£15m plan to get the "Queen of the Skies" flying again.

[Hyronymus]

Can I also point out that as wonderful as a hydrogen engine that only produces water as an exhaust is, up at 30000ft contrails (which are formed by water vapour) are currently a bit of a pollution problem...

Indeed, think of all the extra rain we would get .

Make them fly over Africa, it'll solve some issues with rain there.

[JamieLei]

Make them fly over Africa, it'll solve some issues with rain there.

Ah Eurocentrism at its best!

Can I also point out that as wonderful as a hydrogen engine that only produces water as an exhaust is, up at 30000ft contrails (which are formed by water vapour) are currently a bit of a pollution problem...

They're not actually a pollution problem - it's more that they act as an radiation absorbing layer, keeping solar radiation out and long-wave terrestrial radiation in, just like most other types of cloud. They might be aesthetic pollution, but I'd debate the degree to which contrails affect global energy budgets. After all, they're very thin and short lived. It's the addition of particles such as sulphuric acid to the atmosphere that has effects.

[Ameecher]

What you chatting about Lei? Acid rain has NEVER been a problem.

See what I wrote? Never.

Ever.

[JamieLei]

My bad. I thought it was a reference to the September 11th study of aircraft contrails on atmospheric albedo and radiation reflection.

[EXTspotter]

Its not the effect of the clouds produced (and the water within) that is the problem, it is as Jamie says, the O-H bond present in water is very good at absorbing terrestrial IR radiation and reflecting it back to earth - more than 30 times more damaging than the C=O bond in carbon dioxide (as seen as the strengthened? greenhouse effect). However the main problem with water is when it gets to very high in the atmosphere, it doesn't form into clouds and just stays up there like a lemon for a long time, adding to the absorption/reflection proportion of the global energy budget. As Jamie said contrails themselves aren't the problem.

[JamieLei]

Its not the effect of the clouds produced (and the water within) that is the problem, it is as Jamie says, the O-H bond present in water is very good at absorbing terrestrial IR radiation and reflecting it back to earth - more than 30 times more damaging than the C=O bond in carbon dioxide (as seen as the strengthened? greenhouse effect). However the main problem with water is when it gets to very high in the atmosphere, it doesn't form into clouds and just stays up there like a lemon for a long time, adding to the absorption/reflection proportion of the global energy budget. As Jamie said contrails themselves aren't the problem.

Indeed - the most important greenhouse gas by FAR is water vapour

The reason we worry so much about CO2 is that it comprises a minute proportion of the atmosphere, but since the industrial revolution, concentration has increased from 280ppm to 380ppm (compared to previous lows of 180ppm over the last 440,000 years). The level of water vapour isn't increasing, but CO2 is.

[APDAF]

There's a 800 year lag between the temperature going up and carbon dioxide going up so we are in a cool period but the carbon dioxide is still going up.

[Kogut]

There's a 800 year lag between the temperature going up and carbon dioxide going up so we are in a cool period but the carbon dioxide is still going up.

Ekkhm. It also may mean that increased quantify of CO2 is caused by higher temperature.

[JamieLei]

There's a 800 year lag between the temperature going up and carbon dioxide going up so we are in a cool period but the carbon dioxide is still going up.

Ekkhm. It also may mean that increased quantify of CO2 is caused by higher temperature.

Doubt it. Higher temperature means more photosynthesis. It also means more chemical weathering which results in carbonate weathering which results in removal of CO2 from the atmosphere (see Raymo and Ruddiman, 1992). And no, there isn't so much a lag. The CO2 record and the temperature record through delta-18 oxygen isotope records in both the EPICA (750,000 years) and the Vostok (420,000 years) ice cores correspond very well (see Petit et. al., 1999). True, there may be a lag. But it shouldn't detract from the need to reduce emissions.

I'm also quite drunk atm. So remember those references is quite a feat. See also Francis and Oppenheimer, 2004 and McCormick et al, 1995 for information about Volcanic forcing on climate change too.

