And lower down in the heavens . . .. . . . . .. . . . savings to be made.
Small altitude changes could cut contrail impact of flights by up to 59 per cent
Previous research suggests that contrails and the clouds they help form have as much of a warming impact on the climate as aviation’s cumulative CO2 emissions, because of an effect known as ‘radiative forcing’.
Radiative forcing is not at all specific to that phenomenon. It refers to the sum of additional thermal energies which exceed the nominal levels because of infusion of greenhouse gases in atmosphere. Surely, clouds and contrails contribute. But because warmer atmosphere holds more water vapor, the water contributes, too, and a lot: It roughly doubles the effect of all the other greenhouse gases.
However, radiative forcing only indirectly participates in global warming. The latter happens because top-of-atmosphere is higher in a greenhouse gas-laden atmosphere than one with less. The lapse rate gives a profile of how temperature increases with altitude, all the way to top-of-atmosphere. It monotonically decreases, on average and globally. If top-of-atmosphere gets higher, working backwards along that curve means surface temperature must be higher. Therefore, global warming.
That’s way above my thick head (I’m afraid), but I’ll pass your comment along to (Caroline Brogan) the author of article at the Imperial College London, as I’m sure they want there releases to be accurate and not viewed as “Fake News”.
Short answer, no. One of the companies cited as working on ‘clean ‘ rockets claims ‘The use of a renewable, bio-propane fuel that cuts carbon emissions by 90% compared to old-fashioned hydrocarbons’. Burning ‘bio-propane’ has exactly the same emissions as burning propane, plus the CO2 from the energy used to produce it. The CO2 released has the same effect as all those cars, and the water vapour from the hydrogen is largely emitted above the tropopause, where it’s much worse than at ground level. https://spacenews.com/op-ed-time-to-clear-the-air-about-launch-pollution/
Biofuels are called biofuels because their carbon content comes from CO2 *already* in the atmosphere and which was scrubbed from the atmosphere by biological agents. Net increase to atmosphere CO2 = zero.
Propane is carbon molecules previously *sequestered* underground, therefore not part of the carbon cycle. Net increase to atmosphere CO2 = 100%.
Yes, Virgin, for one, is pushing the limits on using biofuels in their aircraft to achieve the benefits GB cites. There’s a tradeoff though: Biofuels for aircraft don’t have the same “umph” as direct petroleum, so a bit more is needed for same mileage, so more emissions, and more weight to carry
Parrying in anticipation another comment I’ve gotten is that biofuels are GM heavy and, so, bad. I took the opportunity to research, and I’ve concluded the popular notions about GM are bupkis.
Grant that biofuels have effectively no Carbon emissions because of how they are obtained. Granted, that’s probably not entirely true, given the upstream emissions for any product, e.g., planting/harvesting, transport, processing, etc, but those will go to zero as the economic decarbonizes. That’s why criticizing EVs because of the fossil fuels used to generate the electricity which charges them is misguided: It’s not the EV owners responsibility for completely foolish practices on the part of their local utility and, probably, the state where the utility is located.
Unfortunately, the thrust per unit of biofuel kerosene (or whatever the jet fuel is) is 0.95 that of the same unit of petroleum kerosene by unit mass. (As I said, I’m making that up, and don’t have time at the moment to check on what the actual number is.) So that means if biofuel is burned for a fixed time, to get the thrust integrated over that time about 5% more biofuel (actually 1/.95) is needed than the corresponding amount of petroleum kerosene.
Now suppose per unit thrust petroleum kerosene emits E units of greenhouse gases (setting aside water vapor for a moment). Accordingly, the amount of emissions saved isn’t E, it’s E/(1/.95) or 0.95E if 0.95 is that thrust factor. BUT, because 5% more biofuel is needed, that means, assuming the masses of biofuel kerosene and petro kerosene are identical it also means 5% more biofuel needs to be carried. That means the engines need to work a bit harder, so it means actually the range on a unit of biofuel isn’t just 0.95 that of petro, it’s less, maybe 0.9. Accordingly only 0.9E is offset.
