Vapour Trails and Greenhouse Gas
Thread Starter
Join Date: Jul 2003
Location: No Fixed Address
Posts: 30
Likes: 0
Received 0 Likes
on
0 Posts
Vapour Trails and Greenhouse Gas
I was reading an old copy of New Scientist magazine and came across an interesting article...
Aircraft vapour trails are climate scourge
Airlines could boost their emissions of the greenhouse gas carbon dioxide and still halve their impact on global warming. That is the paradoxical conclusion of a new study into the effects of commercial aviation on the environment.
Eliminating contrails offsets extra CO2 from engines.
The CO2 emitted from their engines is not the only way aircraft affect climate. They also do so through their contrails, the long trails of water vapour and ice that form in an aircraft's wake and which can persist for several hours. Contrails trap heat in the atmosphere by reflecting infrared radiation emitted from the Earth's surface.
In 1999 the Intergovernmental Panel on Climate Change (IPCC) calculated that contrails from the world fleet of 12,000 civil airliners contribute as much to global warming as the CO2 their engines pour out as they burn jet fuel.
But global air traffic is growing by around 3.5 per cent per year, and many of those extra flights are long-haul, high-altitude, contrail-forming journeys. So by 2050 contrails will be having a great deal more of an impact on global warming than the CO2 emissions from aircraft engines.
Contrails could be eliminated if aircraft reduced their altitude from about 33,000 feet to between 24,000 feet and 31,000 feet, depending on the weather.
But this would come at a price: lower altitude means denser air and higher air resistance, so planes have to burn more fuel. And this means more CO2 emissions, which would apparently negate any benefits from eliminating contrails.
But according to researchers at Imperial College, London, the idea may work after all. "It seems counterintuitive," admits Robert Noland, one of the authors of the study. But Noland and his colleagues have calculated that if planes flew low enough to leave no contrails behind, their fuel consumption would increase by only four per cent, boosting CO2 emissions by the same amount.
The team based their calculations on a simulation of a year's worth of traffic over the busiest part of Europe, taking into account the need for different aircraft to fly at different altitudes to avoid collisions.
But the proposed trade-off between cumulative CO2 emissions and short-lived contrails should be approached with caution, says Ben Matthews, a climate researcher at the Catholic University of Leuven, in Belgium.
"Such a policy might reduce the warming in the short term in regions where most planes are flying, but still increase the warming in the longer term in southern developing countries," he says.
And the Imperial team admits that reducing altitudes may not be a cure-all, since its burden on air traffic controllers has yet to be fully assessed.
T.B
Aircraft vapour trails are climate scourge
Airlines could boost their emissions of the greenhouse gas carbon dioxide and still halve their impact on global warming. That is the paradoxical conclusion of a new study into the effects of commercial aviation on the environment.
Eliminating contrails offsets extra CO2 from engines.
The CO2 emitted from their engines is not the only way aircraft affect climate. They also do so through their contrails, the long trails of water vapour and ice that form in an aircraft's wake and which can persist for several hours. Contrails trap heat in the atmosphere by reflecting infrared radiation emitted from the Earth's surface.
In 1999 the Intergovernmental Panel on Climate Change (IPCC) calculated that contrails from the world fleet of 12,000 civil airliners contribute as much to global warming as the CO2 their engines pour out as they burn jet fuel.
But global air traffic is growing by around 3.5 per cent per year, and many of those extra flights are long-haul, high-altitude, contrail-forming journeys. So by 2050 contrails will be having a great deal more of an impact on global warming than the CO2 emissions from aircraft engines.
Contrails could be eliminated if aircraft reduced their altitude from about 33,000 feet to between 24,000 feet and 31,000 feet, depending on the weather.
But this would come at a price: lower altitude means denser air and higher air resistance, so planes have to burn more fuel. And this means more CO2 emissions, which would apparently negate any benefits from eliminating contrails.
But according to researchers at Imperial College, London, the idea may work after all. "It seems counterintuitive," admits Robert Noland, one of the authors of the study. But Noland and his colleagues have calculated that if planes flew low enough to leave no contrails behind, their fuel consumption would increase by only four per cent, boosting CO2 emissions by the same amount.
The team based their calculations on a simulation of a year's worth of traffic over the busiest part of Europe, taking into account the need for different aircraft to fly at different altitudes to avoid collisions.
But the proposed trade-off between cumulative CO2 emissions and short-lived contrails should be approached with caution, says Ben Matthews, a climate researcher at the Catholic University of Leuven, in Belgium.
"Such a policy might reduce the warming in the short term in regions where most planes are flying, but still increase the warming in the longer term in southern developing countries," he says.
And the Imperial team admits that reducing altitudes may not be a cure-all, since its burden on air traffic controllers has yet to be fully assessed.
T.B
Join Date: Sep 2000
Location: Scottsdale, AZ USA
Posts: 728
Likes: 0
Received 0 Likes
on
0 Posts
"Contrails trap heat in the atmosphere by reflecting infrared radiation emitted from the Earth's surface."
I believe just the opposite of a study commisioned after 9-11.
The minimal airtraffic immediately after 9-11 proved conclusively how contrails coallesce into high Cirrus. The beliefs expressed by the researchers was that while the clouds may trap some heat in, they also serve as an umbrella reflecting much IR radiation out.
More study required for sure.
PT
I believe just the opposite of a study commisioned after 9-11.
The minimal airtraffic immediately after 9-11 proved conclusively how contrails coallesce into high Cirrus. The beliefs expressed by the researchers was that while the clouds may trap some heat in, they also serve as an umbrella reflecting much IR radiation out.
