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I know we're chin deep in global warming rhetoric now, but can we talk about whether CO2 makes any difference at all?
The scientific consensus is that it does.
Quote:
Originally Posted by SNorman
I haven't seen much concrete evidence of how much CO2 contributes to the "greenhouse effect". Computer models that predict warming do not model the atmosphere physically based on properties of CO2 and predict energy flow, they simply have a number that is typed in that is a scientist's best "guess" as to the relationship between CO2 concentration and warming.
Hardly. Current models represent some of the most complicated computer models yet devised by man, and with the exception of a few variables we cannot control (i.e. CO2 levels) are based on the known physics of the earth and its atmosphere. The "golden standard" of the day are general circulation models. These models take into account a broad range of factors from cloud formation, to precipitation, sea absorption/release of CO2, heat transfer in the atmosphere, effects of particulates, changes in solar intensity, changes in albedo, etc.
Before a model is even considered plausible it has to accurately model the known climatic conditions of the past - i.e. from ~1880 to today, and do it accurately. Given the greater and greater knowledge we have of paleoclimate, many of these models are also being verified by modeling over those longer periods.
As for "best guess", we scientists do not guess. We enter values based on empirical observations or derived from proven processes. When we do not know a value, we run a range through to model to ensure we are not biasing our results.
Quote:
Originally Posted by SNorman
CO2 has a very narrow absorption band, so it can only absorb about 8% of the blackbody radiation sent out from the atmosphere and Earth's surface
Your number here is wrong. Most of the earths heat is released as IR energy; 71% of which is absorbed (and eventually re-emitted) by the atmosphere. CO2's spectra overlies pretty much dead-on the peak emission wavelength of the earth, meaning it can absorb a lot of heat. Of the energy captured by the atmosphere, H2O accounts for 60% of the absorbency, CO2 for ~26% with methane, N2O and O3 making up the remainder
These are commonly available values in any science or climatology textbook.
Quote:
Originally Posted by SNorman
no matter how much of it is there. Also, it absorbs completely within the atmosphere at those narrow absorbtion bands, so there is no IR "escaping" right now that would be held in the atmosphere longer by more CO2.
Absolutely false. Absorption is far from 100%; so quite a bit of IR light escapes earth - it must, otherwise the surface of the planet would continually heat up.
Quote:
Originally Posted by SNorman
There's also the view that atmospheric CO2 is rising because of slightly higher ocean temps, which in turn dissolve less CO2.
Conventional scientific thinking see's the problem as the opposite - the warming of the earth ahs reduced the oceans CO2 holding capabilities, as gas absorbance in water drops as temperatures increase. As a result the ocean can absorb less CO2, thus amplifying the buildup of CO2 in the atmosphere.
Well established sites who's aim is to refute global warming, regardless of what the science says.
For far better info try RealClimate, a webpage run by actual climatologists who are actually involved in climatic research. The best sign of its credibility is they are as likely to tear into papers which support GW as they are likely to tear anti-warming research appart.
The warmest year on record is now 1934. 1998 (long trumpeted by the media as record-breaking) moves to second place. 1921 takes third. In fact, 5 of the 10 warmest years on record now all occur before World War II
For the USA, but not for the world.
Bryan
__________________
My homepage - www.warthaug.com - articles on SCUBA, the outdoors, and science.
BUT, why is everyone so sure that warming is a bad thing?
Off the top of my head:
1) Massive loss of the most highly populated places on earth - the areas neighboring the sea.
2) The drying out of several of the worlds "bread baskets"
3) Increased weather severity, potentially combined with increased rates of storms
4) Mass extinction of animal and plant species
Quote:
Originally Posted by Hank49
Other than I'll lose my beach lot up on San Pedro....There are some postives. The major concern is food production. The world has to eat. A warmer overal climate could be a positive in that regard with year round production in the temperate zones. All I hear is doom and gloom associated with warming. Why?
Because all of the climatic models agree that the warming we expect to see will have a net downward effect on crop production, not benefit. Keep in mind that the kinds of temperature changes we're talking about are not going to open up vast new area of the earth to farming. Instead we expect to see changes in rainfall and storm patterns, and unfortunately all evidence suggests that todays major agricultural areas are in for poorer growing conditions, not better.
Bryan
__________________
My homepage - www.warthaug.com - articles on SCUBA, the outdoors, and science.
With great respect, Bryan, given the sum total of what we do not yet know regarding the atmosphere on this planet and the manner in which its myriad variables (known and not yet known) interact with one another, the more alarmist conclusions being trumpeted in the media regarding predicted outcomes of climate change sound positively Malthusian.
I would like to return to Tassie's post a page back or so, and inquire into your (and Dr. Rohan's) thoughts regarding a sentence he wrote:
Quote:
Originally Posted by Tassie Rohan
"There have been periods where there has been huge ice sheets covering most land masses (and we are still not fully sure how they melted as the albedo effect reflects heat)."
Given that the data appear to suggest that the ice sheets which previously covered the planet periodically throughout its known history were rather substantial, extending nearly to the equator in some instances and of significant thicknesses, what melted them?
Mankind's influence had yet to manifest itself.
