As alarm at the United Nations over climate change has grown dire in recent years, a slew of corporations have announced net-zero carbon emissions goals.
More than 300 major companies, including Amazon, Procter & Gamble, HP and Salesforce, have now signed onto a pledge to achieve net-zero emissions by 2040. Net-zero pledges from countries cover about 70% of global gross domestic product and carbon emissions, the International Energy Agency said in a report last May.
But net zero -- which calls for a neutral carbon impact through the removal of the same amount of emissions from the atmosphere that an entity releases -- has drawn backlash from activists and some experts. The approach allows companies to continue releasing significant amounts of carbon while pursuing emissions offsets, which are difficult to verify and sometimes rely on technology that has yet to be developed, environmental advocates told ABC News.
Many advocates have called for companies to instead pursue a goal of "real-zero" emissions, which calls for the outright elimination of carbon emissions. The more ambitious goal would ensure that companies dramatically reduce carbon emissions, and would remove the challenge of developing and vetting carbon offsets, advocates told ABC News.
But the paradigm shift toward real-zero emissions goals remains in its infancy and could bring some economic disruption, dramatically altering or eliminating industries that rely on fossil fuels, such as oil and gas, the advocates said.
Katie Tubb, research fellow on energy and environment issues at the conservative think tank Heritage Foundation, took such concerns further, saying a transition toward real zero would be infeasible for many companies, deliver only a fraction of the carbon emission cuts needed worldwide and potentially increase costs for companies and consumers.
Advocates, however, said the urgent need for carbon emissions reduction requires an ambitious approach like real zero.
"Companies use the mantra net zero as a fig leaf for continuing whatever they're doing," David Klein, a mathematics professor at California State University Northridge, where he participates in the Climate Science Program, told ABC News.
"Think of it as a pot of water being heated by a flame underneath it," he added. "As long as that flame is on, as long as energy goes into the system, the temperature will continue to increase. Instead of net zero, we need to decrease the concentration of greenhouse gasses in the atmosphere by radically decreasing emissions."
A U.N. climate report released in April sounded an urgent alarm that the world is on pace to far exceed an increase of 1.5 degrees celsius above pre-industrial temperatures -- a level beyond which many scientists say climate change will wreak damaging effects. At the Paris Climate Accords in 2015, 196 parties committed to set a goal of well below 2 degrees celsius of warming, preferably below 1.5 degrees celsius of warming.
"It's now or never if we want to limit warming to 1.5 degrees celsius," Jim Skea, a professor of sustainable energy at Imperial College London, said in a statement upon the release of the April U.N. climate report. "Without immediate and deep emissions reductions across all sectors, it will be impossible."
The U.N., which said it supports an eventual net-zero economy worldwide, acknowledged the importance of verifying commitments to net zero. The U.N. says on its website that net-zero commitments "must be backed by credible action." In March, U.N. Secretary-General António Guterres established a group of experts who will recommend standards for net-zero emissions pledges.
But assessment of an entity's fulfillment of a net-zero goal poses a significant, potentially insurmountable, challenge that detracts from the global effort to reduce carbon emissions, said Tyson Slocum, director of the energy program at the consumer advocacy group Public Citizen.
"The ability to effectively oversee and verify these programs is very difficult," he said, noting the challenge of not only estimating a company's emissions but also the carbon savings delivered by its offsets. "Even if we had better protocols there are concerns about how that's going to work effectively."
"A lot of the push around net zero and its reliance on offsets is actually a distraction from meaningful action to address the climate crisis," he added.
The rapid development of renewable energy sources has equipped industry with the necessary resources to embark on the shift to real zero, environmental advocates said. Last year, renewable energy sources accounted for about 12.2% of total U.S. energy consumption and about 20.1% of electricity generation, the IEA said. Worldwide, the share of renewable energy in electricity generation stood at 29% in 2020, the group said.
Still, few companies have taken up the goal of real zero. One such company, NextEra Energy, is a holding company that oversees Florida Power & Light, a utility company that serves more than 12 million people in the state and aims to achieve real-zero emissions by 2045.
The company believes it can preserve the reliability and competitive price of its electricity while eliminating emissions, Chris McGrath, the communication leader at Florida Power & Light, told ABC News.
"Real zero for us is not a goal that relies on offsets," McGrath said. "We're pursuing real zero because we think it's achievable. We think the technology exists now that we'll be able to eliminate emissions and keep the lights on 24/7."
The company plans to achieve real zero by expanding the share of energy it derives from solar, improving battery storage that holds solar energy through dark periods overnight or when it's cloudy, continuing its nuclear energy operations and developing green hydrogen technology, McGrath said.
Green hydrogen technology would use renewable energy to power a process that extracts hydrogen from water, allowing the hydrogen to be used for tasks like powering vehicles or generating electricity. But the technology has not yet been developed, leaving the real-zero goal of Florida Power & Light open to criticism that it relies on technology that doesn't currently exist, just as some net-zero goals do.
In response, McGrath said the technology doesn't represent a major leap in development.
"Burning hydrogen is not a new technology," McGrath said. "What's unique for us is using solar power to power the process."
"We don't pretend there aren't going to be challenges associated with achieving this goal but we've been on this journey for more than two decades," he added.
Environmental advocates said rapid progress in renewable energy technology has brought real-zero carbon emissions goals within reach, but they acknowledged that the shift would disrupt the economy and dramatically impact industries that rely on fossil fuels.
"There are some industries, like an airline or a big oil company, where that's going to be a bit of a challenge," said Slocum, the director of the energy program at Public Citizen. "They can't really effectively get to real zero."
The availability and affordability of renewable energy will ease the transition for many companies, he added.
"There are all sorts of readily available technologies employable and affordable that companies and other entities can incorporate into their systems," he said.
Tubb, the research fellow on energy and environment issues at the conservative think tank Heritage Foundation, rejected such a rosy outlook. Real-zero emissions cuts from the narrow set of U.S. companies that could access large-scale renewables in the short term would only make up a fraction of the emission cuts needed worldwide, she said. Plus, the significant shift in operations will impose costs on companies and consumers, she added.
"This is a lot of expense for a company to take on with dubious environmental benefits on the global warming side of things," she said.
Rolf Skar, the campaign director for environmental advocacy group Greenpeace USA, said the call for wide scale commitment to real zero is realistic rather than radical, considering the current pace of carbon emissions and the threat posed by climate change.
"If it's radical, it's radical because of the necessity of the crisis we're in now," he said.