More study required for sure.
PT
Join Date: Aug 2000
Location: UK
Posts: 1,914
Likes: 0
Received 0 Likes
on
0 Posts
<<Contrails could be eliminated if aircraft reduced their altitude from about 33,000 feet to between 24,000 feet and 31,000 feet...... if planes flew low enough to leave no contrails behind, their fuel consumption would increase by only four per cent>>
These people don't know what they are talking about. When climate scientists decide to look into areas not their expertise, then they come out with garbage like this. Had to fly back from MIA unexpectedly below 29,000' all the way instead of 33-39,000'. We used a darn sight more than 4% extra. To go even further down to 24,000'- we would not have made it- the differential would be large. Their figures are nonsense, so don't trust the rest of it! I shouldn't give it any further thought!
These people don't know what they are talking about. When climate scientists decide to look into areas not their expertise, then they come out with garbage like this. Had to fly back from MIA unexpectedly below 29,000' all the way instead of 33-39,000'. We used a darn sight more than 4% extra. To go even further down to 24,000'- we would not have made it- the differential would be large. Their figures are nonsense, so don't trust the rest of it! I shouldn't give it any further thought!
Guest
Posts: n/a
I'm definitely not a Chemtrails person!
Anyway, the paper to which the New Scientist article refers is this one:
'Reducing the climate change impacts of aviation by restricting cruise altitudes'
Transportation Research Part D: Transport and Environment, Volume 7, Issue 6, November 2002, Pages 451-464
Victoria Williams, Robert B. Noland and Ralf Toumi
I have an electronic copy of the paper on my screen.
To clarify, the calculated increased fuel burns are the result of a complex simulation using a reorganized air traffic control mathematical simulator (RAMS) for Europe only (i.e. it may be weighted towards short haul flights and it also appears to allow for a reorganization of the air traffic management structure). They concede that their simulations produced variable outputs depending on the parameters, including a 7.2% increase under some circumstances. 3.9% is the weighted mean.
Note that the conclusions do not advocate that such a reorganisation of air traffic should be undertaken, just that the results are interesting:
'The results presented here indicate that a strategy to avoid the production of contrails by restricting cruise altitude could provide a net benefit to climate, despite the associated increase in CO2 emission. The analysis suggests that the implications for controller workload present the most likely operational obstacles to such a scheme and that reconfiguration of airspace would be required to mitigate the impacts.'
The study of the effects on surface temperature of Sept 11th is this one:
Nature Volume 418(6898) 8 August 2002 p 601
Climatology: Contrails reduce daily temperature range
Travis, David J.*; Carleton, Andrew M.†; Lauritsen, Ryan G.*
Again, I have a copy.
They conclude:
'Our findings indicate that the diurnal temperature range averaged across the United States was increased during the aircraft-grounding period, despite large variations in the amount of cloud associated with mobile weather systems (Fig. 2). We argue that the absence of contrails was responsible for the difference between a period of above-normal but unremarkable DTR and the anomalous conditions that were recorded.'
In other words, there was clear evidence that contrails affect short term surface temperatures. No conclusions were drawn about the impact on global warming, but it does not seem unreasonable to hypothesise that the contrails have some role to play, be it positive or negative in terms of anthropogenic heating.
With regard to the science, the Intergovernmental Panel on Climate Change (IPCC) studied the role of aviation in global warming in detail (and continue to do so). Their detailed report is here:
http://www.grida.no/climate/ipcc/aviation/index.htm
With regards to contrails they said in the summary (there is more detail in the report)
( http://www.grida.no/climate/ipcc/aviation/007.htm#spm45 ):
4.5. Contrails
In 1992, aircraft line-shaped contrails are estimated to cover about 0.1% of the Earth’s surface on an annually averaged basis with larger regional values. Contrails tend to warm the Earth’s surface, similar to thin high clouds. The contrail cover is projected to grow to 0.5% by 2050 in the reference scenario (Fa1), at a rate which is faster than the rate of growth in aviation fuel consumption.
This faster growth in contrail cover is expected because air traffic will increase mainly in the upper troposphere where contrails form preferentially, and may also occur as a result of improvements in aircraft fuel efficiency...The radiative effect of contrails depends on their optical properties and global cover, both of which are uncertain. Contrails have been observed as line-shaped clouds by satellites over heavy air traffic areas and covered on average about 0.5% of the area over Central Europe in 1996 and 1997.
4.6. Cirrus Clouds
Extensive cirrus clouds have been observed to develop after the formation of persistent contrails. Increases in cirrus cloud cover (beyond those identified as line-shaped contrails) are found to be positively correlated with aircraft emissions in a limited number of studies. About 30% of the Earth is covered with cirrus cloud. On average an increase in cirrus cloud cover tends to warm the surface of the Earth. An estimate for aircraft-induced cirrus cover for the late 1990s ranges from 0 to 0.2% of the surface of the Earth. For the Fa1 scenario, this may possibly increase by a factor of 4 (0 to 0.8%) by 2050; however, the mechanisms associated with increases in cirrus cover are not well understood and need further investigation.
To say that these scientists do not know what they are talking about on the basis of third hand information would seem to be somewhat naive. Read their reports first-hand (all IPCC reports are available online for example), then make a decision.