Then, as in the case of Virgin, they have found, for whatever reasons, that they can’t use more than a 30% biofuel mix, even if their engines are tweaked to be able to use more biofuel. (I don’t know enough about jet engines to understand what the limits there are.) So, really, because biofuel is at best 30%, you still need the 7-parts-in-10 petro to fly, so using biofuel doesn’t save you 0.9E, it’s more like only E/4 is saved so 3E/4 is still emitted.
I don’t know how much, if any, difference there is between the water vapor emitted from biofuel kerosene combustion versus petroleum kerosene. If it’s the same, then both contribute to injecting water vapor where it does not belong — in stratosphere, where natural water vapor doesn’t reach because it condenses out — and so both contribute to those effects. These can be more or less than simple contrail formation. Recall, water vapor is a pretty potent greenhouse gas, but its absorption spectra are off the main lobe of IR emissions from the surface.
So, at least right now, this is a win, but it doesn’t replace the emissions.
Don’t know about rockets. Hydrogen is a clear win (upper stages of Boeing’s Atlas have those), but Hydrogen is nasty stuff to use as rocket fuel … The tanks either have to be extra sturdy or you have to accept that the H2 will leak out through the metal and also make its surface so cold ice will form on top of it loading the rocket. Also, the loading might not be symmetric and so you can get imbalances and asymmetric wind shear, etc.
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“Accordingly only 0.9E is offset.”
Huh?
No fossil fuel was used – so it is all offset. That a slightly larger volume of fuel was used is, as far as I can see, irrelevant.
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Maybe irrelevant to you but if y’need to burn more non-biofuel to go slightly farther …. But whatever.
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Biofuels don’t come from carbon in the atmosphere, they come from carbon in plants, are burnt, and then go to CO2 in the atmosphere. The biofuels can come from crops or trees grown specifically for the purpose, or from ‘waste’ from food or timber. In either case, they’re taking carbon which would have stayed solid, at least for a while, and turning it into a gas. The best way for trees to sequester carbon is to just keep on being trees, not to burn them then start over. We should be trying to reduce cropland, and letting the remainder go back to nature, not increasing areas for biofuels with minimal advantages, if any, over fossils. The US and Britain ran on biofuels in the 1700s, and as a result, there was hardly a tree left standing over huge areas. Forests in the eastern US only recovered with the widespread use of coal and oil instead. Now, with populations an order of magnitude larger, and energy use per person far higher, relying on biofuels for even a fraction of our needs would leave very little for the natural world to regenerate.
Ah yes, biofuels—yet another BS “solution” in many cases. Check out the Dogwood Alliance website for info on how the greedy corporations are chopping down forests in the SE US, turning them into wood pellets, and shipping them to the UK to be burned as a “renewable” fuel. It’s enough to gag you.
Her’s GB, with another of his irrelevant straw men rather than a real argument.
And many biofuels, like wood pellets, are NOT really green (except for the color of the money their promoters hope to make from them.
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This is an old article, but it’s still true, and still going on -https://www.monbiot.com/2005/12/06/worse-than-fossil-fuel/
Corn ethanol is nearly as bad -https://www.newscientist.com/article/dn12283-corn-biofuel-dangerously-oversold-as-green-energy/
Using trees instead of coal likewise -https://www.theguardian.com/environment/2019/dec/16/converting-coal-plants-to-biomass-could-fuel-climate-crisis
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Wood is not a biofuel.
Biofuels are liquids or gases.
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Wood is not a biofuel? WHAT? (Omno apparently lives on in GB) A quick search finds:
“In fact, a biofuels can be any renewable, biological material used as fuel. With that definition, it becomes clear that things like wood, sawdust, leaves, and even dried animal dung all constitute biofuels”.
“Wood constitutes the majority of biomass that is burned for fuel and comes in the forms firewood, charcoal, chips, pellets, and sawdust. The use of wood as a fuel for cooking, heating, and other applications dates back to well before humans when Neanderthals were the predominant species of hominid. In fact, the most troubling aspect of using wood as a fuel is generating the spark to start the fire. Otherwise, wood is readily available, abundant, and can even be collected from the ground if cutting tools are not available. Today, wood is even used in some electric generating applications”.
