Werner To take your first sentence first. I've been working on the ozone-depletion issue since the early 1980s and my work does bring me in close contact with world experts at all levels of this issue, and of all disciplines. I will state categorically and with no hesitation that there is more than sufficient scientific proof that the chemical equilibrium of the so-called ozone layer has been gravely deranged by the presence of anthropogenic organic molecules containing co-valently bonded chlorine or bromine atoms. The main source of these are CFCs, halons and some other chlorocarbons or bromocarbons. That part of it is very clear cut and we know a great deal about the actual chemical mechanisms and the transtropopausal transport mechanisms for substances with an atmospheric residence time exceeding the hemispherical diffusion time (say, about 7 years). The residence time of most CFCs and halons is generally between 50 and 300 years. What is currently less clear-cut, is our knowledge concerning the comparatively minor role played by substances with a shorter residence time than 7 years. This is a much more complex subject and we are only just beginning to understand what happens with them. Take n-propyl bromide (nPB), for example. This has an atmospheric residence time of about 15 to 30 days, depending on the presence of hydroxyl radicals, temperature, barometric pressure, etc. Except for emissions within the intertropical convergence zone, where there may be a rapid transport to the ozone layer altitudes, one would think, a priori, that this substance would not present a danger to the ozone layer because it would largely decompose long before it could get there (although the decomposition follows an exponential decay curve, of course, the residence time being defined as the time taken for a given concentration to reach 1/e of its initial value). However, it is only in the last two years that we have started to understand the tropospheric chemistry of the decomposition and some of the compounds formed have a much longer residence time than the original substance. It will be only about the end of next year that we shall know the effect that such short-lived substances may have on the ozone layer but, I repeat, we do know the mechanisms for the longer-lived ones. It is estimated that the cost of determining the effect of just one substance, nPB, on the ozone layer will be in the millions, a lot of which is donated philanthropically by the panels of experts involved. If you wish to know more, read the Assessment Reports of the Science Assessment Panel, published by the UNEP. You will find any amount of info at http://www.unep.org/ozone/reports.shtml#ReportMisc . Finally, you will note that I am not relating to any of the ecopolitical extremist groups but to proven science in 2001 and not even to the more hypothetical situation that existed when the Montreal Protocol was first signed in September 1987. I agree that we are not at such a categorical stage with climate change. However, there is one document that is required reading for all persons interested in the subject. It is a 20 page report prepared by about 130 atmospheric scientists, 500 odd contributing authors and peer-reviewed by over 300 others (between them, representing about 80% of the total atmospheric scientists in the world). It is written in clear language and is well-illustrated and is meant for policymakers who are not themselves specialists. It is downloadable in pdf format (file name spm22-01.pdf) from http://www.ipcc.ch/index.html or http://www.usgcrp.gov/ipcc/ under the heading WG I "Climate Change 2001: The Scientific Basis". This clearly shows where we are in our current, up-to-date knowledge of the subject. Each statement is qualified by terms of likelihood as follows: "In this Summary for Policymakers and in the Technical Summary, the following words have been used where appropriate to indicate judgmental estimates of confidence: virtually certain (greater than 99% chance that a result is true); very likely (90-99% chance); likely (66-90% chance); medium likelihood (33-66% chance); unlikely (10-33% chance); very unlikely (1-10% chance); exceptionally unlikely (less than 1% chance). The reader is referred to individual chapters for more details." It is therefore not, in any way, categorical that we are going to fry ourselves to a crisp or that we shall have to learn to live in deep-freeze conditions or, indeed, that we shall suffer, in any way, from climate change. In other words, it takes a long, cool (pun unintended), look at what we do know, free from any political or extremist influence. And, yes, Werner, these guys do take into account what has happened in the past. Do please read this document: you will find it an hour well spent, I promise you. Best regards Brian Werner Engelmaier wrote: > > Hi Brian, > To my knowledge, the ozone depletion cause is nowhere near as clear-cut as > you ake it sound. > But back to 'global warming potential-GWP.' > Earth has gone through quite a number of climatic cycles, alternating between > cool periods and warmer [Climatic Optima] periods. Since the end of the last > glacial period, the Wisconsin or Würm Stage, about 6 to 7,000 years ago, > there have been a number of warm and even hot periods. The hot Holocene > Optimum occurred between 6 to 5,000 and 3,000 B.C., and the Little Climatiic > Optimum (LCO) or Medieval Warming Period from 750 to 1215; cold periods > occurred from 900 to 300 B.C., moderating to cool from 300 B.C. to 750 A.D. > During the LCO, ice and severe weather vanished from the Northern seas, > allowing the Vikings to expand to Iceland, Greenland [it was green, fertile, > and supported a population of 3,000 with nearly 400 farms at its height], and > Markland ["Wooded Land"--today's Labrador], and Vinland [today's > Newfoundland--where then grapes, currents, and gooseberries grew]. The LCO > also brought about the European Agricultural Revolution, with vineyards 300 > miles farther north than today, and England producing high-quality wines. > The end of the LCO spelled doom to the Viking settlements, other than > Iceland, and crop yields fell by a third throughout Europe, leading to some > of the worst famines in 1315 to 1317 and 1347, driggering the medieval > depression which lasted a century and a half and bringing the return of the > plague. > So, in history, it was the cooling, not the warming, that brought about human > disasters on a wide scale. > Those interested, may consult: Crowley, J. J., and G.R. North, > "Paleoclimatology," (Oxford, 1991), or Gimpel, J., "The Medieval Machine. The > Industrial Revolution of the Middle Ages," (N.Y., 1976), or Jones, G., "A > History of the Vikings,"(Oxford, 1984). > > Werner Engelmaier > > --------------------------------------------------------------------------------- > Technet Mail List provided as a free service by IPC using LISTSERV 1.8d > To unsubscribe, send a message to [log in to unmask] with following text in > the BODY (NOT the subject field): SIGNOFF Technet > To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL > Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives > Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional > information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 > --------------------------------------------------------------------------------- --------------------------------------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8d To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt delivery of Technet send the following message: SET Technet NOMAIL Search previous postings at: www.ipc.org > On-Line Resources & Databases > E-mail Archives Please visit IPC web site (http://www.ipc.org/html/forum.htm) for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 ---------------------------------------------------------------------------------