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 [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±0.2 o C

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

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

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 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 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)