Flying premium from San Francisco to Los Angeles, a common trip for some Californians, could generate 101 kilograms of carbon emissions, or perhaps 142 or even 366 kilograms—depending on what source you search online.
The wide range of estimates stems from what some climate experts view as a growing problem, with Google at the center. More people are trying to factor climate change impacts into life choices such as where to vacation or what to eat. Yet scientists are still debating how to accurately estimate the impacts of many activities, including flying or producing meat. While the math gets sorted out, some industries decry emissions estimates as unfair.
Google has led the way among big tech companies in trying to inform users about their potential carbon footprint when traveling, heating their homes and, as of recently, making dinner. But airlines, cattle ranchers, and other industry groups are pushing back, saying Google’s nudges could hurt their sales. They have demanded—successfully, in the case of airlines—that the search giant rethink how it calculates and presents emissions data.
The United Nations' climate panel has begun saying individual decisions are significant, noting for instance in a report last year that taking trains and avoiding long flights could account for as much as 40 percent of the potential cut in global aviation emissions by 2050 from changes in how people choose to travel. But for consumers, getting a personal read on their carbon impact is tricky, as major studies tend to focus on global or regional averages and not personalized metrics, emissions researchers say.
Scientists and startups working on emissions estimates worry that showing shoppers varying data will leave them not only misinformed about the impact of their choices but also discouraged from trusting emissions estimates for years to come. That could hamper efforts to slow the release of planet-warming gases.
"It's concerning when there is fragmentation and misalignment," says Sally Davey, chief executive of Travalyst, a nonprofit convening travel players including airlines, Google, Expedia, and Visa to standardize emissions formulas. "If we create noise and not clarity and consistency, people switch off, and we won’t drive the behavior we want."
Google emerged as a potentially powerful force in consumers’ personal climate footprints since publicly setting a goal in September 2020 to help 1 billion people make sustainable choices through its services by the end of 2022. That pledge has led to several new features across Maps, Flights, Search, Nest thermostats, and other Google services, which collectively have more than 3 billion users. Last year brought record high Google searching for “rooftop solar power,” “electric bicycles,” and “electric cars,” according to the company.
Rivals such as Apple, which optimizes iPhone charging based on the mix of energy sources on the local grid, and Microsoft, which highlights eco-friendly shopping items on Bing, have launched "green" features of their own. But no consumer tech company can match the breadth or audience size of Google’s climate features or the granularity of data it pushes at consumers, down to the tenth of a kilogram of emissions in the case of protein sources.
Yet Google’s chief sustainability officer, Kate Brandt, acknowledges that its mission to inform users about less-emissions-intensive choices is a work in progress. "We’re seeing people want information, but they don’t know what are the most meaningful choices they can make," she says. "The data is going to keep changing and getting better. It’s not static." Brandt declines to say whether Google met its goal of helping 1 billion people by the end of 2022 but says the company plans to show its progress in its annual environmental report, which is due middle of this year.
Joro, a startup that offers an app for tracking and offsetting emissions from card purchases, recently reviewed four online calculators for estimating flight emissions to aid consumers. Its analysis, which drew on guidance from academic advisors such as Yale University environmental researcher Reed Miller, revealed big differences on routes including San Francisco to Los Angeles.
The International Civil Aviation Organization (the UN's aviation body) and the international airline trade group IATA offer diverging formulas for calculating aviation emissions, Joro says. The trade group focuses on flight time over distance traveled and uses data from airlines on fuel-burn averages by aircraft and load that are drawn from real flights instead of what the group considers to be less accurate estimates used by other calculators.
Joro also found Google splits with the Swiss nonprofit Myclimate, which consults with companies seeking to tally and mitigate emissions. Unlike the search company, Myclimate incorporates emissions from beginning to end including jet-fuel manufacturing, idling planes at airports, and busing passengers from gates. Myclimate also adds some non-carbon impacts, including the heating effect on the atmosphere of contrails, which are the clouds formed by plane exhaust.
Emissions on the San Francisco route show as 75 to 101 kilograms per first-class passenger on Google. Myclimate suggests 366 on average, the trade group 142, and the UN body 85.
Google has a financial stake in making people comfortable with flying. Google does not charge a commission on flight bookings, but travel and hospitality operations, including airlines, are among the biggest spenders on Google ads, and consumers feeling uncomfortable about traveling because of its contributions to global warming ultimately could slow travel and ad sales.
People find value in seeing emissions data when buying flights and will spend more for a less polluting option, according to a 2021 study by UC Davis researchers who showed people an experience similar to Google Flights. But the completeness of Google’s estimates for individual flights will become more important as people start comparing modes of transport for a potential trip and begin developing an intuition about emissions from different parts of their lives to make trade-offs, says Joro CEO Sanchali Pal.