This is a serious issue for aviation. The vast majority of climate scientists now accept that some anthropogenic global warming is occurring (IPCC involves about 1000 experts from universities, research centres, business and environmental associations, and other organizations in approximately 120 countries). As a result, the pressure to see reductions of change-causing processes is going to increase in the future. Aviation would be well-advised to act in a pre-emptive manner rather than have regulation imposed upon it. Burying our collective head in the sand is an unwise policy, whether you believe in the science or not.
Apologies for the long post
DrDave
Anyway, the paper to which the New Scientist article refers is this one:
'Reducing the climate change impacts of aviation by restricting cruise altitudes'
Transportation Research Part D: Transport and Environment, Volume 7, Issue 6, November 2002, Pages 451-464
Victoria Williams, Robert B. Noland and Ralf Toumi
I have an electronic copy of the paper on my screen.
To clarify, the calculated increased fuel burns are the result of a complex simulation using a reorganized air traffic control mathematical simulator (RAMS) for Europe only (i.e. it may be weighted towards short haul flights and it also appears to allow for a reorganization of the air traffic management structure). They concede that their simulations produced variable outputs depending on the parameters, including a 7.2% increase under some circumstances. 3.9% is the weighted mean.
Note that the conclusions do not advocate that such a reorganisation of air traffic should be undertaken, just that the results are interesting:
'The results presented here indicate that a strategy to avoid the production of contrails by restricting cruise altitude could provide a net benefit to climate, despite the associated increase in CO2 emission. The analysis suggests that the implications for controller workload present the most likely operational obstacles to such a scheme and that reconfiguration of airspace would be required to mitigate the impacts.'
The study of the effects on surface temperature of Sept 11th is this one:
Nature Volume 418(6898) 8 August 2002 p 601
Climatology: Contrails reduce daily temperature range
Travis, David J.*; Carleton, Andrew M.†; Lauritsen, Ryan G.*
Again, I have a copy.
They conclude:
'Our findings indicate that the diurnal temperature range averaged across the United States was increased during the aircraft-grounding period, despite large variations in the amount of cloud associated with mobile weather systems (Fig. 2). We argue that the absence of contrails was responsible for the difference between a period of above-normal but unremarkable DTR and the anomalous conditions that were recorded.'
In other words, there was clear evidence that contrails affect short term surface temperatures. No conclusions were drawn about the impact on global warming, but it does not seem unreasonable to hypothesise that the contrails have some role to play, be it positive or negative in terms of anthropogenic heating.
With regard to the science, the Intergovernmental Panel on Climate Change (IPCC) studied the role of aviation in global warming in detail (and continue to do so). Their detailed report is here:
http://www.grida.no/climate/ipcc/aviation/index.htm
With regards to contrails they said in the summary (there is more detail in the report)
( http://www.grida.no/climate/ipcc/aviation/007.htm#spm45 ):
4.5. Contrails
In 1992, aircraft line-shaped contrails are estimated to cover about 0.1% of the Earth’s surface on an annually averaged basis with larger regional values. Contrails tend to warm the Earth’s surface, similar to thin high clouds. The contrail cover is projected to grow to 0.5% by 2050 in the reference scenario (Fa1), at a rate which is faster than the rate of growth in aviation fuel consumption.
This faster growth in contrail cover is expected because air traffic will increase mainly in the upper troposphere where contrails form preferentially, and may also occur as a result of improvements in aircraft fuel efficiency...The radiative effect of contrails depends on their optical properties and global cover, both of which are uncertain. Contrails have been observed as line-shaped clouds by satellites over heavy air traffic areas and covered on average about 0.5% of the area over Central Europe in 1996 and 1997.
4.6. Cirrus Clouds
Extensive cirrus clouds have been observed to develop after the formation of persistent contrails. Increases in cirrus cloud cover (beyond those identified as line-shaped contrails) are found to be positively correlated with aircraft emissions in a limited number of studies. About 30% of the Earth is covered with cirrus cloud. On average an increase in cirrus cloud cover tends to warm the surface of the Earth. An estimate for aircraft-induced cirrus cover for the late 1990s ranges from 0 to 0.2% of the surface of the Earth. For the Fa1 scenario, this may possibly increase by a factor of 4 (0 to 0.8%) by 2050; however, the mechanisms associated with increases in cirrus cover are not well understood and need further investigation.
To say that these scientists do not know what they are talking about on the basis of third hand information would seem to be somewhat naive. Read their reports first-hand (all IPCC reports are available online for example), then make a decision.
This is a serious issue for aviation. The vast majority of climate scientists now accept that some anthropogenic global warming is occurring (IPCC involves about 1000 experts from universities, research centres, business and environmental associations, and other organizations in approximately 120 countries). As a result, the pressure to see reductions of change-causing processes is going to increase in the future. Aviation would be well-advised to act in a pre-emptive manner rather than have regulation imposed upon it. Burying our collective head in the sand is an unwise policy, whether you believe in the science or not.
Apologies for the long post
DrDave
Join Date: Sep 1999
Location: U.K
Posts: 68
Likes: 0
Received 0 Likes
on
0 Posts
This sort of nonsense is staggering in its naivety. It conveniently ignores the fact that any increase in fuel consumption, particularly on a long haul flight, may mean a reduction in payload to carry the extra fuel burnt. This payload would then have to be carried on another aircraft, burning yet more fuel and the domino effect would almost certainly mean a larger overall increase in CO2 emissions, surely outweighing any of the so called benefits from reflection of radiation by cirrus clouds.
