Hot weather has forced dozens of commercial flights to be canceled at airports in the Southwest this summer. This flight-disrupting heat is a warning sign. Climate change is projected to have far-reaching repercussions - including sea level rise inundating cities and shifting weather patterns causing long-term declines in agricultural yields. And there is evidence that it is beginning to affect the takeoff performance of commercial aircraft, with potential effects on airline costs.
National and global transportation systems and the economic activity they support have been optimized for the climate in which it all developed: Machines are designed to operate in common temperature ranges, logistical plans depend on historical weather patterns and coastal land development is based on known flood zones. In the aviation sector, airports and aircraft are designed for the weather conditions experienced historically. Because the climate is changing, even fundamental infrastructure elements like airports and key economic sectors like air transportation may need to be redesigned and reengineered.
As scientists focused on the impacts of climate change and extreme weather on human society and natural ecosystems around the world, our research has quantified how extreme heat associated with our warming climate may affect flights around the world. We've found that major airports from New York to Dubai to Bangkok will see more frequent takeoff weight restrictions in the coming decades due to increasingly common hot temperatures. There is evidence that extreme events such as heat waves and coastal flooding are happening with greater frequency than a few decades ago. And if we fail to reduce greenhouse gas emissions significantly, the frequency and intensity of these extremes is projected to increase dramatically.
The effects on aviation may be widespread. Many airports are built near sea level, putting them at risk of frequent flooding. The frequency and intensity of air turbulence may increase due to high-altitude winds. Stronger winds would force airlines and pilots to modify flight lengths and routings, potentially increasing fuel consumption.
The July heat-related Phoenix flight cancellations happened at least in part because airlines' operational manuals didn't include information for temperatures above 118 degrees Fahrenheit - because that kind of heat is historically uncommon. It's another example of how procedures may need to be updated to adapt to a warmer climate. High air temperatures affect the physics of how aircraft fly, meaning aircraft performance can be impaired on hot days. The amount of lift that an airplane wing generates is affected by air density which in turn depends on air temperature and elevation
On most affected flights, the amount of cargo, passengers and fuel that must be removed to allow for takeoff will usually be small - between 0.5-4% of the total load. That means fewer paying customers on airplanes, and less cargo on board. When those restrictions add up across the global air transport system, the costs can be significant.
The lower the air density, the faster an airplane must travel to produce enough lift to take off. This takes more runway Some airplanes might risk running out of room before reaching sufficient speed. When this occurs, the only immediate option is to reduce the aircraft's weight - by removing passengers, luggage and cargo. This is referred to as a weight restriction.
Weight restrictions happen now, especially in hot places like Phoenix and Dubai and at airports with short runways like LaGuardia and Reagan National.
Global temperatures have been rising for decades, and will certainly continue to do so. In some regions, there is evidence that the hottest temperatures may increase at a faster rate than average, further stacking the deck. These hotter temperatures will reduce air density and make it much more likely weight restrictions are needed for flights taking off during the hottest parts of the day.
Carrying just a fraction of a percent fewer passengers or less cargo can add up to millions of dollars in lost revenue for an airline. That makes even small weight restrictions a concern.
There are ways that airlines could mitigate increasing weight restrictions. The most feasible is to reschedule flights to cooler hours of the day - although, this could prove difficult.
Another potential solution is to build longer runways. But that's not always possible: Some airports are on coastlines or in dense urban environments. Even where a longer runway is technically possible, buying land and expanding an airport's physical area may be expensive and difficult.
Aircraft could be optimized, but redesigning is extremely expensive. Manufacturers are always working to build planes that are lighter and more fuel-efficient. In the future, those efficiency improvements will be necessary just to maintain today's performance.
Many sectors of the economy, including the aviation industry, have yet to seriously consider the effects of climate change. The sooner, the better: Both airport construction and aircraft design take decades, and have lasting effects. Today's newest planes may well be flying in 40 or 50 years, and their replacements are being designed now. The earlier climate impacts are understood and appreciated, the more effective and less costly adaptations can be. Those adaptations may even include innovative ways to dramatically reduce climate-altering emissions across the aviation sector, which would help reduce the problem while also responding to it.