"We have a sense that 1,000 calories is a lot, 10 is a little," she says. "Hopefully, we eventually have a sense that a cross-country flight is about 1,000 kilograms carbon dioxide equivalent, about as much as a month of regular living. And that flight has about the same impact on our climate as eating 200 beef burgers or driving a car around for a few months.”
In the San Francisco–to–Los Angeles case, considering the full emissions impacts of flying clearly reveals that traveling slower by bus or car is likely the most impactful choice the traveler could make that month, Pal says. “If they look at the incomplete CO2 impacts, the relative impact of that choice versus others becomes a lot less clear,” she says.
Google's emissions estimates for that flight would have been higher before last July, when it dropped the impacts of contrails after criticism from airlines, as the BBC first reported. Google says it made the decision independently to reduce uncertainty. "What we know right now is contrails make a big contribution, but there isn’t a good model for looking at that," Google’s Brandt says, noting more study is needed to model variations by region or time of day. Further changes will come to Google’s flight estimates: The company joined a task force with big airlines and researchers in November to tackle the issue.
Google’s decision to drop the contrails data for now has frustrated some climate experts. "While it is fair and true to say that contrails need to be studied in more detail, the first step in that direction should not be to remove their impact altogether," says Ulrike Burkhardt of the German Aerospace Center’s Institute of Atmospheric Physics.
Oncarbon, which sells a flight emissions calculator to online travel agencies, says it had told Google that its methodology returned results that were too low even before it removed the contrails. “We just have this feeling that people have a right to know, and they have a right to know actual numbers,” says Joanna Kocik, a spokesperson for Oncarbon. “It’s like when a bag of chips says it has 50 percent less fat but there are still 600 calories.”
While some airlines support emissions labeling as a concept, they are not exactly happy with Google even after it revised its estimates. The National Air Carrier Association, which represents low-cost US airlines, says some of its members pushed for the scaling back that Google introduced in July but that the members are keeping a close eye on what comes next.
The trade groups Airlines for Europe, European Regions Airline Association (ERAA), and Airlines for America all say calculations need to take into account additional factors, including individual airlines’ sustainable fuel usage and offset purchases.
ERAA, whose members include Azores Airlines and Loganair, says Google’s current model will inevitably favor low-cost carriers and larger aircraft and will potentially mislead consumers on the least polluting option.
Similar criticism has come from the meat industry since Google in September announced plans to show a chart of emissions from different proteins such as chicken and tofu alongside recipe search results. The company says it has seen user interest in understanding food choices.
Google worked with the UN to draw on data about popular meats and alternative proteins from a well-known global study by European researchers. Joseph Poore, a researcher at the University of Oxford who was involved in that study but is not working with Google, describes the report’s data as the most comprehensive available and says the search feature is incredibly important. “It provides information on one the 21st century’s most decisive problems—climate change—directly to people when they are making choices about what to eat,” he says.
The US National Cattlemen’s Beef Association of livestock ranchers is less supportive. After a query about the group’s view of Google’s project in October, it issued a press release denouncing "Google’s decision to bias consumers against beef through their new sustainability search feature that provides inaccurate climate information on cattle production."
Don Schiefelbein, a Minnesota rancher and president of the association, says the global averages Google is using for emissions of several types of meat fail to take into account that the US industry ranks lower than peers such as Brazil in emissions. Google also fails to promote the environmental benefits that raising cattle has over some other foods, such as preserving green space and using less water, he says.
Not only US cattle farmers have doubts about Google’s approach. A spokesperson for the UK industry group Agriculture and Horticulture Development Board says that listing only emissions impacts is not enough, because the overall sustainability and environmental impact of foods also depends on other factors such as biodiversity preservation and pesticide pollution.
As Google adds climate-related features and they grow more influential, the company will likely encounter outrage from additional businesses with vested interests. One of its Maps options directs drivers on what the company calls more “eco-friendly” routes. It prevented emissions equivalent to taking 100,000 cars off the road in its first few months in the United States and Canada, according to Google.
Complaints about eco-friendly routing have not yet broken out in public. But Jeff Gonder, a US government mobility and energy researcher who advised Google on the feature, speculated that it could be possibly navigating drivers away from certain toll roads that enable higher speeds, burning more fuel, on less direct paths.
The International Bridge, Tunnel and Turnpike Association disputes that theory, pointing to tolled routes that can actually be eco-friendlier because they require less merging and slowing down due to better roadway conditions and more direct paths.
UC Davis animal science professor Frank Mitloehner, who works closely with farmers and ranchers, says consumers appear condemned to be confused by internet services pushing emissions estimates on them as they shop or seek other information online. “It’s bugging me that these things that are complicated and nuanced are being simplified in ways that lead to inaccurate choices,” he says.