It would appear that throughout the planet's history periods of intense cooling have been followed, cyclically, by periods of intense warming.
Allowing for even significant climatic degradation recently caused - to some extent - by mankind's deplorable abuse of natural resources, could it not also be that a cyclical period of warming may also naturally be occurring?
__________________
Qui desiderat pacem, praeparet bellum. Flavius Vegetius Renatus, "De Re Militari" (390 AD)
Let him who wishes for peace prepare for war. How far do you want to go?http://www.ted.com/index.php/talks/view/id/141
2) The drying out of several of the worlds "bread baskets"
3) Increased weather severity, potentially combined with increased rates of storms
4) Mass extinction of animal and plant species
Because all of the climatic models agree that the warming we expect to see will have a net downward effect on crop production, not benefit. Keep in mind that the kinds of temperature changes we're talking about are not going to open up vast new area of the earth to farming. Instead we expect to see changes in rainfall and storm patterns, and unfortunately all evidence suggests that todays major agricultural areas are in for poorer growing conditions, not better.
Bryan
So we slowly change to aquaculture as a main food source.
Mass extinction...I know..it's a shame but at this pace, it's inevitable.
Rainfall? Warmer temps mean more oceanic evaporation doesn't it? That has to fall somewhere. Warm regions, the tropics, tend to be wet, cold regions more dry. Flood or drought conditions mean we need more water storage capacity, and hydro power. Sorry for the salmon and other organisms that can't make it back to their upland waters but.....
Some places may dry out, others will get wetter. Genetically improved, faster growing, intensive culture tolerant crops will need be developed, which is already happening.
Whether or not the climatic predictions are accurate or not, we'd best prepare for a big change because I don't think it's in our power, politically or physically, to stop the process.
I know we're chin deep in global warming rhetoric now, but can we talk about whether CO2 makes any difference at all? I haven't seen much concrete evidence of how much CO2 contributes to the "greenhouse effect". Computer models that predict warming do not model the atmosphere physically based on properties of CO2 and predict energy flow, they simply have a number that is typed in that is a scientist's best "guess" as to the relationship between CO2 concentration and warming.
CO2 has a very narrow absorption band, so it can only absorb about 8% of the blackbody radiation sent out from the atmosphere and Earth's surface no matter how much of it is there. Also, it absorbs completely within the atmosphere at those narrow absorbtion bands, so there is no IR "escaping" right now that would be held in the atmosphere longer by more CO2.
There's also the view that atmospheric CO2 is rising because of slightly higher ocean temps, which in turn dissolve less CO2.
The warmest year on record is now 1934. 1998 (long trumpeted by the media as record-breaking) moves to second place. 1921 takes third. In fact, 5 of the 10 warmest years on record now all occur before World War II
You don't believe global warming? It's certain that CO2 is responsible, you can see Venus, a planet who has 95% of CO2 and the temperature is 900°F.
The scientific consensus is that it does.
Your number here is wrong. Most of the earths heat is released as IR energy; 71% of which is absorbed (and eventually re-emitted) by the atmosphere. CO2's spectra overlies pretty much dead-on the peak emission wavelength of the earth, meaning it can absorb a lot of heat. Of the energy captured by the atmosphere, H2O accounts for 60% of the absorbency, CO2 for ~26% with methane, N2O and O3 making up the remainder
I'm sorry, I have to respecfully disagree. CO2 aborbs it's main peak of IR at 15µM in 10 meters of atmosphere. Other bands are absorbed within 300 meters.
Compared to entire blackbody IR spectrum:
I'm sorry, if you don't understand what this means you're going to have to either brush up on your physics or this debate is useless. CO2 absorbs a relatively small portion of IR released from the Earth. It cannot possibly aborb the entire blackbody spectrum so even if the atmosphere was 100% CO2 most of the radation would leave.
By the way do you know what context your numbers came from re: H2O being responsible for 60% of absorbency? The figures differ depending on atmosphere location (troposphere, stratosphere, etc). Most estimates I see of the atmosphere *as a whole*, including clouds (yes, people who want to skew statistics will list "water vapor" absorbency and leave out clouds) show 90% absorbtion by water and 10% CO2.
Hardly. Current models represent some of the most complicated computer models yet devised by man, and with the exception of a few variables we cannot control (i.e. CO2 levels) are based on the known physics of the earth and its atmosphere. The "golden standard" of the day are general circulation models. These models take into account a broad range of factors from cloud formation, to precipitation, sea absorption/release of CO2, heat transfer in the atmosphere, effects of particulates, changes in solar intensity, changes in albedo, etc.
By the way, current models are unable to correctly show what temperature the Earth would be at with no GW gasses present.
There are ominous signs that the Earth’s weather patterns have begun to change dramatically and that these changes may portend a drastic decline in food production – with serious political implications for just about every nation on Earth. The drop in food output could begin quite soon, perhaps only 10 years from now. The regions destined to feel its impact are the great wheat-producing lands of Canada and the U.S.S.R. in the North, along with a number of marginally self-sufficient tropical areas – parts of India, Pakistan, Bangladesh, Indochina and Indonesia – where the growing season is dependent upon the rains brought by the monsoon.
