Many of the impacts of global warming are disproportionately going to impact the poor globally. But there’s one that even the global rich will have trouble dodging: clear-air turbulence while flying.
This isn’t flying through or around thunderstorms, where some bumpiness is to be expected, but something that happens well above whatever clouds exist in clear air. Sudden downdrafts, updrafts, and side drafts that are invisible to the human eye can cause serious challenges for aircraft that fly through them. People have died due to clear-air turbulence.
The US FAA, which analyzes and reports on air traffic safety, says that from “1980 through 2008, U.S. air carriers had 234 turbulence accidents, resulting in 298 serious injuries and three fatalities.”
There have been projections published in recent years that global warming would cause more of the wind shear which creates clear-air turbulence, and as a result cause more incidents in the global web of passenger jets that circle the world. However, these were more modeled than observed. Until now.
A study published in early August 2019 in Nature (yes, a very high credibility journal with good peer-review filters), Increased shear in the North Atlantic upper-level jet stream over the past four decades, by Simon H. Lee, Paul D. Williams, and Thomas H. A. Frame, all from the University of Reading, UK showed increased vertical shear.
“… vertical shear has increased by 15 per cent (with a range of 11–17 per cent) according to three different reanalysis datasets15,16,17. […] The increased vertical shear is consistent with the intensification of shear-driven clear-air turbulence expected from climate change which will affect aviation in the busy transatlantic flight corridor by creating a more turbulent flying environment for aircraft.”
Their finding was that the traditional measure used was masking already existing increases in a different measure, similar to how the Saffir-Simpson and Accumulated Cyclone Energy scales don’t account for climate-change induced increases in storm diameter, rainfall, and storm surge. It also appears to be related to why the two primary hurricane scales have not been showing increases in terms of wind velocity and frequency of severity in the North Atlantic as has been observed in the Pacific already.
However, the study didn’t correlate this observation to passenger plane routes except in the most general way, nor did it attempt to correlate it to any records on clear air turbulence. Despite some other headlines which somewhat overstated the results, this isn’t a case of a smoking gun for an already existing impact.
I reached out to Professor Paul Williams of Reading University in the UK, co-author of several papers in this space, for his insights on whether any incidents of significant clear-air turbulence impacting passenger planes had been identified, or even could be.
“Attribution studies, to identify the fingerprints of climate change in specific clear-air turbulence encounters, have not yet been carried out. It will always be a scientific impossibility to state that a particular turbulence encounter was caused by climate change. However, with further research, we may soon be able to state that a particular encounter was, for example, made twice as likely by climate change. We can already do that for heatwave events, and it is only a matter of time before the same methodology is applied to turbulence events.” – Paul D. Williams
It does, however, lend credibility to previous studies which predicted increased turbulence. One of the same authors was involved in a previous study, published in 2017 in the American Geophysical Union journal (yes, also higher reliability), Global Response of Clear‐Air Turbulence to Climate Change, by Luke N. Storer, Paul D. Williams, and Manoj M. Joshi.
“… changes to clear‐air turbulence over the entire globe by the second half of this century. We consider eight geographic regions, two flight levels, five turbulence strength categories, and all four seasons. We find strong increases in clear‐air turbulence over the entire globe and in particular the midlatitudes, which is where the busiest flight routes are. We also find that the strongest turbulence will increase the most, highlighting the importance of improving turbulence forecasts and flight planning to limit discomfort and injuries to passengers and crew.”
The bolding is mine to indicate that this is not a general background increase, but specifically an increase in the kind of turbulence which causes injuries.
Some of the solutions to this problem are pointed out. Improving turbulence forecasts and adjusting routes will limit this somewhat, but airplanes will be seeing a double-impact in terms of costs. By 2050, it’s likely that they will be required by either mandate or carbon-pricing to use much-lower carbon biofuels or synthetic fuels that are also more expensive. If they are then required to take longer routes or fly at less efficient altitudes, this will compound the fuel cost impacts.
Plane-based clear-air turbulence detection technologies have been being studied for at least two decades. The obvious candidates are Doppler radar systems and Lidar. Both of these systems become expensive when the range and sensitivity required for distant detection of clear-air turbulence allowing smooth flight path responses are considered. The Lidar system under assessment by Boeing and others would give only 70 seconds advance notice, allowing mitigation of some but not all concerns.
What this really all means is that we’ll start seeing specific large-impact clear-air turbulence incidents attributed in part to climate change in the coming years, that some regions of the globe will have worse impacts than others, that newer planes will be better able to ride it out, and that you should really heed the seatbelt warnings on your flights.
And of course, that the people who fly the most, the global 1%, will have a global warming impact that they can’t just fly away from.
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