Story ID: 
Researchers Tackle Tradeoffs in Aviation’s Climate Impact
By: Hanneke Weitering
Caption: Simply reducing aircraft fuel burn is not necessarily the greenest strategy
Word Count: 379
To help the aviation industry reduce its climate impact, researchers at the University of California, Irvine, have developed a tool that they claim will enable operators to make smarter flight decisions.
In the sector’s quest to curb its contributions to global warming, aircraft operators and manufacturers have consistently focused their efforts on reducing carbon dioxide (CO2) emissions, as well as nitrogen oxides (NOx) and contrails that trap heat in Earth’s atmosphere.
Eco-conscious aircraft operators seeking to minimize their climate footprint often have tradeoffs to consider. For example, they can reroute a flight to avoid atmospheric conditions conducive to contrail formation, but that might increase fuel burn and emissions.
A team of researchers led by Michael Prather, a professor of Earth system science at UC Irvine, has created a decision-making tool that assesses the overall climate impact of specific aviation activities (including the production of CO2, NOx, and contrails) and identifies the most climate-friendly course of action.
“Our findings show that we don’t have to choose between reducing carbon emissions and tackling other warming pollutants,” Prather said. “We can find a balance that leads to meaningful progress.”
In calculating how much those activities warm the atmosphere—a measure known as “radiative forcing” (RF)—the model accounts for and quantifies uncertainties in those elements. For example, the RF of a contrail depends on various dynamic conditions and can be difficult to accurately predict or measure. The so-called “global warming per activity” (GWA) tool provides a decision risk curve that shows the probability of a specific tradeoff resulting in a climate benefit.
“We have always tried to build uncertainty quantification into our climate assessments,” Prather said. “But this new decision tool uses the information to provide accurate risk quantification for climate tradeoff decisions.”
Using the GWA, the UC Irvine team determined that increasing fuel burn to avoid producing contrails might be better for the planet than sticking with the most fuel-efficient route. For example, they calculated that a 1% increase in fuel burn that leads to a 4% reduction in contrail RF has a 67% chance of climate mitigation over a 100-year period. The results of the study were published in the journal Nature on July 2.