OCT 2, 2017 ETHAN COFFEL
Our infrastructure is designed for the climate in which it was developed; engineering standards and logistical procedures are based on historical weather patterns, and as environmental conditions change, some of these systems may need to be re-configured.
In aviation, aircraft takeoff performance depends on temperature. This is because in the atmosphere, temperature is the key determinant of air density, which in turn affects the amount of lift that an airplane wing generates at a given speed. Pilots refer to this as the “density altitude”, a metric indicating the elevation that would produce a given air density if the temperature was 15°C (standard meteorological conditions). For instance, an airport might be located at a true altitude of 100 feet, but on a very hot day could have a density altitude of 1,000 feet, indicating that the air is less dense because of the heat.
Density altitude is essential in takeoff performance calculations as it determines the airplane’s required takeoff speed. At lower density altitudes, a wing produces less lift, all things equal, and so must travel faster to fly. If the required takeoff speed is high enough, there may not be enough runway available for the aircraft to accelerate; the only option then is to reduce the airplane’s weight, likely by removing payload – passengers and cargo. This is referred to as a “weight restriction”.
The 1°C or so of warming that the earth has experienced since pre-industrial times has already raised the average density altitude by about 100 feet. Future climate change will raise density altitudes further, likely by several hundred more feet. This will make weight restrictions more common, with potentially non-trivial impacts on the payload capacity of airplanes worldwide.
Research that I’ve recently conducted along with Dr. Terry Thompson and Dr. Radley Horton (see here and here) , suggests that by the second half of the 21st century, 10 – 30% of commercial flights taking off near their current maximum takeoff weights (as a long-haul flight often does) could require at least some weight restriction; this in turn comes with overall payload reductions of up to 0.5% as compared to a world with no warming. The small percentage change may sound insignificant, but even minor changes in weight can have large costs both in increased fuel consumption and reduced passenger load when spread across an airline’s fleet. To put this in context, a 0.5% payload reduction adds up to as much as 18 million passengers per year globally at today’s traffic levels.
Weight restriction is just one of several impacts of climate change on the aviation industry. Work by Dr. Paul Williams has shown that turbulence associated with high altitude winds may increase in frequency and intensity due to a strengthening jet stream (see research here and here) , and sea-level rise may damage coastal airports like New York’s LaGuardia or San Francisco International. In addition, amplified heat stress may make it dangerous for people to work outside in some regions, meaning that airport ramp workers will need more frequent breaks and other precautions to avoid severely reduced productivity and potential heat illness.
Most industries face future climate risks to their infrastructure or resource supplies, and most of that risk has not been thoroughly explored or quantified. An enormous amount of work will be needed to adapt our infrastructure and modify our logistical procedures to better prepare for future heat, storms, and sea levels. The sooner this work begins, the more effective adaptation can be; without planning, less hospitable climate conditions will impose higher costs on industries, and increasingly frequent natural disasters will be more damaging and harder to recover from.
Of course, we must keep the focus on why we have this issue in the first place – exponentially growing greenhouse gas emissions. Adaptation strategies help us cope with climate impacts that are already in motion, but we must also tackle the root cause of the problem by rapidly reducing fossil fuel consumption, deforestation, and other drivers of climate change. If we fail to avert the worst climate outcomes, we risk spending an increasing percentage of our economic output and societal wealth and energy dealing with the new climate that we’ve created. The costs will come from large natural disasters like Hurricane Harvey, but also from the need to re-engineer and redesign procedures for modified weather patterns, protect infrastructure from sea level rise, and account for the reduced economic performance associated with higher temperatures. Perhaps a better understanding of the costs of climate change will encourage us to work to prevent these worst-case scenarios before they become a reality that we have to adapt to.References:
Coffel, E. D., Thompson, T. R. & Horton, R. M. The impacts of rising temperatures on aircraft takeoff performance. Climatic Change 1–8 (2017). doi:10.1007/s10584-017-2018-9
Coffel, E. & Horton, R. Climate Change and the Impact of Extreme Temperatures on Aviation. Weather. Clim. Soc. 7, 94–102 (2015).
Williams, P. D. Increased light, moderate, and severe clear-air turbulence in response to climate change. Adv. Atmos. Sci. 34, 576–586 (2017).
Williams, P. D. & Joshi, M. M. Intensification of winter transatlantic aviation turbulence in response to climate change. Nat. Clim. Chang. 3, 644–648 (2013).
Kjellstrom, T., Kovats, R. S., Lloyd, S. J., Holt, T. & Tol, R. S. J. The Direct Impact of Climate Change on Regional Labor Productivity. Arch. Environ. Occup. Health 64, 217–227 (2009).
Burke, M., Hsiang, S. M. & Miguel, E. Global non-linear effect of temperature on economic production. Nature 527, 235–239 (2015).