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."

Climate pledge

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.