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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.
Contrail cirrus radiative forcing for future air traffic (DOI: 10.5194/acp-19-8163-2019)
(Score: 4, Interesting) by AthanasiusKircher on Friday June 28 2019, @11:27PM (1 child)
Just a clarification: that link says that the daily SWING of temperatures was reduced by 5-6 degrees F, not the daily high temp. Presumably the highs were lowered by 2-3 degrees and the loss were raised by 2-3 degrees. Not a very big effect, but still interesting.
I would imagine the overall long-term heating effect comes from the fact that water vapor is one of the most substantial greenhouse gases in the atmosphere. Increasing the quantity of it will hold heat in and prevent thermal radiation to space. Yes, it also can help reflect heat a bit in clouds, but once the heat gets in, water vapor will keep it bouncing back down to the ground, so anything that adds significant quantities of water vapor to the atmosphere will contribute to greenhouse effects.
(Score: 3, Interesting) by bradley13 on Saturday June 29 2019, @05:35AM
As I understand it, it isn't so much the visible contrails, but rather the water vapor released by burning fuel is acting as a greenhouse gas, and producing the warming. Water vapor is a potent greenhouse gas.
The thing is, as with so many of these models, they don't seem to consider negative feedback. If the atmosphere were subject to runaway effects based on either CO2 or water, it would have already run away. If you release more water into the atmosphere, all that's going to happen (in anything beyond the short term) is that it will condense and rain out.
The entire AGW argument is based on positive feedback: CO2 (which is a very minor greenhouse gas) raises the atmospheric temperature, which therefore allows more water vapor to remain in the atmosphere, which raises the temperature, which allows more water vapor... That isn't how things work. Failure to account for negative feedback is the reason why all of the long-term climate models keep missing their predictions [duckduckgo.com].
Which is not to say that dumping piles of CO2 into the atmosphere is a good idea. We only have the one atmosphere, and carrying out uncontrolled experiments on it is not a great idea. But the continuous alarmism (of which TFA is just the latest example) is tiresome, and imho gets in the way of doing actual, good science.
Everyone is somebody else's weirdo.