Put any longhaul aircraft more than 4000 feet off its optimum altitude and the increase in burn is going to be closer to 10% than the 3.9% 'weighted mean'. Most 747s, 777s and 340s in ISA conditions are likely to be close to optimum cruise altitude at FL330 after a MTOW departure; they are also likely to get up to FL350 or metric equivalent within three hours of departure.
At lighter weights, on shorter (ex Europe to East Coast USA, Middle East, India, Pakistan etc.), they like to get to FLs above 370 straight away, therefore inflicting at least a 6000 foot deviation from the optimum.
Still, as we are in the U.K, according to experts, probably reaping the seeds of global warming, because we're actually having a summer, they must be right..................
Put any longhaul aircraft more than 4000 feet off its optimum altitude and the increase in burn is going to be closer to 10% than the 3.9% 'weighted mean'. Most 747s, 777s and 340s in ISA conditions are likely to be close to optimum cruise altitude at FL330 after a MTOW departure; they are also likely to get up to FL350 or metric equivalent within three hours of departure.
At lighter weights, on shorter (ex Europe to East Coast USA, Middle East, India, Pakistan etc.), they like to get to FLs above 370 straight away, therefore inflicting at least a 6000 foot deviation from the optimum.
Still, as we are in the U.K, according to experts, probably reaping the seeds of global warming, because we're actually having a summer, they must be right..................
Join Date: Aug 2003
Location: Skagness on the beach
Posts: 882
Likes: 0
Received 0 Likes
on
0 Posts
Just think of what lower and slower would do to ETOPs?? 
No more polar routes.
Even if you design and build an aircraft that is optimum at the lower altitudes it will be a generation or two before you see any benefit as there will be so many aircraft already in use that are not optimum at that altitude.
No more polar routes. Even if you design and build an aircraft that is optimum at the lower altitudes it will be a generation or two before you see any benefit as there will be so many aircraft already in use that are not optimum at that altitude.
Join Date: Aug 2000
Location: UK
Posts: 1,914
Likes: 0
Received 0 Likes
on
0 Posts
Dr. Dave and Thread Bear (sounds like childrens show characters), they are quite simply using faulty data to produce the result they want! <<They concede that their simulations produced variable outputs depending on the parameters, including a 7.2% increase under some circumstances. 3.9% is the weighted mean.>> If you are going to limit jets to 24000' maximum when they are designed to go at 35,000'+ for efficiency (and the B777 higher still), then it is going to cost a darn sight more than 3.9% or 7.2%! Trouble is, these people look up in the sky and see those contrails and think what a shame they appear to be screwing up the ecology (that is until they want to go somewhere hot and sunny when it's OK for the world to make the sacrifice). So they grab hold of faulty data to prove what they want.
Watch my (virtual) lips- they are wrong. They are using faulty data. Therefore the world will be using up vastly greater resources and producing more pollution to get the job done if these idiots start getting people to believe them! Me- I don't care. If I am made to go below 24,000, suits me- I'll be getting less radiation, flying everywhere lower and vastly slower and not getting so out of breath. But you know it is just a left wing/chemtrailer/Greenpeace creep conspiracy, don't you?
Watch my (virtual) lips- they are wrong. They are using faulty data. Therefore the world will be using up vastly greater resources and producing more pollution to get the job done if these idiots start getting people to believe them! Me- I don't care. If I am made to go below 24,000, suits me- I'll be getting less radiation, flying everywhere lower and vastly slower and not getting so out of breath. But you know it is just a left wing/chemtrailer/Greenpeace creep conspiracy, don't you?
Thread Starter
Join Date: Jul 2003
Location: No Fixed Address
Posts: 30
Likes: 0
Received 0 Likes
on
0 Posts
Thank you for sharing your opinions there Notso Fantastic. All kinds are welcome.
I posted this article to see the view of others on the matter. I am by no means a tree hugger or staunch greenie but I am INTERESTED.
Thanks Dr Dave for shedding more light on the topic, and the others that contributed.
T.B
I posted this article to see the view of others on the matter. I am by no means a tree hugger or staunch greenie but I am INTERESTED.
Thanks Dr Dave for shedding more light on the topic, and the others that contributed.
T.B
Join Date: Jul 2001
Location: New Zealand
Posts: 254
Likes: 0
Received 0 Likes
on
0 Posts
This discussion about greenhouse gases and global warming would appear to depend on faulty assumptions.
The basic source of heat on Earth is Solar radiation, and any upset of the Atmosphere and Stratosphere which results in an extended cloud cover will result in a reduction of Solar Radiation reaching Earth, and a consequent temperature REDUCTION, which is not what the Tree-huggers et al preach.
One only need study what happens in a desert with clear skies, where unimpeded solar radiation in daylight raises the temperatures to very high levels, whereas at night the reverse is true with the net outflow of long-wave radiation causing night time temperatures to plummet.
During World War II, Allied POW’s incarcerated in German POW Camps spent as much time as possible sun bathing to compensate for the reduced vitamin intake of the prison diets.
With the advent of the Allied daylight bombing offensive, huge flotillas of B-17 and B-24 aircraft of the USAAF caused massive contrails to form, and which rapidly spread to become a high overcast spreading from horizon to horizon.
The results were a marked drop in air temperature, and disgruntled prisoners, who missed out on sun bathing and were forced to don more clothing.
The basic source of heat on Earth is Solar radiation, and any upset of the Atmosphere and Stratosphere which results in an extended cloud cover will result in a reduction of Solar Radiation reaching Earth, and a consequent temperature REDUCTION, which is not what the Tree-huggers et al preach.