[EXTspotter]

The earth has its own seemingly negative-feedback loop with relation to CO2 and temperatures. Simply put increased CO2 levels leads to increased temperatures. Increased temperatures lead to greater evaporation and hence precipitation. Precipitation itself in higher latitudes causes a reduction in air temperature, causing more precipiation. This can have two effects. If the precipiation falls as liquid it has a very low albedo, which means energy is absorbed, increasing air temperature and humidity. However if it falls as snow it has a very very high albedo, this leads to most energy being reflected and a further drop in air temperature. If after an entire year has passed and there is still significant snow on the ground, snow/ice accumulation occurs, leading to a positive feedback loop which is known as an ice age, where the glaciated area expands to cover a large area of the planet. Somehow - I am not exactly sure - over time this causes a reduction in CO2 levels back to the original level and temperatures increase.

I know something like this is true, this could be right or it could be the exact opposite, i.e. low CO2 leads to ice ages, infact I think this is more likely. Pah! My poor A-level brain has failed me once again. Jamie! Save meeeeeeeee!

[audigex]

None of it can be conclusively proven, but there's strong evidence for human effect.

Overall temperatures are rising, CO2 (and the other greenhouse gases we hate) levels show a definite correlation with it.

Other effects may or may not be there, and the increasing outputs of CO2 may be having no effect at all, or they may be the only issue: the same for the other possibilities (including some we may not know about)... the problem with climate is that it's a damned big system, it takes a long time for changes to propagate from cause to effect.

My personal thought is that the planet has experienced far more drastic changes in temperature and survived fine: we're not going to destroy the planet with climate change. What we might do, however, is increase the rate of change (ie we change how fast the climate is changing, rather than directly changing the temperatures ourselves, which would be more "easily" fixable) until it hits a point where natural evolution can no longer cope (animals, plants, people) and species start to die out.

Best case: nothing happens, the planet does this sometimes, we all adapt and life goes on
More likely cases: some number of species dying out, increased occurance of natural disasters
Worst case: we all die

I don't know all the science (if I did, I'd be a lot richer) - but then, nor does anyone else. The problem is that we don't know where on the Fine<->Doom scale we are, and where we'll end up - and we don't really have any way to predict it other than "wait and see". The simple thing for me though is that since we can't know: I'd rather waste time and effort on stopping something that wasn't going to happen anyway, than do nothing and risk the worst case scenario.

Either way, one concorde isn't going to make the difference. Tesco be damned, every little doesn't help.

[JamieLei]

My personal thought is that the planet has experienced far more drastic changes in temperature and survived fine

Incorrect. The planet has survived far more drastic changes in temperature. We haven't. Humanity may have lived through the Younger Dryas rapid warming event 10,000 years ago, but evidence from studies of primitive communities in the Southern Levant showed that mass migration occurred with massive population decrease. Now that we're heading for a global population of 9-10bn, we simply don't have that flexibility. Let's just take global sea level rise, - how do you reckon societies will hold up if about 2bn people in Asia in delta regions are forced to migrate?

Secondly, the Gaia Hypothesis (see Lovelock, 2000) states that although Earth has its own mechanisms for preserving life, they are not the same mechanisms for preserving human life. Bacteria and plants will survive, but not human life. Our zone of tolerance is limited - if global temperatures rise 20°C, we're all screwed. Doesn't help that we're on course for global temperature rise of 3-5°C this century alone (see Crutzen, 2003).

I don't know all the science (if I did, I'd be a lot richer) - but then, nor does anyone else.

Excuse me, that's an extremely arrogant thing to say. "Oh I don't know the science, so noone else must be able to". I might be studying Physical Geography against my wishes at the University of Cambridge (at least in my second year I get to give the damn thing up in favour of Human Geography), but I can fully appreciate ALL the research that has gone into understanding the science, and you'll find that it's actually VERY comprehensive.

