Jet contrails will likely affect climate by 2050

Climate impact of clouds made from airplane contrails may triple by 2050


In the right conditions, airplane contrails can linger in the sky as contrail cirrus – ice clouds that can trap heat inside the Earth’s atmosphere. Their climate impact has been largely neglected in global schemes to offset aviation emissions, even though contrail cirrus have contributed more to warming the atmosphere than all CO2 emitted by aircraft since the start of aviation. A new study published in the European Geosciences Union (EGU) journal Atmospheric Chemistry and Physics has found that, due to air traffic activity, the climate impact of contrail cirrus will be even more significant in the future, tripling by 2050.

Contrail cirrus change global cloudiness, which creates an imbalance in the Earth’s radiation budget – called ‘radiative forcing’ – that results in warming of the planet. The larger this radiative forcing, the more significant the climate impact. In 2005, air traffic made up about 5% of all anthropogenic radiative forcing, with contrail cirrus being the largest contributor to aviation’s climate impact.

“It is important to recognise the significant impact of non-CO2 emissions, such as contrail cirrus, on climate and to take those effects into consideration when setting up emission trading systems or schemes like the Corsia agreement,”

…says Lisa Bock, a researcher at DLR, the German Aerospace Center, and lead-author of the new study. Corsia, the UN’s scheme to offset air traffic carbon emissions from 2020, ignores the non-CO2 climate impacts of aviation.

But the new Atmospheric Chemistry and Physics study shows these non-CO2 climate impacts cannot be neglected. Bock and her colleague Ulrike Burkhardt estimate that contrail cirrus radiative forcing will be 3 times larger in 2050 than in 2006. This increase is predicted to be faster than the rise in CO2 radiative forcing since expected fuel efficiency measures will reduce CO2 emissions.

Radiative forcing due to the formation of contrails for present-day climate conditions and (a) present-day air traffic volume, and (b) for air traffic volume expected for the year 2050. Panels on the right hand side show the radiative forcing for climate conditions expected for 2050 and (c) air traffic volume for the year 2050, and (d) air traffic volume for the year 2050 assuming an increase in fuel efficiency and a 50% decrease in soot emissions. The numbers in the boxes show the global mean radiative forcing for each simulation.
CREDIT Bock and Burkhardt, Atmos. Chem. Phys., 2019

The increase in contrail cirrus radiative forcing is due to air traffic growth, expected to be 4 times larger in 2050 compared to 2006 levels, and a slight shift of flight routes to higher altitudes, which favours the formation of contrails in the tropics. The impact on climate due to contrail cirrus will be stronger over Northern America and Europe, the busiest air traffic areas on the globe, but will also significantly increase in Asia.

“Contrail cirrus’ main impact is that of warming the higher atmosphere at air traffic levels and changing natural cloudiness. How large their impact is on surface temperature and possibly on precipitation due to the cloud modifications is unclear,” says Burkhardt. Bock adds: “There are still some uncertainties regarding the overall climate impact of contrail cirrus and in particular their impact on surface temperatures because contrail cirrus themselves and their effects on the surface are ongoing topics of research. But it’s clear they warm the atmosphere.”

Cleaner aircraft emissions would solve part of the problem highlighted in the study. Reducing the number of soot particles emitted by aircraft engines decreases the number of ice crystals in contrails, which in turn reduces the climate impact of contrail cirrus. However, “larger reductions than the projected 50% decrease in soot number emissions are needed,” says Burkhardt. She adds that even 90% reductions would likely not be enough to limit the climate impact of contrail cirrus to 2006 levels.

Another often discussed mitigation method is rerouting flights to avoid regions particularly sensitive to the effects of contrail formation. But Bock and Burkhardt caution about applying measures to reduce the climate impact of short-lived contrail cirrus that could result in increases in long-lived CO2 emissions, in particular given the uncertainties in estimating the climate impact of contrail cirrus. They say that measures to reduce soot emissions would be preferable to minimise the overall radiative forcing of future air traffic since they do not involve an increase of CO2 emissions.

“This would enable international aviation to effectively support measures to achieve the Paris climate goals,” Burkhardt concludes.


The publication is in Atmospheric Chemistry and Physics – link to the paper 

Some thoughts:

  1. This is a model output, so take it with a grain of salt.
  2. They seem to only consider the Long Wave IR to space reflectivity for contrails as being the big forcing component, yet there’s a big reflectivity factor for incoming solar radiation too. And, that’s got to be considered. If contrails were only reflective one way (from the surface looking up) we’d not be able to take photographs like this one from space:
Jet contrails as seen by satellite. Credit NASA Langley Research Center

NOTE: Any discussion of “chemtrails” in this comment thread will be immediately deleted. -Anthony

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Dave Fair
June 27, 2019 10:15 pm

There was no quantification of the current warming from contrails. Any increase could (will) be de minimis.

Joel O'Bryan
Reply to  Dave Fair
June 27, 2019 11:59 pm

not even a 1/10th of the nose level. Unquantifiable outside of some BS cargo cult model simulation, where they hide the huge error (uncertainty) bars, as they always do.

Reply to  Joel O'Bryan
June 28, 2019 1:43 am

Agree, just like CO2 emissions.

Reply to  Joel O'Bryan
June 28, 2019 5:46 am

It does not matter whether the effect is immeasurable, the aim is to build an agenda for banning air travel for ordinary citizens. The way they blatantly only look at one side of the equation before drawing conclusions makes it obvious this is not about science.

