Flying often involves encountering atmospheric turbulence, the irregular movement of air that causes an aircraft to bump and shake. While turbulence is a natural part of aviation, scientific data suggests a shift is occurring in the upper atmosphere. Research indicates that the severity and frequency of turbulence, particularly at high cruising altitudes, is on the rise, linked directly to changes in the Earth’s climate system.
The Different Forms of Atmospheric Turbulence
Atmospheric turbulence is the motion of air caused by eddies and vertical currents that disrupt smooth airflow. This disturbance is categorized into three primary types affecting aircraft. Mechanical turbulence occurs when wind flows over obstacles like mountains, creating swirling air patterns close to the ground.
Thermal turbulence, also known as convective turbulence, arises from uneven solar heating of the Earth’s surface. Warm pockets of air rise rapidly through cooler air, leading to vertical currents. The third type is dynamic turbulence, generated by wind shear—a sudden, significant change in wind speed or direction over a short distance. This wind shear is potent at high altitudes, especially near the jet stream.
How Climate Change Intensifies Wind Shear
The primary driver behind worsening turbulence is the alteration of global atmospheric circulation patterns due to rising temperatures. The powerful jet stream, a fast-moving ribbon of air at cruising altitudes, is normally powered by the strong temperature difference between the warm equator and the cold poles. This difference, known as the meridional temperature gradient, dictates the jet stream’s speed and stability.
The Arctic region is warming significantly faster than the rest of the globe, a process called Arctic amplification. This disproportionate warming reduces the temperature contrast between the North Pole and the equator. A weaker temperature gradient leads to a less stable and wavier jet stream, causing it to slow down and meander.
These changes translate directly into an increase in wind shear. The wavier path of the jet stream creates sharper gradients in wind speed and direction across the atmosphere. Studies show that vertical wind shear, which measures how wind speed changes with altitude, has already increased over the past four decades. This enhanced wind shear creates more severe atmospheric disruptions, making the high-altitude air more turbulent.
Climate models project that vertical wind shear will continue to increase, potentially rising by 16% to 27% between 2015 and 2100. The atmosphere is becoming less stable, setting the stage for more frequent and intense turbulence events. This destabilization is a direct consequence of changing temperature dynamics driven by global warming.
The Growing Challenge of Clear-Air Turbulence
The intensification of wind shear is linked to the increase in Clear-Air Turbulence (CAT), a unique and growing challenge for aviation. CAT is severe, invisible turbulence that occurs in cloudless skies, typically near the jet stream at altitudes above 15,000 feet. The heightened wind shear directly leads to more frequent and stronger CAT events.
On busy flight corridors like the North Atlantic, the annual duration of severe turbulence increased by as much as 55% between 1979 and 2020. This turbulence is problematic because conventional weather radar systems, designed to detect precipitation, cannot identify it. Since the air is clear, pilots often encounter CAT suddenly without visual warning or the ability to provide adequate passenger notification.
The unpredictability of CAT is a safety concern, as it can toss an aircraft violently, leading to serious injuries for unfastened passengers and crew. The growing frequency of severe CAT requires pilots to rely on real-time reports from other aircraft and advanced forecasting systems. As the climate continues to warm, the challenge of detecting and avoiding this invisible phenomenon will become more pronounced for the aviation industry.