Clear-Air Turbulence Is Getting Worse—And Climate Change May Be to Blame

Redacción HC
29/11/2023

For decades, airline passengers have grown accustomed to the occasional jolt mid-flight—unsettling but often brief. But what if those bumps in the sky are not just random turbulence, but a symptom of a changing planet? A new study published in Geophysical Research Letters reveals compelling evidence that clear-air turbulence (CAT)—the invisible, unpredictable kind that occurs in cloudless skies—has significantly increased over the past 40 years. The implications extend far beyond discomfort, affecting airline safety, economics, and even climate policy.

A Growing Threat Above the Clouds

Clear-air turbulence is notoriously difficult to detect because it occurs without visual cues like clouds or storms. This phenomenon is caused by wind shear and jet stream instabilities at cruising altitudes, typically around 39,000 feet. While previous research predicted that CAT would intensify with global warming, this new study by Prosser, Williams, Harrison, and Marlton offers the most comprehensive empirical evidence to date confirming that this is already happening.

Using high-resolution ERA5 reanalysis data from 1979 to 2020, the researchers analyzed turbulence levels at flight altitude across the globe. Their central question: Has clear-air turbulence measurably increased over recent decades? The short answer: yes—and by a worrying margin.

The Method Behind the Numbers

To ensure the robustness of their findings, the researchers applied 21 different diagnostic models for CAT across the ERA5 dataset—a cutting-edge atmospheric reconstruction that integrates satellite and in-flight observations. They focused on the 197 hPa pressure level, which corresponds to typical airline cruising altitudes.

For each geographic location, they calculated the annual probability of encountering moderate-or-greater turbulence (MOG) and assessed long-term trends using linear regression. Special attention was given to high-traffic regions like the North Atlantic and continental United States.

The results were statistically significant: most diagnostics revealed strong upward trends, particularly in mid-latitude flight corridors. The study also accounted for potential biases introduced by evolving instrumentation over time—a common concern in long-term climatological reanalysis.

Clearer Skies, Rougher Rides: What the Data Reveals

The findings paint a turbulent picture of our skies. Over the North Atlantic, turbulence has spiked dramatically:

• Light-or-greater CAT increased by 17% (from ~466 to ~547 hours per year).
• Moderate-or-greater CAT rose by 37% (from ~70 to ~96 hours).
• Severe-or-greater CAT jumped by 55%, from ~17 to over 27 hours annually.

Similar upward trends were observed over the United States. These increases are not minor fluctuations but statistically robust patterns indicating a changing atmospheric dynamic.

Crucially, the study compared these results to past climate projections. Models had previously estimated that doubling atmospheric CO₂ could increase CAT by 80%. Since CO₂ levels rose by about 30% between 1979 and 2020, the actual observed CAT increases—especially the 55% surge in severe cases—suggest that climate models may have underestimated the short-term impact.

Sky-High Implications for the Airline Industry

This trend carries significant practical consequences. Clear-air turbulence is not just a nuisance—it’s a safety risk. Severe turbulence can cause serious injuries to passengers and crew, damage aircraft interiors, and even compromise structural integrity.

In the U.S. alone, CAT-related costs—ranging from maintenance and flight delays to emergency diversions—are estimated at $150 to $500 million annually. If severe CAT continues to intensify, these costs could balloon, threatening both the safety and profitability of air travel.

The study underscores the urgency for airlines and aviation regulators to:

• Upgrade turbulence forecasting systems using LIDAR and enhanced modeling.
• Implement real-time detection technologies to reroute flights proactively.
• Promote continuous seatbelt use to protect passengers from sudden jolts.

Turbulence as a Climate Indicator

Beyond its operational consequences, rising CAT serves as a canary in the coal mine for broader climate dynamics. As greenhouse gas emissions warm the planet, atmospheric instability is increasing, particularly in the upper troposphere where commercial jets fly.

This is not just theory. The study’s results suggest that the turbulence we feel on flights is a tangible symptom of global climate change. It adds to a growing body of evidence showing that the aviation sector is both a contributor to—and a victim of—climate disruption.

What Comes Next: Policy and Passenger Preparedness

To address these challenges, the authors recommend:

• Enhancing operational forecasts for turbulence with finer spatial and temporal resolution.
• Investigating other turbulence sources, such as mountain-induced or convective turbulence.
• Integrating climate-driven turbulence trends into flight route planning and aircraft design.

For passengers, awareness is key. Keeping seatbelts fastened at all times may soon become more than a precaution—it could be a life-saving habit.

Conclusion: The Invisible Storm in Our Skies

What used to be considered isolated, weather-related turbulence is now increasingly understood as a systemic response to a warming atmosphere. This study offers a wake-up call not only to the aviation industry but also to climate scientists and policymakers. As skies grow rougher in the age of climate change, the path forward will require better forecasting, smarter technology, and a firm commitment to emissions reduction—before turbulence becomes the new normal.

Topics of interest

Climate