One only need study what happens in a desert with clear skies, where unimpeded solar radiation in daylight raises the temperatures to very high levels, whereas at night the reverse is true with the net outflow of long-wave radiation causing night time temperatures to plummet.
During World War II, Allied POW’s incarcerated in German POW Camps spent as much time as possible sun bathing to compensate for the reduced vitamin intake of the prison diets.
With the advent of the Allied daylight bombing offensive, huge flotillas of B-17 and B-24 aircraft of the USAAF caused massive contrails to form, and which rapidly spread to become a high overcast spreading from horizon to horizon.
The results were a marked drop in air temperature, and disgruntled prisoners, who missed out on sun bathing and were forced to don more clothing.
Guest
Posts: n/a
HectorusRex
I'm afraid your post is over-simplifying a very complex system.
The key to increased temperatures due to changes in atmospheric composition comes from the relative transparency of the atmosphere to various types of radiation.
The Earth receives energy from the sun in the form of shortwave radiation. It re-emits it in the form of long wave radiation. For constant temperature the amount coming in must equal the amount going out.
This is basically illustrated in the following diagram
(http://www.yale.edu/ceo/images/GuideFig1.gif):
A the top, the curve on the left is the spectrum for incoming radiation, the one on the right for outgoing.
At the bottom, the wavelengths of radiation absorped by different atmospheric gases are shown. So on the far left (short wavelength) is ozone, which absorbs high energy radiation, protecting the surface.
Note that H20 appears several times, as does CO2 etc. So changing the concentrations of these gases changes the amount of energy being absorped in different parts of the spectrum.
Overall effect is that changing atmospheric chemistry probably changes the balance between incoming and outgoing radiation, and thus changes global climate.
Unfortunately CO2 and water vapour are more effeicient at trapping long wave than short wave radiation, so increasing their concentration in the atmosphere will lead to more radiation being retained than is being emitted. The effect of this is increased temperature.
The smoking gun, to coin a phrase, is the Vostok ice core, from which it was possible to determine global temperature over the last 150,000 years and, by extracting gas bubbles, to measure the atmospheric chemistry.
The two curves are plotted here (sorry can't find a way to link this):
http://www.geocraft.com/WVFossils/temp_vs_CO2.html
Given the correlation between these curves can you really argue that levels of CO2 are not linked to temperature?
By the way this core was drilled and analysed by Russian scientists before the end of Communism. Notsofantastic, I bet you didn't realise your conspiracy was so far reaching?
DrDave (rather relishing being a children's show character!)
I'm afraid your post is over-simplifying a very complex system.
The key to increased temperatures due to changes in atmospheric composition comes from the relative transparency of the atmosphere to various types of radiation.
The Earth receives energy from the sun in the form of shortwave radiation. It re-emits it in the form of long wave radiation. For constant temperature the amount coming in must equal the amount going out.
This is basically illustrated in the following diagram
(http://www.yale.edu/ceo/images/GuideFig1.gif):
A the top, the curve on the left is the spectrum for incoming radiation, the one on the right for outgoing.
At the bottom, the wavelengths of radiation absorped by different atmospheric gases are shown. So on the far left (short wavelength) is ozone, which absorbs high energy radiation, protecting the surface.
Note that H20 appears several times, as does CO2 etc. So changing the concentrations of these gases changes the amount of energy being absorped in different parts of the spectrum.
Overall effect is that changing atmospheric chemistry probably changes the balance between incoming and outgoing radiation, and thus changes global climate.
Unfortunately CO2 and water vapour are more effeicient at trapping long wave than short wave radiation, so increasing their concentration in the atmosphere will lead to more radiation being retained than is being emitted. The effect of this is increased temperature.
The smoking gun, to coin a phrase, is the Vostok ice core, from which it was possible to determine global temperature over the last 150,000 years and, by extracting gas bubbles, to measure the atmospheric chemistry.
The two curves are plotted here (sorry can't find a way to link this):
http://www.geocraft.com/WVFossils/temp_vs_CO2.html
Given the correlation between these curves can you really argue that levels of CO2 are not linked to temperature?
By the way this core was drilled and analysed by Russian scientists before the end of Communism. Notsofantastic, I bet you didn't realise your conspiracy was so far reaching?
DrDave (rather relishing being a children's show character!)
Join Date: Aug 2000
Location: UK
Posts: 1,914
Likes: 0
Received 0 Likes
on
0 Posts
Dr.....most interesting. But may I say a little simplistic? <<The Earth receives energy from the sun in the form of shortwave radiation. It re-emits it in the form of long wave radiation. For constant temperature the amount coming in must equal the amount going out.>>....this is quite ignoring the heat energy within the earth, and how much is leaking to the surface. We all know it's pretty hot down there. The thing is, the earth is not constant, Ice Ages come and go, everything cycles. As I see it, all the alleged pollution mankind produces is but a mere trifle compared to a resounding 'burp' from a damn good volcano- the sort of volcano Mamma used to make- a Mt. St. Helens or Pinatubo or Montserrat. If the world is global warming, it's doing it anyway- we really are not that influential. I'm told simultaneously I am causing global warming for which I will get zapped with a new Ice Age, and yes- I'll get stuffed when the Poles change around and then where will my compasses be? I hope I will be in Cyprus enjoying a bit of global warming for the next 50 years!
I have gone from being a member of Friends of the Earth and Greenpeace to totally regarding such organisations as 'political' and cynically against anything to do with 'progress'. We are not going to save the Earth by preventing a motorway being built- forcing people out of cars onto disgusting UK public transport will achieve nothing (they will pay whatever it takes to avoid such a fate). Concorde harms nothing.