Reply to  Greg
June 28, 2019 6:07 am

Why do you think this is the last thing the academics wanted to look at?
(Hint: academics fly more than many other groups)

Gunga Din
Reply to  Greg
June 28, 2019 7:35 am


Bill Murphy
Reply to  Joel O'Bryan
June 28, 2019 10:28 am

While looking for the paper I mentioned below, I found this from 1970:
Airborne Observations of Contrail Effects on the Thermal Radiation Budget
“Direct infrared and solar radiometric observations were made to analyse the effects on the environment of any alterations in the radiation budget in regions of heavy jet traffic. The observations, made from the NASA Convair 990 jet laboratory, were coupled with Mie scattering and absorption theory calculations to analyze any inadvertent alterations in the natural atmospheric thermal radiation budget. It was found that a 500 m thick contrail sheet increases the infrared emission below the sheet by 21% but decreases the solar power below the sheet by 15%. The infrared increase cannot make up for the solar depiction, resulting in a net available incoming power depletion at the base of the sheet of 12%. Such a change at altitude results in a 7% reduction in the net total available thermal power at the earth’s surface, which, in turn, results in a 5.3C decrease in the surface temperature, if we assume contrail persistence. The actual temperature decrease is ∼0.15C with 5% contrail persistence.”

Net cooling! Did the European Geosciences Union bother to search the existing literature? Or were they more interested in adding to the propaganda.

Reply to  Bill Murphy
June 28, 2019 1:17 pm

Bill, this article confirmed my immediate response to the headline: contrails are visible, hence they reflect visible light, hence they remove energy from “above the greenhouse.” HOWEVER: where there is smoke there is fire / where there are clouds there is water vapour. We all know that non-condensing water vapour is the dominant greenhouse gas. Perhaps the invisible aircraft contrails are a larger problem than the visible ones?

PJ Moran
Reply to  boffin77
July 1, 2019 9:11 am

Has every one forgotten 9/11 and the grounding of all non military US aircraft flights for several days? It warmed the temperature. No clouds, no shade. Rain from clouds cools surface temps.

Robert W. Turner
Reply to  Bill Murphy
June 28, 2019 2:21 pm

It’s really amazing isn’t it? I couldn’t believe the last sentence of the article so I had to look. The paper doesn’t even include the words albedo, solar, or reflection. There’s no way they can be this dumb so it must be pure fraud. Propaganda is something documentary makers and governments do, in science it’s fraudulent.

Reply to  Bill Murphy
June 29, 2019 12:09 am

Thanks for the link Bill, that paper looks much more informative.

I looked at the paper this article refers to and it is not at all clear what they are considering. It seems based on an earlier paper where they report on the model they used in creating this paper. They seem to be involved in propaganda , not science, so I did not waste my time chasing that any further.

They are clearly out to produce results to justify restricting air travel on the assumption that it is “bad”. Ironically, since particulate stratospheric pollution and cloud seeding are actually cooling the planet, reducing plane travel will likely have the opposite effect of what they claim: global warming. OOPS !

R Shearer
Reply to  Dave Fair
June 28, 2019 5:52 am

Jet fuel also contains sulfur compounds that form SO2 upon combustion, which subsequently reacts to SO3 and forms reflective aerosols.

That sulfur level is declining with regulations that remove sulfur from other distillates, especially diesel.

Reply to  R Shearer
June 28, 2019 7:17 am


Bryan A
Reply to  Dave Fair
June 28, 2019 10:33 am

One potential solution would be to restrict air traffic to below the altitude thresholdat which Contrails form about 26,000′ – 35,000′. Limit Air Traffic to below 25,000′ and trails do not form for most of the year

Reply to  Dave Fair
June 28, 2019 11:24 am

There is NEGATIVE warming from contrails.

9/12/2001 and 9/13/2001 had a ground level heat spike of about 2°F because of a LACK of contrails. Those were the days that air traffic was grounded across North America.

June 27, 2019 11:19 pm

I thought clouds had a net cooling effect ? Yes they warm at night, but during the day they reduce the overall incoming radiation which has a larger cooling effect than the night time warming,

Mark - Helsinki
Reply to  ggm
June 28, 2019 12:12 am

Altitude. Clouds high enough trap and reflect, but definitely trap.

Lower altitude mostly reflect

Reply to  Mark - Helsinki
June 28, 2019 4:52 am


Reply to  DHR
June 28, 2019 6:09 am

It’s not about trapping – instead the cloud is blocking IR from the ground and replacing it with IR from the cloud. That IR from the cloud is at the temperature of the cloud, so the higher it is, the colder it is, the less IR that is emitted.

So, relatively high temperature IR being emitted from the ground is replaced by relatively low temperature IR being emitted from the cloud and there is a reduction in IR.

Robert W. Turner
Reply to  Mike Haseler (Scottish Sceptic)
June 28, 2019 2:26 pm

Yes but they are reflecting/absorbing incoming visible and IR light. The net effect is cooling. I don’t think they stick around too long into the night.

Richard M
Reply to  DHR
June 28, 2019 6:57 am

My understanding is that at lower altitudes the greenhouse effect is generally saturated. It is only as get higher that photons are most likely to make it into space. In addition, you are also above most of the clouds which are also radiating from their tops. This expands the area that is available to absorb photons to near 100%.

Bryan A
Reply to  DHR
June 28, 2019 10:37 am

Higher clouds tend to be thinner allowing SW IR to pass through but also reflect LW IR.
Lower clouds tend to be denser and reflect incoming SW IR negating the LW IR from being reemitted (Cloud base height and density is the key)

Walter Sobchak
Reply to  DHR
June 28, 2019 1:06 pm

Don’t ask why. It is Settled Science. What are you? A denier?

Reply to  Mark - Helsinki
June 28, 2019 5:53 am

But at higher altitudes there is little to no heat to “trap”

Dave Fair
Reply to  ggm
June 28, 2019 9:03 am

Its not heat, its energy.

Farmer Ch E retired
Reply to  Dave Fair
June 28, 2019 9:20 am

Heat is one form of energy but energy can be other things as well (kinetic, potential, etc, etc)

Old England
Reply to  ggm
June 28, 2019 1:10 am

Is night time “warming” the correct phrase? The amount of night time Cooling is slightly lessened, temperatures are not increasing after sunset …… except perhaps in some urban environments where heat is being given off from buildings ….

Reply to  Old England
June 28, 2019 5:11 am

The unfortunately statistically inconclusive study of warming/cooling during the post-911 grounding of US air traffic, showed a few degrees of warming IIRC. Though it was not possible to exclude the possibility that a natural variation could have caused this.