Just because you don't know what Bond Cycles, Dansgard-Oschler events, Oxygen isotope forcing, Milankovitch variables of procession, obliquity and eccentricity, Cenozoic orogeny forcing, ice-albedo feedback (at least EXTspotter knows this one!), Thermohaline circulation, and rapid acceleration in the melting of the Greenland Ice Sheet (the whole damn thing's on course to melt over the next 1,000 years, raising sea levels by 6m, or more when thermal expansion is taken into account); then it doesn't meant that noone else understands the science. There are other people in the world you know.

As for the whole "CO2 doesn't cause climate change" argument, I'm sure this graph (from Petit et. al., 1999) will solve your doubts.

I suppose there's a reason why the general public are not educated about the science behind climate change past the superficial level of the greenhouse effect and CO2 --> global warming. It's because it's just so damn complicated.

The problem is that we don't know where on the Fine<->Doom scale we are, and where we'll end up - and we don't really have any way to predict it other than "wait and see".

But we're already seeing. Temperatures have been rising continuously over the last 20 years, save for a blip in the early 2000s, and one in 1992 due to Pinatubo. Or are you one of those idiots who only span their temperature records over the blip and claim we're in a period of global cooling?

The simple thing for me though is that since we can't know: I'd rather waste time and effort on stopping something that wasn't going to happen anyway, than do nothing and risk the worst case scenario.

How selfish. Refer to the concept of Sustainable Development (see Adams, 2004; Carter, 2001). And the Bruntland Report (Brundtland, 1987): "Development that meets the needs of the present without compromising the ability of future generations to meet their own needs."

[openttd_rulez]

Can I also point out that as wonderful as a hydrogen engine that only produces water as an exhaust is, up at 30000ft contrails (which are formed by water vapour) are currently a bit of a pollution problem...

Oy, oy, more water vapour means more rain, more rain means cooler atmosphere, cooler atmosphere can reduce global warming.
P.S. Hydrogen aircraft engines will pump greenhouse gas called nitrus oxide straight into the ozone which is not good

[EXTspotter]

Hydrogen powered engines have the exact same problems as current engines where incomplete combustion leads to the production of Nitrogen (II) Oxide and Carbon Monoxide, however saying that its a reason why hydrogen engines are bad is a moot point as it would be the same with Kerosene powered engines. Also if you'd read the previous posts lots of water released that high doesn't form into cloud, hence does not cool the atmosphere like you claim.

Everyone keeps saying using hydrogen would be the best thing ever, however hydrogen is a whiley bugger. As it likes being a gas, its hard to compress, is highly flammable - read explosive - is so small it can leak from "sealed tanks", you cannot compress it enough to use it as a fuel without having to stop every half mile because you can not contain enough at a time. On top of this you would need an entire new infrastructure system for generating it and transporting it. Using other carrier molecules like metal halides is expensive and only very slightly less dangerous. In the end it just is not worth it if it is going to cause the same general problems that kerosene burning generates. Also the idea of using a hydrogen fuel cell to power it isn't great seeing as you cannot generate enough power, they would be prohibitively expensive, would have a very short lifespan and the proton transporter membrane in its core would split irrepairably after every landing. Basically you might as well use diamonds as a fuel for better, more cost effective, results.

[John]

After all, they're very thin and short lived.

The problem with contrails though is that there are a lot of aircraft up there producing them. A small effect produced by 150000 aircraft continuously is what is causing the issues.

If it wasn't a problem then they wouldn't be actively researching how to avoid them from forming.

Unfortunately I can't rally add any more as my notes on the aircraft pollution lectures are in England and my memory isn't that good

P.S. Hydrogen aircraft engines will pump greenhouse gas called nitrus oxide straight into the ozone which is not good

Hydrogen Engines produce nitrus oxide? And you are right in laughing gas being a polluter - cue the bad jokes.... (it's not a laughing matter!)

Or are you one of those idiots who only span their temperature records over the blip and claim we're in a period of global cooling?

But span the time scale up a few notches and we are due a period of significant global cooling.
Of course "we" refers more to planet Earth than our generation, or even the following few...

Rant about hydrogen solving all our problems

Quite, but I do wonder if Mr Benz ever thought that his invention would lead to something capable enough of flying 100 people at 60000ft at twice the speed of sound.