I have gone from being a member of Friends of the Earth and Greenpeace to totally regarding such organisations as 'political' and cynically against anything to do with 'progress'. We are not going to save the Earth by preventing a motorway being built- forcing people out of cars onto disgusting UK public transport will achieve nothing (they will pay whatever it takes to avoid such a fate). Concorde harms nothing.
Guest
Posts: n/a
Notso fantastic
Again, you raise some interesting points.
Addressing your points in turn:
>This is quite ignoring the heat energy within the earth, and how
>much is leaking to the surface.
Fair point, but it is easy to show that the amount of energy transfered to the surface from geothermal heat is trivial in comparison with the amount of energy coming in from the sun. Proof of this can be seen on the Antarctic continent, which has ice frozen to the bedrock across most of the land surface. If geothermal heat was so significant it would melt the bed.
>We all know it's pretty hot down there. The thing is, the earth is
> not constant, Ice Ages come and go, everything cycles.
True, ice ages are controlled by the Milankovic Cycles, which are associated with changes in the orbital characteristics of the Earth. The next Ice Age will come, pretty much regardless of what humans do, though we may delay it a little. But these changes occur on 100,000 year cycles (the last glacial maximum was c. 20,000 years ago, the last interglacial c. 100,000 years ago). The change we are seeing occurs on a much shorter timescale, and is occurring MUCH faster than any other change we can find in the geological record, except the extinction events (which is a warning in itself).
> As I see it, all the alleged pollution mankind produces is but a
> mere trifle compared to a resounding 'burp' from a damn good
> volcano
Yes, volcanoes have a big influence. But their impacts are a short burp, followed by a long period without burps. What we are doing is releasing a constant stream.
Taking CO2 for example, annual anthropogenic emissions are thought to be more than 150x the annualised emissions from volcanic sources (Gerlach 1991 if you want to know the source of this)
Taking sulphur, volcanic and other natural sources = 25 Tg / year. Human sources = 79 Tg (i.e 3x as much) (source = Andres and Kasgnoc 1997)
We can show that a big volcanic eruption does change climate (no-one denies this). If we are putting so much more into the atmosphere, isn't it logical that this will affect climate too?
> I have gone from being a member of Friends of the Earth and
> Greenpeace to totally regarding such organisations as 'political'
> and cynically against anything to do with 'progress'.
I can't argue with that! Doesn't change the reality of the science though.
DrDave
Again, you raise some interesting points.
Addressing your points in turn:
>This is quite ignoring the heat energy within the earth, and how
>much is leaking to the surface.
Fair point, but it is easy to show that the amount of energy transfered to the surface from geothermal heat is trivial in comparison with the amount of energy coming in from the sun. Proof of this can be seen on the Antarctic continent, which has ice frozen to the bedrock across most of the land surface. If geothermal heat was so significant it would melt the bed.
>We all know it's pretty hot down there. The thing is, the earth is
> not constant, Ice Ages come and go, everything cycles.
True, ice ages are controlled by the Milankovic Cycles, which are associated with changes in the orbital characteristics of the Earth. The next Ice Age will come, pretty much regardless of what humans do, though we may delay it a little. But these changes occur on 100,000 year cycles (the last glacial maximum was c. 20,000 years ago, the last interglacial c. 100,000 years ago). The change we are seeing occurs on a much shorter timescale, and is occurring MUCH faster than any other change we can find in the geological record, except the extinction events (which is a warning in itself).
> As I see it, all the alleged pollution mankind produces is but a
> mere trifle compared to a resounding 'burp' from a damn good
> volcano
Yes, volcanoes have a big influence. But their impacts are a short burp, followed by a long period without burps. What we are doing is releasing a constant stream.
Taking CO2 for example, annual anthropogenic emissions are thought to be more than 150x the annualised emissions from volcanic sources (Gerlach 1991 if you want to know the source of this)
Taking sulphur, volcanic and other natural sources = 25 Tg / year. Human sources = 79 Tg (i.e 3x as much) (source = Andres and Kasgnoc 1997)
We can show that a big volcanic eruption does change climate (no-one denies this). If we are putting so much more into the atmosphere, isn't it logical that this will affect climate too?
> I have gone from being a member of Friends of the Earth and
> Greenpeace to totally regarding such organisations as 'political'
> and cynically against anything to do with 'progress'.
I can't argue with that! Doesn't change the reality of the science though.
DrDave
Join Date: Jun 2003
Location: London
Posts: 8
Likes: 0
Received 0 Likes
on
0 Posts
Just to add to DrDave above,
The presence of CO2 (and many other "greenhouse" gases) in the atmosphere is natural - because of the presence of these gases (the physical properties of which DrDave described), the effective temperature of the earth is greater than it might otherwise be - hence life is sustained. The issue at stake within the climate change debate is increases in concentrations of these greenhouse gases above background levels. Consequently, especially with regard to the role of Milankovitch forcing on 100, 41 an 20kyr timescales, any climate change signal will be small, and nested within much greater variability through time.
Hence regarding 'circumstantial' evidence of climate change, then it is necessary to regard it with a degree of caution. For example, shrinking Alpine glaciers are often cited as evidence for climate change, but this ignores more immediate and identifiable explanations, such as adjustment of ice masses from little ice age maxima, or the role or regional variability of climate
The presence of CO2 (and many other "greenhouse" gases) in the atmosphere is natural - because of the presence of these gases (the physical properties of which DrDave described), the effective temperature of the earth is greater than it might otherwise be - hence life is sustained. The issue at stake within the climate change debate is increases in concentrations of these greenhouse gases above background levels. Consequently, especially with regard to the role of Milankovitch forcing on 100, 41 an 20kyr timescales, any climate change signal will be small, and nested within much greater variability through time.