The nearest thing we had to an actual climate experiment showed that less flights=global warming.

Also both El Chichon and Mt Pinatubo stratospheric eruptions ( which concerns exactly the heights where most commercial flights pass ) resulted in a cooling of the lower stratosphere in the years which followed. This implies greater transparency.

That greater transparency allows more solar into the lower atmosphere and accompanied the period of “catastrophic” warming arbitrarily attributed to AGW.

It seems likely that the removal of avionic pollution caused warming. Again, contrary to what this one-eyed study is trying to concluded.

Of course, if they had found that more flights mitigated AGW, they would not have got published, would have been ostracised by the climate community and would have lost all funding.

June 27, 2019 11:29 pm

Earth: an ancestor simulation to see if humans would argue about an essential just above starvation level photosynthesising useful trace gas 😀

Dodgy Geezer
June 27, 2019 11:51 pm

I thought that one of the big problems with Global Climate Models was that they couldn’t tell whether clouds were, on balance, positive or negative forcing?

Reply to  Dodgy Geezer
June 28, 2019 2:51 am

“…that they couldn’t tell whether clouds were, on balance, positive or negative forcing?”

Unless they are man-made clouds, which creates an additional suitable leverage-point for the activists for their blame-pinning.

Reply to  Johanus
June 28, 2019 4:31 am

Yeah, GCMs don’t actually model clouds, but add in a postulated effect for clouds.

June 27, 2019 11:51 pm

See! I said we were doomed!

Joel O'Bryan
June 27, 2019 11:57 pm

due to air traffic activity, the climate impact of contrail cirrus will be even more significant in the future, tripling by 2050. ??????
I thought we were supposed to be extinct by just after 2030??? End of fossil fuels because we’re all fire-roasted marshmallows (heat charred on the outside, gooey soft in the middle) and all that.
You know… Climate catastrophe, climate weirding, climate collapse and all that Watermelon bull schist.

Bill Murphy
June 28, 2019 12:01 am

As far back as the 1970’s there has been talk about contrail weather and climate effects. A paper somewhere around 1973 or so talked about possible negative effects of contrails dimming sunlight on agriculture. That paper also discussed how contrails, in certain conditions, can grow into sizable banks of cirrus, an effect I personally have witnessed many times from the ground and the air. What the net effect might be on global energy balance is debatable. A freshman level atmospheric sciences class I took about the same time in the 70’s claimed cirrus are net heaters while cumulus are net coolers and stratus can be either depending on thickness of the layer. All I know for sure is a cirrus between me and the sun is welcome when mowing the lawn in summer and irritating when shoveling snow in the winter — it feels cooler.

Tom in Florida
Reply to  Bill Murphy
June 28, 2019 5:18 am

I used to play golf a lot and when cirrus clouds were present it was a pretty sure bet that there wouldn’t be any thunderstorm development and thus no lightning. We always liked it when the cirrus clouds appeared as it allowed us to just go and play without worry.

Michael S. Kelly, LS BSA, Ret
June 28, 2019 12:03 am

I recall an article on this subject from a few years ago, but can’t find it. Immediately after the 9/11 attacks, all air traffic in the United States was halted for several days. “Scientists” used the opportunity to check the effect this had on global warming. I forget what they found, but it was an actual case of a large-scale change in human contributions to environmental change, and thus, to global warming.

Crispin in Waterloo but really in Mersing
Reply to  Michael S. Kelly, LS BSA, Ret
June 28, 2019 1:26 am

The increase attributable to the absence of contrails was one degree C.

Reply to  Michael S. Kelly, LS BSA, Ret
June 28, 2019 2:38 am

Here it is
It only says the temperature range increases, not if contrails warming or cooling.
BUT… clouds have a cooling effect

Ian W
Reply to  Michael S. Kelly, LS BSA, Ret
June 28, 2019 3:26 am

The NASA scientists involved did not mention that the 9/11 attacks occurred when there was a large dome of high pressure over the East coast that would have led to cooling in September. They instead blamed cooling on the lack of contrails – there probably would have been no contrails anyway. Contrails only occur in high humidity which is why on many days there are a none and others they are very apparent. The number of flights is around the same it is just that there may be insufficient humidity at the aircraft cruising levels for contrails to form.

Reply to  Ian W
June 28, 2019 7:03 am

Contrails only occur in high humidity which is why on many days there are a none and others they are very apparent.

True. I live under an area of major flyover routes in the US central Appalachians, and there are many more days of zero to hardly any contrails than numerous/persistent contrails.

Reply to  beng135
June 28, 2019 10:26 pm

In Sydney, there are far fewer persistent contrails than we see in the US, even accounting for the smaller number of flights. The typical contrail behavior above the Sydney area is for contrails to be about 1km long, and dissipating, if they are visible at all. You might see one or two that last for more than 1/2 hour once a day, if that.

Seems our typical humidity at altitude, combined with a generally lower number of particulates, restricts them from forming the “streets of cloud” we see in the US.

Samuel C Cogar
Reply to  Ian W
June 28, 2019 8:21 am

Contrails are much, much more visible EARLY in the mornings, just before the Sun rises above the horizon.

The reason being that, …. with the sun “rising” in the East its sunshine will be “reflected” off the underneath of the contrail’s water vapor droplets, ….. thus making them visible from the surface if the viewer is underneath or to the west of the rising Sun.

And as the Sun climbs higher above the horizon …. the contrails start disappearing as if there was “magic” involved.

Richard Patton
Reply to  Samuel C Cogar
June 28, 2019 8:19 pm

A similar thing goes for the nearly always present layer of CI at 30K in the tropics. You can only see it at sunrise and sunset. I remember when on Guam the two observations around sunset and the two around sunset always had 300 -OVC (30,000′ thin overcast)

Reply to  Michael S. Kelly, LS BSA, Ret
June 28, 2019 3:56 am

i noted the massive increase in sky clarity in pics from then
i also note our rural skies cloud over after as litle as 6 planes do a series of runs over my area and a nice clear sunny day becomes dull and not so nice.
the greenvirgin branson plans hundred more planes in air for his profit..carbon offsets my a$$
dont get this mindless jump on a plane go somewhere mindset people have, at all.
for Ausies its cheaper to go to asia for a fortnight than one week in our own nation for a holiday, yet fuel etc use is so much more.