You have to start somewhere

[APDAF]

800 million years ago the earth was a big snowball but the CO2 was 10 times higher than today.

[Chris]

Won't happen this time.

[EXTspotter]

After all, they're very thin and short lived.

The problem with contrails though is that there are a lot of aircraft up there producing them. A small effect produced by 150000 aircraft continuously is what is causing the issues.

Contrails are mainly produced by large jet aircraft as to form the difference between the air moisture and the waste gas moisture has to be great enough for a cloud to form a cloud, which means they only form readily at higher altitude, e.g. over 12000ft. Also the global commercial jet aircraft fleet is nowhere near 150000, 20000 would probably be pushing it.

[JGR]

Hydrogen powered engines have the exact same problems as current engines where incomplete combustion leads to the production of Nitrogen (II) Oxide and Carbon Monoxide, however saying that its a reason why hydrogen engines are bad is a moot point as it would be the same with Kerosene powered engines. Also if you'd read the previous posts lots of water released that high doesn't form into cloud, hence does not cool the atmosphere like you claim.

Everyone keeps saying using hydrogen would be the best thing ever, however hydrogen is a whiley bugger. As it likes being a gas, its hard to compress, is highly flammable - read explosive - is so small it can leak from "sealed tanks", you cannot compress it enough to use it as a fuel without having to stop every half mile because you can not contain enough at a time. On top of this you would need an entire new infrastructure system for generating it and transporting it. Using other carrier molecules like metal halides is expensive and only very slightly less dangerous. In the end it just is not worth it if it is going to cause the same general problems that kerosene burning generates. Also the idea of using a hydrogen fuel cell to power it isn't great seeing as you cannot generate enough power, they would be prohibitively expensive, would have a very short lifespan and the proton transporter membrane in its core would split irrepairably after every landing. Basically you might as well use diamonds as a fuel for better, more cost effective, results.

I'm not sure if I follow how burning hydrogen gas in air produces carbon monoxide...

As for production, the main method used these days is steam reformation of methane, which kind of misses the point on the "green" and efficiency fronts. You could probably just burn the methane with a lot less hassle.
(Yes there are other ways like electrolysis of brine, but that's not exactly efficient (except in terms of it being a by-product))

At the moment there is *no* sensible alternative for powering aviation than combustion of hydrocarbons*
(*I'm happy for someone to prove me wrong, but I can't see it happening)

Also, what makes you think that a fuel cell membrane would split every landing?


Frankly "alternative fuels" like hydrogen and ethanol (at least in it's current incarnation), have just as many problems as the fuels they are replacing, and we should be wary of leaping onto them without looking first.

IMO in the near-term it'd be easiest to just copy the French and build lots of nuclear power stations and electric train lines, thereby reducing aviation demand and the amount of crud you need to burn somewhat.

[EXTspotter]

The breaking of the proton exchange membrane where it has occured in tests of previous FCVs as well as real world testing - i.e. the larger scale test going on in Southern California had shown that everyday driving lead to a gradual degrading of the membrane, most probably caused by small impact forces, e.g. driving into a large pothole. Modern PEMs are obviously much stonger than before, however it still continues to be a problem. A plane landing, if executed correctly is a very small impact force, however it must also be said that sometimes the effect of weather cold lead to harder than expected landings, e.g. pilots continuing wwith a landing after being suddenly hit by a strong crosswind gust or even something as stong as a microburst (however in that case the propulsion system is the least of your worries), even the effect of get there-itis (a psychological state whereby a pilot is pressurised by time contraints to continue a landing which is considered too dangerous to continue, however the pressure of time forces risk-taking - see AAL1420 - http://aviation-safety.net/database/rec ... 19990601-0 ). The research I have done into this subject isn't at a particularly high level - only A-level, so if this has all been disproved, etc, I apologise.

Btw, now you've mentioned it I was like, yeah, how does the C get in there? My head won't stop thinking about incomplete combustion of hydrocarbons