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“Globally averaged, present-day rocket particle accumulations cool the troposphere by about 0.02 watt per square meter [Ross and Sheaffer, 2014], whereas carbon dioxide emissions from global aviation warm the troposphere by about 0.03 watt per square meter [Lee et al., 2009]. Although these two effects involve different physics, the comparison nevertheless provides a useful context for understanding the relative magnitude of the climate impact of rocket launches. The magnitude of present-day cooling from rocket particles is about the same as the magnitude of warming from aviation carbon dioxide. In other words, rocket launches cool Earth’s surface by about the same amount that aviation warms it.
It would be an overinterpretation to conclude that rocket cooling mitigates some greenhouse gas (GHG) warming. Research shows that Earth responds to stratospheric particle injections in complex ways, with some atmospheric regions becoming warmer and others cooler, on subglobal and subseasonal scales [Kravitz et al., 2012]. Similarly, Earth will respond to rocket particle injections in complex ways. Unraveling this complexity and accurately assessing the potential effects of the coming surge in rocket emissions require sophisticated computer modeling efforts. Such efforts have yet to be realized.”
It sure would be nice if people knew how to perform a sim-Le google search before spouting of, I doesn’t take a rocket scientist, oops I am a rocket scientist. Go figure:
“2) CO2 is often cited as the ‘most important manmade greenhouse gas.’ Even so, rockets don’t contribute much to the background CO2, which is
already quite large due to natural and man-made emissions. It is very likely that unless rocket activities increase by many orders of magnitude, CO2
emissions will not contribute to any changes in climate that can be directly attributed to ‘rockets.’ However, it is important to note that CO2 emitted
by rockets will have the same affect on Earth’s temperatures as CO2 emitted at the surface (to first order). This is because the CO2 molecules in
both cases spend about the same amount of time in the atmosphere, eventually becoming indistinguishable from each other. “
Is part of the effect that, well, the point of (most) rocketry is to punch through troposphere and stratosphere, not wanting to spend a lot of time there?
You would think so, what they are saying is essentially all C02 is the same and that C02 signature from rockets is more or less negligible currently when compared to all other forms of GHG emissions. I found the statement about being 200yr worth of one automobile to be hyperbole that misleads and distorts the truth. Of course it is true that rocket launches are on the increase, so green propulsion should be ramped up ASAP.
Addition to my question … Except, of course, when the modus op includes recovery. Don’t get me wrong … I bet the upstream emissions saved by reusing launched infrastructure outweighs anything emitted in recovering them.
Time to stop all this self-aggrandizing mathematical eco-quacking and hear from the Luddites.
What’s “green” is minimizing or eliminating rocket launches and airplane flights—-we keep looking for technological fixes for things that should never have happened in the first place.
Forget going to the moon, forget going to Mars, forget space flight for the rich and self indulgent, forget tourists flying all over the world, forget sending up satellites so that people can get rich from them—-all of that is expected to grow in the future, and NONE of it will help save the planet.
To be honest you are right. Now if you have a time travel machine and the key to going back and stopping 400+ years of White Male genocide of Native Americans we might be on to something. But how much energy is that time machine going to need?
We have a lot more mistakes than genocide of Native Americans over the past 400 years that we should go back and “fix” if we had the means. Not to worry, about energy though—-we have plenty of COAL to burn and show little sign of eliminating it.
And lower down in the heavens . . .. . . . . .. . . . savings to be made.
Small altitude changes could cut contrail impact of flights by up to 59 per cent
Previous research suggests that contrails and the clouds they help form have as much of a warming impact on the climate as aviation’s cumulative CO2 emissions, because of an effect known as ‘radiative forcing’.
https://www.imperial.ac.uk/news/195294/small-altitude-changes-could-climate-impact/
@redskylite,
Radiative forcing is not at all specific to that phenomenon. It refers to the sum of additional thermal energies which exceed the nominal levels because of infusion of greenhouse gases in atmosphere. Surely, clouds and contrails contribute. But because warmer atmosphere holds more water vapor, the water contributes, too, and a lot: It roughly doubles the effect of all the other greenhouse gases.