Craig from Oz
June 28, 2019 12:07 am

Remind me – After the September 11 attacks all air traffic in US airspace was stopped for… 3 whole days(?)

If I recall correctly there was a measurable change in recorded temperatures during this period because there were of course no contrails getting between the ground and the sun.

And, correct me if I am remembering wrong, but the observation was that WITHOUT contrails in the sky… IT GOT HOTTER.

These people are either desperate or lacking in basic reasoning abilities. If the models do not match the observations, then it is probably your models.

Reply to  Craig from Oz
June 28, 2019 1:58 am

A quick Google showed plenty of articles on the effects of stopping air travel after 9/11, here is the first:

The big effect of removing contrails was an increase in temperature range of about two degrees Celsius.

So contrails cool during the day and warm during the night, net change seems to be warming, but that is smaller and so less certain.

June 28, 2019 12:08 am

Contrails are net cooling. More contrails means more cooling.
Quoted from

“consensus of the experimental and model findings given here suggests that the climatic effects of contrails, persisting on the order of minutes to hours, may more likely lead to a cooling of the surface of the earth
rather than to greenhouse warming”

June 28, 2019 12:13 am

Next we’ll have Ocasio-Cortez screaming that the high temperatures from jet engines and car engines heat the planet. 🙁

Reply to  joe
June 28, 2019 2:35 am

Someone who would say that is correct. There is a lot of waste heat released into the atmosphere through electricity generation, internal combustion engines, heating and air conditioning buildings. Cooking releases heat into the atmosphere.
I would theorize that the waste heat released into the atmosphere is the sum of all human contributions to “global warming.”

Reply to  DonK31
June 28, 2019 3:02 am

Every type of energy will transform to heat.
Do you know that the energy realeased by human over the last 40 years would be egnough to heat ALL water in the Mediterranean sea?
Not so much in the big picture, but a human caused global warming that is real and not fake like CO2

Farmer Ch E retired
Reply to  joe
June 28, 2019 3:33 am

Much of the engine heat (from my limited expertise) comes from the inefficiency of extracting work from combustion. Liquid fuel is burned producing vapor byproducts where latent heat of the vapor is not recovered as work by the engine. So while the engine does lose heat, it also emits water vapor as a combustion product which acts to increase the dew point and thus the nighttime minimum temperature. Regarding contrail vapor, jets generate maybe twice the water vapor per hour on take off (while moving slower) than they do at altitude (at cruse speed). As such, one would expect an increase in nighttime minimum temperature, especially in the areas around airports.

Someone with actual data or experience – please add to or correct my understanding.

R Shearer
Reply to  joe
June 28, 2019 5:49 am

By 2030, all air travel will be displaced by high speed rail. Of course, this only lasts for one year until the world ends.

Patrick MJD
June 28, 2019 12:17 am

What is it with the year 2050? Everything must be done to stop climate change, in 30 years! It’s like fusion, always 30 years away.

Mark - Helsinki
June 28, 2019 12:19 am

The real question is why the change.

It is absolutely true that contrails did not behave in this way in the past. That is to say, persisted and spread out into massive clouds. Has the fuel changed. I did read somewhere that more sulfur is added to fuel for more pressure for high altitude flight. This would have an effect?

Going by the sat images of the UK of contrails being persistent and spreading out, it absolutely affects the energy balance, how I don’t know.

Why do contrails now all too often plaster the whole sky and often even here in Finland make the whole sky silver.. is a question I wonder about.

Is adding more sulfur to fuel a way to experiment with SRM?

No idea, no conspiracies 😀

Reply to  Mark - Helsinki
June 28, 2019 1:25 am

More airplanes, much more. And contrail amnesia.

Reply to  Mark - Helsinki
June 28, 2019 2:32 am

There are many contributing factors for a change in condensation trails in Finland.

At higher altitudes, wind speeds are higher. So airliners want to be as high up as possible, if they can catch a tail wind.
– With the use of larger, more powerful engines, airliners can fly higher.
– Thanks to composite hulls, airliners can better withstand fatigue.
– The reduction of costs, has led to an increase of passenger numbers.
– With newer, long range models, polar routes between Europe and Asia have become an option.
– Thanks to long range models, the Hub and Spoke model is no longer needed. Airliners can use small, less congested, low cost airports.
– China has become a more important destination.

Every time I read about some nutty professor trying to use SO2 for Geo-engineering, I think; Just stop removing Sulfur from Jet-A.

Bill Murphy
Reply to  Mark - Helsinki
June 28, 2019 9:55 am

It is absolutely true that contrails did not behave in this way in the past. That is to say, persisted and spread out into massive clouds.

Not true. The paper I mentioned above talked about this happening in the 1970’s and I have heard anecdotal stories from WWII pilots that the contrails left by the Allied bomber formations over Europe occasionally spread out to form solid cirrus layers that would play havoc with the later follow-up photo recon missions, forcing them down to lower (more vulnerable) altitudes to complete their missions. Persistent contrails and contrail seeded cirrus layers have been around a long time.

June 28, 2019 12:38 am

It was very noticeable in 2010 when the eruption of the volcano (with the unpronounceable name) resulted in all air traffic being grounded for a number of days. The immediate effect was the very clear blue skies and an apparent increase in sunshine intensity, very similar to the intensity the I experienced in New Zealand.
When they allowed the air traffic to resume it was also noticeable that the intensity fell, and how quickly the sky filled up with what seemed like very thin clouds.
There didn’t seem to be any warming effect, if anything the opposite.
Some photos I took showed the effect of the contrails, but I should have also taken some photos while the air traffic ban was in force.

Dodgy Geezer
June 28, 2019 12:52 am

“Jet contrails will likely affect climate by 2050”

Er – won’t we be using matter transfer to beam us to our destinations by 2050?
Or Gravity Trains ( )?