Hence regarding 'circumstantial' evidence of climate change, then it is necessary to regard it with a degree of caution. For example, shrinking Alpine glaciers are often cited as evidence for climate change, but this ignores more immediate and identifiable explanations, such as adjustment of ice masses from little ice age maxima, or the role or regional variability of climate
Join Date: Aug 2000
Location: UK
Posts: 1,914
Likes: 0
Received 0 Likes
on
0 Posts
Who knows how much internal energy is released by volcanism? Although Antarctica may be frozen solid, I read they are just discovering massive thermal vents in the Indian Ocean. Anyone guess how much heat is released into the oceans to eventually find its way upwards? Add on surface volcanos and hotspots, and it will dwarf the energy we coax out of atoms and coal and gasoline.
We are facing numerous extinction possibilities:
Volcanos and Deccan Traps
Meteors
Diseases
English Cricket team
Maybe I'm getting cynical, but I just can't lie awake at night worrying about all those 500 year McDonalds containers, or the people using faulty scientific logic to just plain make life harder for the rest of us!
As a matter of interest, I am flying a 747 to JFK tonight. I shall ask our flight planners to produce a flight plan restricted to 24,000' to compare. Of course, not everyone would get 24,000'. Based on current experience, we would have loads of flights restricted to 18,000' or below (with the whole world crowding into 24,000')! Hopefully an answer Sunday.
We are facing numerous extinction possibilities:
Volcanos and Deccan Traps
Meteors
Diseases
English Cricket team
Maybe I'm getting cynical, but I just can't lie awake at night worrying about all those 500 year McDonalds containers, or the people using faulty scientific logic to just plain make life harder for the rest of us!
As a matter of interest, I am flying a 747 to JFK tonight. I shall ask our flight planners to produce a flight plan restricted to 24,000' to compare. Of course, not everyone would get 24,000'. Based on current experience, we would have loads of flights restricted to 18,000' or below (with the whole world crowding into 24,000')! Hopefully an answer Sunday.
Guest
Posts: n/a
Notsofantastic
Actually it is quite simple to measure the geothermal gradient and energy balance. For example there have been numerous deep boreholes drilled into the Earth's crust, both in the oceans and onland, and measurement of the geothermal gradient occurs routinely.
In addition, there has been very extensive measurement of ocean temperature such that the global ocean heat flux is now well constrained.
Finally, deep earth geophysics tells us how much radioactive material there is down there in the core, so it is quite easy to calculate how much heat is being released.
There are various other ways too - trust me, it's covered (I can send you scientific articles to this end if you wish)
All of this suggests that the amount of energy being released is trivial compared with the solar flux. Of course it is much greater than that being released by humans - but it is not our release of heat that is the problem - it is the release of gases that then cause trapping of energy. An analogy would be old fashioned airliners with manual controls - when you move the joystick it is not the energy input that you put into the system that actually turns the aircraft, it is the effects of that input in terms of deflecting the ailerons that turns the aircraft. Same with global warming - it is not our heat output (which is trivial) but the by-products - gases - that are causing change.
Yes, we do face numerous extinction possibilities (not sure what you mean by Deccan traps though - the Deccan Traps are a volcanic area of India that erupted 60-65 million years ago, now essentially inactive), but all are very low probability. Global warming is on a different probability level, although to say that it is likely to cause human extinction is really scare-mongering.
I still think you are missing the point of the article (see my original posting). The article considered European airspace over a small area - i.e. lot's of short trips at relatively low altitude. It did not consider transatlantic service, which would yield very different results. Of course if you compare a single long haul trip (i.e. your trip today) at high altitude you will get very different results. I will be very interested to see how different though?
Finally, I should reiterate that this was a scientific paper exploring possible scenarios. The authors did not advocate that airspace changes like this should be undertaken, just opened up the debate about possible measures that could be employed. Science advances through hypothesis setting and validating / rejection. That is rather different from stating that this is the measure that should be employed. I agree though that the New Scientist interpretation was unhelpful.
Notsofantastic - if you would be interested in exploring whether we could put together a scientifically-valid argument, perhaps using the sort of data to which you allude, against the contents of the paper then please contact me directly. I would be very happy to help you do this (research is my expertise).
DrDave
Actually it is quite simple to measure the geothermal gradient and energy balance. For example there have been numerous deep boreholes drilled into the Earth's crust, both in the oceans and onland, and measurement of the geothermal gradient occurs routinely.
In addition, there has been very extensive measurement of ocean temperature such that the global ocean heat flux is now well constrained.
Finally, deep earth geophysics tells us how much radioactive material there is down there in the core, so it is quite easy to calculate how much heat is being released.
There are various other ways too - trust me, it's covered (I can send you scientific articles to this end if you wish)
All of this suggests that the amount of energy being released is trivial compared with the solar flux. Of course it is much greater than that being released by humans - but it is not our release of heat that is the problem - it is the release of gases that then cause trapping of energy. An analogy would be old fashioned airliners with manual controls - when you move the joystick it is not the energy input that you put into the system that actually turns the aircraft, it is the effects of that input in terms of deflecting the ailerons that turns the aircraft. Same with global warming - it is not our heat output (which is trivial) but the by-products - gases - that are causing change.