However, radiative forcing only indirectly participates in global warming. The latter happens because top-of-atmosphere is higher in a greenhouse gas-laden atmosphere than one with less. The lapse rate gives a profile of how temperature increases with altitude, all the way to top-of-atmosphere. It monotonically decreases, on average and globally. If top-of-atmosphere gets higher, working backwards along that curve means surface temperature must be higher. Therefore, global warming.
That’s way above my thick head (I’m afraid), but I’ll pass your comment along to (Caroline Brogan) the author of article at the Imperial College London, as I’m sure they want there releases to be accurate and not viewed as “Fake News”.
Short answer, no. One of the companies cited as working on ‘clean ‘ rockets claims ‘The use of a renewable, bio-propane fuel that cuts carbon emissions by 90% compared to old-fashioned hydrocarbons’. Burning ‘bio-propane’ has exactly the same emissions as burning propane, plus the CO2 from the energy used to produce it. The CO2 released has the same effect as all those cars, and the water vapour from the hydrogen is largely emitted above the tropopause, where it’s much worse than at ground level.
https://spacenews.com/op-ed-time-to-clear-the-air-about-launch-pollution/
You are contesting the efficacy of all biofuels?
Biofuels are called biofuels because their carbon content comes from CO2 *already* in the atmosphere and which was scrubbed from the atmosphere by biological agents. Net increase to atmosphere CO2 = zero.
Propane is carbon molecules previously *sequestered* underground, therefore not part of the carbon cycle. Net increase to atmosphere CO2 = 100%.
Yes, Virgin, for one, is pushing the limits on using biofuels in their aircraft to achieve the benefits GB cites. There’s a tradeoff though: Biofuels for aircraft don’t have the same “umph” as direct petroleum, so a bit more is needed for same mileage, so more emissions, and more weight to carry
Parrying in anticipation another comment I’ve gotten is that biofuels are GM heavy and, so, bad. I took the opportunity to research, and I’ve concluded the popular notions about GM are bupkis.
“so a bit more is needed for same mileage, so more emissions, and more weight to carry”
So, more emissions that don’t count? What is the problem?
@GB,
I’m making up numbers here purely to illustrate.
Grant that biofuels have effectively no Carbon emissions because of how they are obtained. Granted, that’s probably not entirely true, given the upstream emissions for any product, e.g., planting/harvesting, transport, processing, etc, but those will go to zero as the economic decarbonizes. That’s why criticizing EVs because of the fossil fuels used to generate the electricity which charges them is misguided: It’s not the EV owners responsibility for completely foolish practices on the part of their local utility and, probably, the state where the utility is located.
Unfortunately, the thrust per unit of biofuel kerosene (or whatever the jet fuel is) is 0.95 that of the same unit of petroleum kerosene by unit mass. (As I said, I’m making that up, and don’t have time at the moment to check on what the actual number is.) So that means if biofuel is burned for a fixed time, to get the thrust integrated over that time about 5% more biofuel (actually 1/.95) is needed than the corresponding amount of petroleum kerosene.
Now suppose per unit thrust petroleum kerosene emits E units of greenhouse gases (setting aside water vapor for a moment). Accordingly, the amount of emissions saved isn’t E, it’s E/(1/.95) or 0.95E if 0.95 is that thrust factor. BUT, because 5% more biofuel is needed, that means, assuming the masses of biofuel kerosene and petro kerosene are identical it also means 5% more biofuel needs to be carried. That means the engines need to work a bit harder, so it means actually the range on a unit of biofuel isn’t just 0.95 that of petro, it’s less, maybe 0.9. Accordingly only 0.9E is offset.