We’ve been waiting since Hooke invented the idea in the 16th century for these. A bit longer than our ‘flying cars’….

Right-Handed Shark
Reply to  Dodgy Geezer
June 28, 2019 6:05 am

The IPCC has had one since it’s inception. Btw, you misspelled ‘gravy’.

Stephen Richards
June 28, 2019 1:11 am

They have been saying this for maybe 40 years and have never provided evidence

June 28, 2019 1:12 am

“Aircraft contrails can spread into cirrus-like clouds high in the atmosphere. Similar to natural clouds, they are thought to have an overall warming effect on the planet. But they can also moderate daily temperature extremes by trapping heat that escapes from the ground and reflecting sunlight. This raises the lowest overnight temperatures and, to a lesser degree, reduces the highs during daylight hours, scientists have suggested.”

Reply to  jmorpuss
June 28, 2019 3:45 am

“When all commercial air traffic in the United States was grounded after the terrorist attacks of 11 September 2001, scientists got an unexpected opportunity to test ideas about the climate effects of the condensation trails left behind by jets.”

Flight Level
June 28, 2019 1:18 am

(united nations)” ignores the non-CO2 climate impacts of aviation”

Yeah, that’s why you pay in EU a very creatively calculated few bucks of NOx mitigation tax included in the ticket price.

Although I have never seen NOx mitigation machinery units being financed with those taxes. Collected money just vanishes as usual.

Chemtrails are produced by high performance aircraft. Nothing to worry since by 2020, 2030, 2050, anywhere around there, birds, blimps and electric aircraft are the only supposed to fly.

Not far away from where I live, a small company (2 on payroll) attempts to put 1’800 kg of batteries in a Cessna 172, stretch it’s fuselage and add a second electric motor in the tail section.

To the latest news, first transatlantic flight is expected to occur in 2020. We all wish them good luck.

Reply to  Flight Level
June 28, 2019 2:29 am

By 2050 The West will be even more bankrupt. Poor people don’t fly.

Flight Level
Reply to  Robertvd
June 28, 2019 3:34 am

Right Robertvd, reason why I suggested my kid to become a lawyer. The more poor, the more rich will need legal means to contend them.

Reply to  Flight Level
June 28, 2019 4:55 am

While concern about the environment is mounting, the willingness to invest in change is going down, the SCP said. This, the researchers say, has been boosted by the sharp rise in energy bills – some €330 a year – which became apparent in January.

‘The environment used to be a left wing pastime for people who drove an electric car and had solar panels on their roof,’ researcher Paul Dekker told Trouw. ‘But the rise in fuel bills and the decision to phase out the use of gas have brought the issue home to people on low and middle incomes… and they think it is going to cost money.’

Flight Level
Reply to  Robertvd
June 28, 2019 6:00 am

Robertvd, on the other side of the pond, everyone gives priority to job preservation. In other words, our economy is bingo fuel and whatever’s left on saving accounts is preyed by means of ever creative tax scenarios.

It kind of smells ozone, we’re on the way to a big nasty cloud of social unrest and there seems not to be detours or alternates within reach.

Our history is seemingly a wheel. Or people wake up and vote the greens out or, when the vitrified ground cools down, contrails would be the least of tings to worry about.

Because, happens, one day or the other, UN could intervene and “politely enforce” Russia to shut down and terminate it’s oil, coal & mining industry…

Then… Is there really a “then” clause ? Hey, we’ve been there already, we still remember the consequences of a mad inhumane ideology.

Reply to  Robertvd
June 28, 2019 3:36 pm

330 euros a year? Californians pay that much a month.

sky king
Reply to  Flight Level
June 28, 2019 2:45 pm

Neat trick for an airframe rated for 1111kg max takeoff weight. I don’t want to be in their flight path when they attempt the first flight.

Flight Level
Reply to  sky king
June 28, 2019 4:27 pm

Indeed Sky King. 30 or so more miles NW, another heavily sponsored company tries a stretch ultralight hybrid. Think a 4 seater scaled down Trislander with only the aft prop driven by an electric motor.

In front, a Rotax + generator, 5 gallons gas tank, cooling system. And 400kg of batteries in the wings. Solar cells allover.

Take-off & climb on electric engine, cruise on gas for flight and recharging batteries, landing on electric. Go-rounds on gas + electric. No flaps / slats, fixed gear

A few thousand of those operated in self-fly pilotless mode are supposed to take care of all regional traffic.

Now even without contrails, that’s a scary movie !

Jeff Guinn
June 28, 2019 1:31 am

Back in the day, I had a friend who was an Air Force meteorologist.

He said contrails gave him fits, because their existence and development are so difficult to predict.

On days where they were not expected, yet nonetheless formed and spread, surface temperatures would be as much as 6ºF cooler than forecast.

I know, weather isn’t climate, nor data.

I shall report to the punishment booth.

Richard Patton
Reply to  Jeff Guinn
June 28, 2019 8:26 pm

Jeeze, I’m glad that all of my forecasting billets were where the temperature was strongly controlled by the very nearby oceans, (Guam, Hawaii, and onboard ship) or in the very dry desert (Nevada). I never had problems with not hitting my temperature forecast because of cirrus. I guess that some people can’t be lucky.

June 28, 2019 1:56 am

Add some reflective particles to exhaust and scattering mechanism. There you go geo-engineered cooling.

Reply to  Stevek
June 28, 2019 2:35 am

Just stop removing Sulfur from Jet-A and you get some nice shiny SO2 bubbles at high altitude.

Flight Level
Reply to  RLu
June 28, 2019 6:09 am

Nah…. Maintenance guys dont like what that stuff does to the hot sections.

And grumpy maintenance is realistically much fearsome than any global or local warming, altogether.

