INTERVIEW: Climate change-fueled air turbulence set to hike jet fuel demand: scientist By Frank Watson | Edited by Jonathan Fox | S&P Global Platts | 28 July 2021 * More severe turbulence to prompt airlines to divert routes * Changes in jet stream increasing round-trip journeys * Route deviations waste up to 160 million gallons/year of jet fuel Climate change is expected to drive an increase in the severity of air turbulence which could boost demand for jet fuel in the aviation sector as well as sustainable aviation fuels and carbon credits, an atmospheric scientist said July 28. Paul Williams -- a professor of atmospheric science at the University of Reading, UK -- said the health and safety aspect of severe air turbulence is likely to force airline operators to divert routes to avoid the problem, adding to journey times and fuel burn. "Clear-air turbulence is linked to the jet stream - a natural phenomenon. It's always been there, but it's getting stronger in a very particular way," Williams said in an interview with S&P Global Platts. "The vertical wind shear at aircraft cruising altitudes is expected to strengthen as a result of anthropogenic climate change," he said. Vertical wind shear refers to a change in wind speed or direction with a change in altitude. At moderate levels, this can mean a bumpy ride for passengers. At more severe levels, airlines need to divert routes. WASTED FUEL Changes in wind shear have already been observed over several decades, he said. "The shear has increased by 15% since satellites started measuring the jet stream in the 1970s," he said. "It is said that up to two thirds of flights currently make a diversion due to some turbulence." This averages out at 41 minutes of extra flight-time per deviation. "These deviations waste fuel -- up to 160 million gallons annually -- and they also contribute to climate change through 1.5 million mt of unnecessary CO2 emissions annually," he said. Williams -- an expert in fluid dynamics, climate change and computational modelling -- developed an aviation turbulence forecasting algorithm that is now being used operationally by the US National Weather Service, allowing pilots, aircraft dispatchers and air traffic controllers to conduct their flight planning work more effectively. "Our projections indicate that the airspace volume containing clear-air turbulence will double or treble in the coming decades," he said. "It certainly follows that there will be an increase in the fraction of flights having to divert around turbulence, rather than follow the most fuel-efficient route." Severe natural phenomena can cause widespread disruption to aviation activity, with obvious negative fuel demand impacts. For example, Iceland's Eyjafjallajokull volcano erupted in 2010, grounding 95,000 flights across Europe and the Atlantic for almost a week and causing a $1.7 billion loss for the airline industry. However, such rare events are distinct from long-term changes to air turbulence linked to climate change, and the net result is likely to be positive for fuel demand, Williams said. "Grounding flights would be extreme, but if turbulence is forecasted, the options for airlines are to fly below, above, or around the problem," he said. "Either way, you have to increase fuel burn to drop and then regain altitude, or to re-route your flight," he said. LONGER JOURNEYS While increased tailwind speeds can speed up a flight and reduce fuel burn, the net result of greater turbulence for a round-trip flight is increased fuel demand, he said. "Round trip journeys get longer as the jet stream gets stronger," he said. The net result of increased air turbulence suggests the long-term implication of climate change for the aviation sector is increased fuel burn. While this most obviously impacts traditional jet kerosene demand, a longer-term shift to cleaner aviation fuels also means the turbulence issue could have more widespread impacts for related commodities. Shifts in consumer preferences, national and regional climate regulations and global sector-wide approaches to sustainability all point to long-term shifts in the fuels used to carry people and goods by air, with scope for continued demand growth for sustainable aviation fuel and carbon offset credits. Under the United Nations Carbon Offsetting and Reduction Scheme for International Aviation, airlines are required to buy offset credits to match any CO2 emissions growth above a 2019 baseline. The sector's emissions output tanked due to the pandemic lockdowns in 2020 but emissions are expected to rebound as restrictions ease. Carbon offset credit prices have already shown a rising trend in 2021, with CORSIA-eligible carbon (CEC) credit prices rising from 80 cents/mt in January to $3.06/mt on July 27, according to S&P Global Platts assessments -- reflecting growing corporate demand as companies seek to hit long-term net-zero emissions targets. And in conventional jet markets, refining margins are finally seeing support from jet fuel demand growth, an analysis from S&P Global Platts showed June 1, with travelers taking to the sky amid increasing coronavirus vaccinations after prolonged lockdowns. Despite jet fuel demand rebounding from 2020 lows, demand is still somewhat below pre-COVID levels. US jet fuel demand, for example, averaged 1.2 million b/d in the first half of 2021, up from 1.1 million b/d in 2020 but below 2019 consumption of 1.7 million b/d, the US Energy Information Administration said in figures updated July 7. The EIA expects jet fuel consumption will average 1.4 million b/d in 2021, rising to 1.7 million b/d in 2022, it said.