Then, as in the case of Virgin, they have found, for whatever reasons, that they can’t use more than a 30% biofuel mix, even if their engines are tweaked to be able to use more biofuel. (I don’t know enough about jet engines to understand what the limits there are.) So, really, because biofuel is at best 30%, you still need the 7-parts-in-10 petro to fly, so using biofuel doesn’t save you 0.9E, it’s more like only E/4 is saved so 3E/4 is still emitted.
I don’t know how much, if any, difference there is between the water vapor emitted from biofuel kerosene combustion versus petroleum kerosene. If it’s the same, then both contribute to injecting water vapor where it does not belong — in stratosphere, where natural water vapor doesn’t reach because it condenses out — and so both contribute to those effects. These can be more or less than simple contrail formation. Recall, water vapor is a pretty potent greenhouse gas, but its absorption spectra are off the main lobe of IR emissions from the surface.
So, at least right now, this is a win, but it doesn’t replace the emissions.
Don’t know about rockets. Hydrogen is a clear win (upper stages of Boeing’s Atlas have those), but Hydrogen is nasty stuff to use as rocket fuel … The tanks either have to be extra sturdy or you have to accept that the H2 will leak out through the metal and also make its surface so cold ice will form on top of it loading the rocket. Also, the loading might not be symmetric and so you can get imbalances and asymmetric wind shear, etc.
“Accordingly only 0.9E is offset.”
Huh?
No fossil fuel was used – so it is all offset. That a slightly larger volume of fuel was used is, as far as I can see, irrelevant.
Maybe irrelevant to you but if y’need to burn more non-biofuel to go slightly farther …. But whatever.
Biofuels don’t come from carbon in the atmosphere, they come from carbon in plants, are burnt, and then go to CO2 in the atmosphere. The biofuels can come from crops or trees grown specifically for the purpose, or from ‘waste’ from food or timber. In either case, they’re taking carbon which would have stayed solid, at least for a while, and turning it into a gas. The best way for trees to sequester carbon is to just keep on being trees, not to burn them then start over. We should be trying to reduce cropland, and letting the remainder go back to nature, not increasing areas for biofuels with minimal advantages, if any, over fossils. The US and Britain ran on biofuels in the 1700s, and as a result, there was hardly a tree left standing over huge areas. Forests in the eastern US only recovered with the widespread use of coal and oil instead. Now, with populations an order of magnitude larger, and energy use per person far higher, relying on biofuels for even a fraction of our needs would leave very little for the natural world to regenerate.
Ah yes, biofuels—yet another BS “solution” in many cases. Check out the Dogwood Alliance website for info on how the greedy corporations are chopping down forests in the SE US, turning them into wood pellets, and shipping them to the UK to be burned as a “renewable” fuel. It’s enough to gag you.
Oh, so they have wood-burning furnaces to power airplanes now? Who knew?
And almost all biofuels are NOT made from wood.
Her’s GB, with another of his irrelevant straw men rather than a real argument.
And many biofuels, like wood pellets, are NOT really green (except for the color of the money their promoters hope to make from them.
This is an old article, but it’s still true, and still going on -https://www.monbiot.com/2005/12/06/worse-than-fossil-fuel/
Corn ethanol is nearly as bad -https://www.newscientist.com/article/dn12283-corn-biofuel-dangerously-oversold-as-green-energy/
Using trees instead of coal likewise -https://www.theguardian.com/environment/2019/dec/16/converting-coal-plants-to-biomass-could-fuel-climate-crisis
Wood is not a biofuel.
Biofuels are liquids or gases.
Wood is not a biofuel? WHAT? (Omno apparently lives on in GB) A quick search finds:
“In fact, a biofuels can be any renewable, biological material used as fuel. With that definition, it becomes clear that things like wood, sawdust, leaves, and even dried animal dung all constitute biofuels”.
“Wood constitutes the majority of biomass that is burned for fuel and comes in the forms firewood, charcoal, chips, pellets, and sawdust. The use of wood as a fuel for cooking, heating, and other applications dates back to well before humans when Neanderthals were the predominant species of hominid. In fact, the most troubling aspect of using wood as a fuel is generating the spark to start the fire. Otherwise, wood is readily available, abundant, and can even be collected from the ground if cutting tools are not available. Today, wood is even used in some electric generating applications”.
