Climate Change
what we know
What we surmise
What 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 area
It is visible and UV light
Energy from the sun is absorbed and reemitted in
infrared 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 – uniform
Others are uniform
Absorption is in several frequencies
It 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 square
root 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 for
50 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 sink
BUT ~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?
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 his
mind!
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 that
the 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
Lindzen (1992,1994):
Climate sensitivity = 0.3±0.2oC
Figure 1.1
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
Global CO2 Emissions
Source: Energy Information Administration (WIA) International Energy Outlook 2004
(IEO 2004).
INTERNATIONAL ENERGY AGENCY
AGENCE INTERNATIONALE DE L’ENERGIE
What is the economic effect?
Here there are uncertainties
EU Nicholas Stern, now Lord Stern
Another view by
Professor William Nordhaus of Yale University
with his own model
Nordhaus and Stern Roughly
Similar per the time path of harm
• Nordhaus: Cost is equal to 3% world GDP
in 2100, 8% in 2200
• Stern: 5.3% to 13.8% in 2200
• These estimates are intended to include
not just GDP impacts, but also the value of
damages to persons and property and non
market impacts to human well being
Stern and Nordhaus disagree on how much to
spend 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
MONEY
One incentive:
millions of small decisions
Options
reduce population
reduce carbon demand
adaption
active intervention in solar flux
(geo engineering)
carbon sequestation
Anthropogenic contribution to the risk of the 2003
heat-wave
Threshold for civil
liability
Range of uncertainty
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 corn
It uses as much energy to grow corn
and upsets agriculture
“Cap and trade” with a historical cap
encourages big increases before legislation starts
selling carbon offsets
is 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 ground
ALL palcaes are recorded. COAL MINES, OIL WELLS, GAS FIELDS,
PORTS OF ENTRY
Decide 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)