June 28, 2019 2:29 am

“NOTE: Any discussion of “chxxtrxxls” in this comment thread will be immediately deleted. -Anthony”

And I was just about to get out my tinfoil hat. Spoilsport. 🙁

This article triggered one of my early memories of my father: When I was about 5 or 6 years old I gave him the benefit of my vast experience and scientific observations and declared that clouds were made by aeroplanes. He gently gave me the benefit of his even vaster experience and let me know I was wrong. 🙂

Jeff B
June 28, 2019 2:55 am

This seems like a spoof. You gotta be kidding me. What’s next? Skiers are a major contributor to climate change by 2050 because of the change in albedo due to colored skiwear. I’ll write up a paper shortly.
The BS. Ever ends.

Reply to  Jeff B
June 28, 2019 4:08 am


You might need help on that project. I think an externally funded trip with our families …er…highly qualified research assistants, to 30 of the planets key ski resorts is essential in order to carry out the vital research of the coloured ski wear hypothesis.


June 28, 2019 3:25 am

Every day there is a chequer pattern of contrails criss-crossing the skies over London, but they dissipate almost immediately.

It’s nice to know we’ve got air cover, I suppose.

Russ Wood
Reply to  fretslider
June 28, 2019 8:07 am

Some years ago, visiting the UK from Johannesburg (where we rarely get contrails), my wife snapped a picture of contrails over Liverpool forming a ‘noughts and crosses’ pattern. (Maybe the ‘Pool is an airway crossing point). Anyway, seeing this, she remarked “OK, God – play the ‘X'”.

Coeur de Lion
June 28, 2019 4:01 am

I’m going to fly as often as possible in my old age to cool the planet.

Reply to  Coeur de Lion
June 28, 2019 3:39 pm

And in my old age I will sit under your contrail to stay cool.

June 28, 2019 4:26 am

Well let’s have a reconstruction study from 1943 to April of 1945. During that period of WW II 1,000s of allied aircraft at a time were flying from Britain and later Italy to Germany over Europe every day weather allowed. Huge formations of US B-17 and B-24 four engine bombers flying in tight formations and the fighters escorting them often left clouds of contrails during their day light raids. The British heavy bombers however, flying at night, regularly changed altitude to try and prevent leaving contrails since they were a dead giveaway to German night fighters. Then add 1,000s more 2 engine medium bombers and their escorting fighters in the last couple years of the war hitting targets in Europe.

And yes, those reciprocating engines did leave heavy contrails. And yes, the 2 engine medium bombers often flew missions high enough to leave contrails.

June 28, 2019 4:28 am

It appears that these purported scientists ( Burkhardt et al) suffer the same belief that I suspect many do:
Namely that CO2 is a dirty great DUVET up in the sky and will eventually cook us as it’s Tog rating increases.
Being oblivious of the basic thermodynamics and the behaviour of water they struggle to comprehend so regurgitate the rubbish they have picked up from others with similar problems.

The cirrus clouds nudging the Tropopause contain ice crystals at very low temperature (around -50C) and these grow dendritically so are radiating more energy than they receive.
This radiated energy goes to space and results in a weight increase in the crystals due to the loss of the Latent Heat of fusion.
At a certain point gravity causes the crystals to fall and decend through the atmosphere sucking up energy as they morph towards the liquid form winding up as rain, snow or hail depending on circumstances.
The whole process is a wonderful way to cool the planet. Need I say more? you may draw your own conclusions from this; but there is much more to say albeit more complicated if you want to understand why the Satanic CO2 Meme is such a scam.

I have a trite saying for what it is worth: “The Earth sweats to keep cool, just like you and I”

June 28, 2019 4:32 am

Anthony, thank you for posting this article. I have been troubled and annoyed with the contrails and was hoping you’d post something about their effects. I yearn of my childhood days when the skies were fantastically blue and cloudless which are rare today.

Reply to  Jenn
June 28, 2019 5:54 am

How old are you ? 300 y ?

We all have such fond memories of childhood summer days but that is the result of heaving reporting bias, publication bias and nostalgia.

You will probably find that air was more opaque back then due to lower down industrial pollution. Records of cloud “amount” are about as vague as that term sounds. It’s actually quite hard to even define what you should be measuring.

Reply to  Greg
June 28, 2019 8:17 am

Where I grew up and where I live now are the same – in a rural area where I could see for miles without a cloud in the sky and no pollution to even mention. The contrails then were sparse – 2 per day from Airforce jets which were very distinct but not so today as the sky is often hazy and cloudy from the many dissipating contrails. Please refrain from attempting to gaslight me into disbelieving my own dependable observations.

Richard Patton
Reply to  Jenn
June 28, 2019 8:33 pm

There is also the point that 60 years ago most commercial flights were 18-25Kft, Today they are 35-40Kft or even slightly higher, especially trans-Atlantic or trans-Pacific flights. 18Kft is just barely into the Cirrus cloud levels. 35-40Kft are deep into that area, and in the winter the only cirrus clouds that high are contrails. (Summer or the tropics is a different story-I have seen a CB anvil measured by radar at 85Kft)

June 28, 2019 5:18 am

Based on a quick scan of the comments, I’m glad I didn’t waste any time finishing the article.

OMG! Infant deaths TRIPLED in my community over the last decade!

Horrible news, right? Until you put it in PERSPECTIVE.

Ten years ago, ONE infant died from disease. Last year, two died in an auto accident. AND my community has a million people in it.

So, (I’m not going to bother finding the exact quotes) if contrails TRIPLE THEIR anthropomorphic effect and become a larger part of that effect, how do we know it will have ANY effect on the overall climate?

What is the percentage of CLIMATE (NOT climate CHANGE) that is “anthropomorphic”? Would be a relevant FACT (not really since that would be a fart it out of my ass guess) to include in the article.

I could go on, but it looks like the other commenters are taking this waste of time apart already.

Nick Schroeder
June 28, 2019 5:46 am

Energy is a thermal property.
Heat is a thermal process, i.e. energy in motion from hot to cold.
Temperature is the comparative measurement of the kinetic energy in a molecular system.
No molecules = no temperature just like no molecules = no sound.

The notion that energy/heat gets “trapped” is thermal nonsense.