“Globally averaged, present-day rocket particle accumulations cool the troposphere by about 0.02 watt per square meter [Ross and Sheaffer, 2014], whereas carbon dioxide emissions from global aviation warm the troposphere by about 0.03 watt per square meter [Lee et al., 2009]. Although these two effects involve different physics, the comparison nevertheless provides a useful context for understanding the relative magnitude of the climate impact of rocket launches. The magnitude of present-day cooling from rocket particles is about the same as the magnitude of warming from aviation carbon dioxide. In other words, rocket launches cool Earth’s surface by about the same amount that aviation warms it.
It would be an overinterpretation to conclude that rocket cooling mitigates some greenhouse gas (GHG) warming. Research shows that Earth responds to stratospheric particle injections in complex ways, with some atmospheric regions becoming warmer and others cooler, on subglobal and subseasonal scales [Kravitz et al., 2012]. Similarly, Earth will respond to rocket particle injections in complex ways. Unraveling this complexity and accurately assessing the potential effects of the coming surge in rocket emissions require sophisticated computer modeling efforts. Such efforts have yet to be realized.”
https://eos.org/features/the-coming-surge-of-rocket-emissions
@peterangelo,
Thanks, Peter. That’s a great link!
It sure would be nice if people knew how to perform a sim-Le google search before spouting of, I doesn’t take a rocket scientist, oops I am a rocket scientist. Go figure:
“2) CO2 is often cited as the ‘most important manmade greenhouse gas.’ Even so, rockets don’t contribute much to the background CO2, which is
already quite large due to natural and man-made emissions. It is very likely that unless rocket activities increase by many orders of magnitude, CO2
emissions will not contribute to any changes in climate that can be directly attributed to ‘rockets.’ However, it is important to note that CO2 emitted
by rockets will have the same affect on Earth’s temperatures as CO2 emitted at the surface (to first order). This is because the CO2 molecules in
both cases spend about the same amount of time in the atmosphere, eventually becoming indistinguishable from each other. “
http://atoc.colorado.edu/~toohey/basics.html
@peterangelo,
Is part of the effect that, well, the point of (most) rocketry is to punch through troposphere and stratosphere, not wanting to spend a lot of time there?
You would think so, what they are saying is essentially all C02 is the same and that C02 signature from rockets is more or less negligible currently when compared to all other forms of GHG emissions. I found the statement about being 200yr worth of one automobile to be hyperbole that misleads and distorts the truth. Of course it is true that rocket launches are on the increase, so green propulsion should be ramped up ASAP.
@peterangelo,
Addition to my question … Except, of course, when the modus op includes recovery. Don’t get me wrong … I bet the upstream emissions saved by reusing launched infrastructure outweighs anything emitted in recovering them.
I didn’t see this mentioned anywhere and it happen last year:
https://www.nasa.gov/mission_pages/tdm/green/overview.html
Time to stop all this self-aggrandizing mathematical eco-quacking and hear from the Luddites.
What’s “green” is minimizing or eliminating rocket launches and airplane flights—-we keep looking for technological fixes for things that should never have happened in the first place.
Forget going to the moon, forget going to Mars, forget space flight for the rich and self indulgent, forget tourists flying all over the world, forget sending up satellites so that people can get rich from them—-all of that is expected to grow in the future, and NONE of it will help save the planet.
To be honest you are right. Now if you have a time travel machine and the key to going back and stopping 400+ years of White Male genocide of Native Americans we might be on to something. But how much energy is that time machine going to need?
We have a lot more mistakes than genocide of Native Americans over the past 400 years that we should go back and “fix” if we had the means. Not to worry, about energy though—-we have plenty of COAL to burn and show little sign of eliminating it.
In the meantime many earth observing satellites are providing valuable information.
Note that I spoke of “minimizing”. IMO, the only rocket launches that ARE defensible are those that put earth-observing satellite in orbit.