everyone else

Within a year any carbon coming out of the ground becomes CO2

The time scale of global warming is decades

So control early as caron comes out of the groundALL palcaes are recorded. COAL MINES, OIL WELLS, GAS FIELDS,

PORTS OF ENTRYDecide on a cap.

Decrease slowly to allow adjustment (3% per year)trade permits

everyone will choose actions to minimize CO2

Probably 3 times as efficient as command and control(example USSR vs USA energy)