Gary Mount
Reply to  Nick Schroeder
June 28, 2019 7:57 pm

A volume with no molecules can still contain radiation, hence the temperature of the vacuum of space is about 3.5 Kelvin.

Geoff Sherrington
June 28, 2019 5:50 am

The current farce named “Climate Science” is proceeding via the attribution of horror after imagined horror to “Climate Change” in the broad sense. The ultimate, terrifying accumulation of all of these disasters is so large that even a child can detect existential threats to the whole human race. And children do, and some make headlines. It just gets better as more imaginations are allowed publicity and the terrors increase in intensity and scope. What a way to go.
Those of us who are heartily sick of this negativism look for some relief from the pessimism. We read papers involving atmospheric hots and colds attributed to clouds. They can cause big w/m2 changes with very little effort, but we optimists feel that there should be a fair chance that Nature has a balance, that some cloud changes will be hot, some will be cold in overall effect. Indeed, people like me look for papers where climate change is a benefit, not yet another fictional horror story.
The past indicates an absence of irreversible tipping points; this might indicate that there are both positive and negative feedbacks that tend to balance around a livable range for humans.
So why the heck does our pathetic crop of climate scientists rabbit on with negativism, while some of us older. more wise to the world scientists say that conditions for human life and comfort and enjoyment have never been better?

Dave O.
June 28, 2019 6:01 am

Humans could possibly, theoretically, hypothetically, potentially, maybe, perhaps, conceivably destroy the planet.

Reply to  Dave O.
June 28, 2019 6:16 am

So you’re saying there’s a chance?



Gunga Din
Reply to  ripshin
June 28, 2019 7:43 am

I think he just might be implying there could be.

Dave O.
Reply to  ripshin
June 28, 2019 4:08 pm

zero chance. But, have to keep everybody nervous.

June 28, 2019 6:02 am

Aircraft contrails are not clouds.

In addition to failing to consider the reflective effects of clouds both from the ground up and from the contrail up, these researchers totally ignore the “edge effect”.

Very low clouds do tend to “trap” or reflect radiative heat emanating from the ground or water surface, but only when they cover a relatively large contiguous area. Contrails are extremely narrow and diffuse, and the edge effect of such narrow ice crystal formations likely overwhelms any other effects wrought by the reflectivity of the ice crystals.

This is half baked science – come back to us when you have a fully baked solution.

The Depraved and MOST Deplorable Vlad the Impaler
June 28, 2019 6:19 am

“… even though contrail cirrus have contributed more to warming the atmosphere than all CO2 emitted by aircraft since the start of aviation.”

It would appear that I’m mis-understanding something here: cirrus are crystals of water vapor, so it sounds as though water (in all its various forms) is a stronger control on climate than the demon gas.


June 28, 2019 6:31 am

What an unlikely scenario!
By 2050 the EU’s irrational economic model of crony capitalism would have ensured that any wealth they had has been wasted away.
So why would anyone want to visit a bunch of 3rd rate nations where millions of unrepaired windmills sit idle, where decomposing solar cell detritus pollutes the land and water — to gawk at all their fancy minarets, travel on their poorly maintained and unreliable trains and roads to yet another dirty city or abandoned rotting industrial parks?

June 28, 2019 6:31 am

When they doubled back, I always thought that they must have forgotten something.

michael hart
June 28, 2019 6:32 am

So what makes them think they sufficiently understand human-created clouds when they don’t understand the natural ones?

It’t the underlying theme in climate science: they can’t model the natural climate adequately but insist they can adequately model the same climate with added human complications. Unbelievable.

June 28, 2019 6:37 am

This scenario makes no sense to me. It only works if cirrus clouds are transparent to incoming solar radiation but reflective to outgoing. But don’t all clouds, whether made of ice particles or water droplets, increase albedo, hence deflect larger amounts of incoming radiation? Am I missing something here?

June 28, 2019 6:37 am

Simple solution for the green-loons — just add sulfur to the jet fuel. Burns to SO2 — viola.

June 28, 2019 6:42 am

I am betting that the image at the bottom of the post is an hours-long exposure, exaggerating the effect.

June 28, 2019 7:18 am

Just ban Airbus production out of an abundance of caution.

R Shearer
Reply to  ResourceGuy
June 28, 2019 2:17 pm

Good one.

June 28, 2019 7:18 am

The Key Statement: “Contrail cirrus’ main impact is that of warming the higher atmosphere at air traffic levels and changing natural cloudiness. How large their impact is on surface temperature and possibly on precipitation due to the cloud modifications is unclear,”

Clouds — even contrails-caused clouds, have also a cooling effect as they “shade” the Earth by blocking and reflecting outward some of the sun’s incoming energy.

June 28, 2019 7:27 am

Greenhouse gases added to the atmosphere above the tropopause (nominally 36,000 feet) actually cool the Earth since temperature there increases with altitude. Fly higher!

Reply to  tty
June 28, 2019 2:12 pm

Science : Aircraft wreak havoc on ozone layer
15 February 1997
By Fred Pearce

“Three years ago Fahey sent a research plane to chase Concorde as it flew high
over the ocean near New Zealand, sampling exhaust gases in Concorde’s slipstream
10 minutes after the supersonic airliner had passed. He discovered much more
sulphuric acid, in the form of a very fine aerosol, than expected. And, using a
model of atmospheric chemistry developed by fellow researcher Bernd Kärcher
of the University of Munich, Fahey has shown how Concorde’s exhaust produces so
many particles.”

John Smith
June 28, 2019 8:05 am

According to NASA data the Earth’s libido has been increasing, contrails or no contrails.

Reply to  John Smith
June 28, 2019 12:30 pm

Do you mean ‘albedo’? Or do you know something about Earth the rest of us don’t?

Joel Snider
June 28, 2019 8:19 am

2050 – just outside of the ‘day after tomorrow’ range.

How many times have they run this shell-game?

June 28, 2019 8:38 am

How will this be an issue in 2050 when everyone is “carbon neutered” by then?

June 28, 2019 8:40 am

Funny how “man made clouds” aka contrails are warming the planet, while natural clouds are cooling it???