Yes, we do face numerous extinction possibilities (not sure what you mean by Deccan traps though - the Deccan Traps are a volcanic area of India that erupted 60-65 million years ago, now essentially inactive), but all are very low probability. Global warming is on a different probability level, although to say that it is likely to cause human extinction is really scare-mongering.
I still think you are missing the point of the article (see my original posting). The article considered European airspace over a small area - i.e. lot's of short trips at relatively low altitude. It did not consider transatlantic service, which would yield very different results. Of course if you compare a single long haul trip (i.e. your trip today) at high altitude you will get very different results. I will be very interested to see how different though?
Finally, I should reiterate that this was a scientific paper exploring possible scenarios. The authors did not advocate that airspace changes like this should be undertaken, just opened up the debate about possible measures that could be employed. Science advances through hypothesis setting and validating / rejection. That is rather different from stating that this is the measure that should be employed. I agree though that the New Scientist interpretation was unhelpful.
Notsofantastic - if you would be interested in exploring whether we could put together a scientifically-valid argument, perhaps using the sort of data to which you allude, against the contents of the paper then please contact me directly. I would be very happy to help you do this (research is my expertise).
DrDave
Ecce Homo! Loquitur...
I fear someone is being disingenuous,
The text of the original article did not state it was limiting itself to discussing short haul flights. On the contrary, it went out of it's way to say that, "But global air traffic is growing by around 3.5 per cent per year, and many of those extra flights are long-haul, high-altitude, contrail-forming journeys."
The figures are stated as being a simulation of that over the busiest part of Europe, taken together with the comment above, it is an obvious attempt to imply that it represents the future level of global long haul traffic.
I believe the point being made is valid. This was either badly written, with the comment about long haul traffic being an irrelevant aside, more probably it was introduced intentionally, even though unsupported by the data.
The text of the original article did not state it was limiting itself to discussing short haul flights. On the contrary, it went out of it's way to say that, "But global air traffic is growing by around 3.5 per cent per year, and many of those extra flights are long-haul, high-altitude, contrail-forming journeys."
The figures are stated as being a simulation of that over the busiest part of Europe, taken together with the comment above, it is an obvious attempt to imply that it represents the future level of global long haul traffic.
I believe the point being made is valid. This was either badly written, with the comment about long haul traffic being an irrelevant aside, more probably it was introduced intentionally, even though unsupported by the data.
Last edited by ORAC; 8th Aug 2003 at 02:06.
Join Date: Jan 2001
Location: Location, Location
Posts: 642
Likes: 0
Received 0 Likes
on
0 Posts
A very interesting thread. A couple of observations which I'd be grateful for Dr Dave (or anyone else) to comment upon:
(a) There is incontrovertible evidence that global CO2 levels have increased substantially over the last 150 years (and are continuing to increase, although the rate is slowing). The evidence that this change has resulted in global temperature increases over the same period is much thinner.
(b) Models of the earth's climate are still pretty crude. One of the biggest problems is lack of computing power which forces the use of very coarse grids (around 1km square) which can take no account of smaller-scale phenomena such as clouds. Another problem is our lack of understanding of how the climate actually works! Estimates of future global warming amount (IMHO) to little more than a best guess.
(a) There is incontrovertible evidence that global CO2 levels have increased substantially over the last 150 years (and are continuing to increase, although the rate is slowing). The evidence that this change has resulted in global temperature increases over the same period is much thinner.
(b) Models of the earth's climate are still pretty crude. One of the biggest problems is lack of computing power which forces the use of very coarse grids (around 1km square) which can take no account of smaller-scale phenomena such as clouds. Another problem is our lack of understanding of how the climate actually works! Estimates of future global warming amount (IMHO) to little more than a best guess.
Join Date: Dec 2001
Location: europe
Posts: 546
Likes: 0
Received 0 Likes
on
0 Posts
Dr Dave's graphs, the linked ones that is, do indeed show a possible link between CO2/T in the fluctuations over 250,000 years.
However what is missing are graphs over the same period linking CO2/T/Airliners/human activity.
The graphs do not of course explain conclusively whether CO2 increases are caused by increased T, through the effect on lifeforms and the capacity of water to hold CO2, or whether the increase in CO2 from some source causes the increases in T.
As some have pointed out the sun's fluctuations, and our varying distance from the sun , are the prime source for climate change, and in its own small way this European summer, linking with a recent double top in solar activity, and the recent increase in the same in June/July tend to back up this proposition.
That said, contrails and aircraft high altitude emissions, which may not get recycled into the lower atmosphere, should be studied.
Afterall, human activity did cause London smog and cholera outbreaks. Not Linked though, except as human activity.
However what is missing are graphs over the same period linking CO2/T/Airliners/human activity.
The graphs do not of course explain conclusively whether CO2 increases are caused by increased T, through the effect on lifeforms and the capacity of water to hold CO2, or whether the increase in CO2 from some source causes the increases in T.
As some have pointed out the sun's fluctuations, and our varying distance from the sun , are the prime source for climate change, and in its own small way this European summer, linking with a recent double top in solar activity, and the recent increase in the same in June/July tend to back up this proposition.
That said, contrails and aircraft high altitude emissions, which may not get recycled into the lower atmosphere, should be studied.
Afterall, human activity did cause London smog and cholera outbreaks. Not Linked though, except as human activity.
Last edited by bluskis; 8th Aug 2003 at 02:23.