A Small Change in Airplane Altitude Could Reduce Climate Impact of Contrails by 59%

In a world affected by climate change, every little tweak we make counts. While we’re still sorting out jet fuel, there’s another plane travel impact we could cut back on rather easily, according to a new study.

Getting planes to fly just 2,000 feet (610 metres) lower could cut the climate impact of the contrails they leave behind by a whopping 59 percent.

Even better, only around 2 percent of flights would need to make the adjustment – those flights where contrails are most likely to form, linger around, and contribute to the warming of the planet.

Contrails (condensation trails) come about when the hot exhaust gas from airplanes meets the cold, low-pressure air in the atmosphere. Moisture condenses on the black carbon in the fumes, forming the ice particles we see as white streaks in the sky.

While most contrails vanish in minutes, some can stick around for up to 18 hours, mixing with other contrails and cirrus clouds. This forms ‘contrail cirrus’, which shifts the temperature balance of Earth through what’s known as radiative forcing.

This radiative forcing happens when contrails reflect incoming shortwave radiation back out to space, while trapping longwave infrared radiation on Earth, causing a warming effect.

“According to our study, changing the altitude of a small number of flights could significantly reduce the climate effects of aviation contrails,” says civil engineer Marc Stettler, from Imperial College London in the UK. “This new method could very quickly reduce the overall climate impact of the aviation industry.

“A really small proportion of flights are responsible for the vast majority of contrail climate impact, meaning we can focus our attention on them.”

Studies suggest that contrails and radiative forcing could be heating up the planet as much as CO2 emissions from aircraft fuel, but the impact of contrails is much more short-lived – and potentially easier to tackle.

The researchers analysed data from Japanese airspace over the course of six weeks, running models with planes flying either 2,000 feet higher or 2,000 feet lower than their actual flight paths. With 1.7 percent of flights flying lower, the data showed, a cut in contrail climate forcing of 59 percent could be achieved.

Some extra fuel would be consumed along the way, but this would be offset by reduced contrail formation and the warming it produces, the study shows.

Add the widespread adoption of cleaner jet engine fuel to the altitude adjustments, the researchers say, and the contribution of contrails to climate change could drop by up to 90 percent. However, with so many variables at play, further research on a wider dataset will be required to know for sure.

What’s clear is that the environmental impact of contrails should not be underestimated: the research shows that they can make a significant contribution to global warming (though you don’t have to worry about a government cover-up).

“Contrail models are vital in validating the effectiveness of different mitigation solutions such as the use of alternative fuels, new engine technology, and flight diversion strategies,” the researchers write in their paper. SOURCE

California is on track to miss its climate targets—by a century

And it’s likely to get harder, not easier, for the state to achieve ever deeper cuts in emissions

AP / NOAH BERGER

California has established itself as a global model on climate issues, with Teslas filling its roads and solar farms stretching across its sun-baked Central Valley.

The state set up the nation’s first economy-wide cap-and-trade program, put in place aggressive vehicle fuel efficiency standards, and passed a series of ever stricter climate pollution rules. That includes the landmark 2018 law requiring all of the state’s electricity to come from carbon-free sources by the end of 2045.

But for all its regulatory achievements, California also offers a case study in just how hard it is to make progress on the only thing that really matters: reducing emissions.

The state’s climate pollution declined by just 1.15% in 2017, according to the latest California Green Innovation Index. At that rate, California won’t reach its 2030 decarbonization goals (cutting emissions to 40% below 1990 levels) until 2061—and wouldn’t hit its 2050 targets (80% below 1990 levels) until 2157.

If a state that’s actively trying to slash emissions is on pace to miss its targets by a century, that bodes poorly for progress in the many other parts of the world that are barely bothering. Crucially, the UN’s climate panel says the world as a whole needs to achieve “net zero” emissions by 2050 to halt warming at 1.5 ˚C, or by 2070 to stay below 2˚ C.

What went wrong?

Transportation emissions, the state’s largest source, have steadily risen since 2013, as the improving economy put more cars on the road and planes in the sky. Emissions from waste dumped into landfills have also been ticking up since the recovery took hold. Meanwhile, highly potent greenhouse gases from the aerosols, foams, and solvents used in refrigeration and air conditioning are rising sharply.

These increases have offset the highly touted declines in emissions from the electricity sector as a growing share of the state’s power comes from renewable sources like wind and solar. Emissions from in-state generation are down 35% since 2000.

The new math means California will now need to boost its annual emissions cuts to 4.51% per year to pull off its 2030 targets—or 5.34% annually to achieve its 2050 goals, the report found. And of course, every year the state comes in below those rates will only push those numbers even higher.

The problem is it’s likely to get harder, not easier, for California to achieve ever deeper cuts in emissions. To understand why, consider three areas:

Slowing progress for renewables

Electricity is actually the easy part of decarbonization, because we have relatively cheap and reliable wind, solar, geothermal, and other carbon-free sources. But new renewables projects commissioned by the state’s investor-owned utilities, like PG&E and SDG&E, have been nearly flat for the last three years.

The report says that’s mainly because utilities had already achieved the state’s 2020 renewables targets years early—indeed, they’re way ahead.

But energy observers stress that deeper, systemic problems are building: the state’s utilities are losing loads of customers to community choice aggregators. These programs allow local communities, like Marin and Berkeley, to buy electricity from in-state or out-of-state sources on behalf of their residents and businesses, but still lean on the utility’s transmission and distribution infrastructure.

That’s left utilities with more power plants than they need, and thus no reason to enter into additional deals with developers to build renewables facilities. In fact, they could go deep into the next decade without adding contracts for new solar or wind farms and remain in compliance with the state’s tightening renewables standards, says Matthew Freedman, staff attorney with the Utility Reform Network, a consumer advocacy group, and a lecturer at the UC Berkeley School of Law.

Bottom line: It could take years before the state starts to see a real uptick in new renewables projects again. Recognizing the growing challenges presented by this fragmentation of the state’s energy system, some California legislators have proposed tasking a state agency with ensuring the necessary levels of clean electricity development.

Hard-to-solve sectors

Achieving deeper cuts in other areas is even harder.

The glimmer of good news for transportation is that electric vehicles do represent a growing share of new vehicle sales, at just under 8% in the state last year. But they still make up only 1.5% of registered vehicles in the state, with hybrids accounting for 3.4%, the report notes.

At the same time, overall car ownership rates are rising, public-transit use is falling, and consumers are still shifting toward gas-guzzling trucks and SUVs. And the 92% of vehicles sold last year that weren’t EVs will, on average, still be on the roads more than a decade from now.

Accelerating the shift to cleaner vehicles is likely to require far stricter policies, far more generous subsidies, cheaper EVs, and a massive build-out of charging infrastructure. And even California’s efforts to boost the average fuel efficiency of cars sold in the state have been complicated by the Trump administration’s legal challenges.

California has created some novel programs to help cut emissions in other areas, including agriculture. But there simply aren’t available technologies yet to fully decarbonize some of the state’s emission sources, including aviation.

Wildfires

Finally, California’s worsening wildfires are also complicating its efforts to cut emissions. Burning forests pump out massive amounts of greenhouse gases stored in plants and trees. And rising temperatures and shifting precipitation patterns have already extended the fire season by 75 days across the state’s sprawling Sierra Nevada range.

The raging wildfires in 2018 produced about 45 million metric tons of carbon dioxide. That’s nine times more than the amount by which the state cut emissions the previous year. SOURCE

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