Closer to the truth: yes, contrails are warming and likely by a much higher margin than indicated, but natural clouds are doing so even more. And that is the point that kills the GHE due to GHGs.

June 28, 2019 8:41 am

Hmm, so will this be used as an excuse to severely restrict air travel by the masses? Will the determination be made that only the so-called Climaterati and their patrons will be allowed to use air travel?

I expect to hear just such a proposal in 3…2…1….

June 28, 2019 8:42 am

It probably matters a tiny little bit what season the contrail happens in…in the winter, it is probably a cause of some slight warming, especially in the far northern latitudes as the water vapor delays some outgoing IR warmth, and in the summer is probably a net cooling, with some minor reflection of incoming solar. Maybe it’s a wash at the end of the year, I don’t really know. But I would assume there is some effect from the contrail in the atmosphere, but how much should probably be better formulated.

Russ R.
June 28, 2019 8:44 am

So their basic claim is that it is hotter when we create more clouds, than it would be with less clouds??
Which translates to it is hotter in the shade than in the direct sunlight??
Which means that we should be able to compare places of equal latitude which will have equal energy from the sun shining on them. Those with more cloud cover, will be hotter than those with less cloud cover.
So Atlanta, GA is hotter than Phoenix AZ ??

I don’t doubt that Cirrus clouds could have a net warming effect. I do doubt that it is statistically significant enough to extrapolate a small effect far into the future, with all other known and unknown variables remaining static. This is the scientific equivalent of astrology. Pick a few isolated bits of data you like, and ignore the ones you don’t. Make a prediction that will not occur until the astrologer is long gone, with your money.

June 28, 2019 9:21 am

Any pretence to accurate or careful science is not relevant to these people. Only anything that suppports the ‘Cause’ is to be permitted. The aim is to create an Elite entitled to Air Travel, affordable electricity, car transport, cheap food and political status, etc.. As for the rest of the population, they can eat the grass as far as these people are concerned just as their masters in the Soviet Union believed.

Mišo Alkalaj
June 28, 2019 10:54 am

Be in awe of contemporary politicalized science! Observe how a little judiciously applied ignorance (i.e., ignoring the reflected radiation of the Sun) turns what was observed, modeled and measured on its head: namely, that more clouds cause a cooler climate.

And more: the authors Lisa Bock and Ulrike Burkhardt’s future research funding will be positively affected by the impact factor of 5,5 (of the magazine), they will therefore receive more state funding for their break-through research, and publish more articles like this.

Peer review? Gimme a break – it is their colleagues with equivalent interests who reviewed the article.

June 28, 2019 11:19 am

Contrails contribute to pretty sunsets:

Steve Z
June 28, 2019 4:34 pm

[According to the article]”Another often discussed mitigation method is rerouting flights to avoid regions particularly sensitive to the effects of contrail formation.”

Airplane contrails only form when there are light winds at the plane’s altitude in an otherwise clear sky (usually near the center of an anticyclone), otherwise the water droplets from the plane’s exhaust are scattered by the wind before they can form clouds.

Re-routing flights away from zones of clear sky and light winds would force them into areas with strong winds. Planes sometimes ride the jet stream if it produces a tailwind over the planned route, but flight planners usually try to avoid strong headwinds or crosswinds which would increase airspeed and fuel consumption (and water and CO2 emissions) for the same ground speed.

Ask any pilot whether he would prefer flying through turbulence and/or storms, or straight across an area of clear skies and light winds, and the pilot will choose the clear area every time. It’s safer, and it saves time and fuel.

June 28, 2019 6:53 pm

When I was a toddler growing up here in Perth, Western Australia, during the 1960s, I recall looking in awe at the jet contrails that would occasionally be visible in the sky. There weren’t many jets up there compared to nowadays.

Since the 1960s, I pretty well never see jet contrails. In fact, it’s been decades since I saw a contrail over Perth, no matter the month so I assume air temperature isn’t contributing. Whenever I’ve traveled to the east of Australia, same thing. However, when I’ve traveled to the northern hemisphere, and from what I constantly see on American and European television footage, the sky is frequently zig-zagged with contrails. A quick search of the web confirms that many other people have observed that contrails hardly ever happen in Australia but are abundant in the northern hemisphere.

Maybe jets fly at lower altitudes over Australia because of the lack of tall mountains. The reason for our lack of contrails has long puzzled me. Whatever, their absence suggests Australian temperature trends aren’t influenced by contrails – although they are influenced by some very dubious homogenising techniques typified by ACORN 2.

Gary Mount
June 28, 2019 8:11 pm

If I understand correctly this paper is saying that the greenhouse gas water vapor that is already present in the airplanes flight path, when changed to ice crystals, causes a radiative forcing increase. What is the calculated direct or immediate radiative forcing difference?

June 29, 2019 3:10 am

“There’s a new fear of flying: You’re more likely to die from exposure to toxic pollutants in plane exhaust than in a plane crash, a new study suggests.
In recent years, airplane crashes have killed about a thousand people annually, whereas plane emissions kill about ten thousand people each year, researchers say.”

June 29, 2019 6:16 am

Contrail cirrus change global cloudiness, which creates an imbalance in the Earth’s radiation budget – called ‘radiative forcing’ – that results in warming of the planet.

No. The imbalance clouds cause is called ALBEDO.
It cools the planet.
This fraudulent idiocy is not even aimed at scientists.
It’s aimed over their heads at the uneducated and gullible general public.
So now, clouds cause warming even in summer?
Let’s hope for some blue skies so we can cool off from this heat-wave! (Sarc.)

Reply to  Phil Salmon
June 29, 2019 2:21 pm

Phil Salmon, Don’t forget that clouds can act like a blanket at night .

Johann Wundersamer
July 3, 2019 12:30 am

Anthony Watts / 5 days ago June 27, 2019


Jet contrails will likely affect climate by 2050.

Since Jet contrails are produced by Earth’s inheritant fuels here’s no change to Earth’s energy budget.

So what changes every day is Weather.

Not climate.

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