The hope is that allowing negative emissions to balance continued CO2 emissions as part of net-zero policies will provide a safety net for industries where it is technically impossible to eliminate all emissions—in aviation and agriculture, for instance. The negative emissions might be achieved by increasing CO2 take-up by forests and other ecosystems, or by using industrial chemistry to capture CO2 from the air. But some fear the safety net will become a cover for business-as-usual in highly polluting industries.

The debate is as much about the politics of driving down emissions as about climate science or the potential of technology.

Watson was chair of the IPCC from 1997 until 2002, when the U.S. administration of President George W. Bush refused to nominate the former NASA climate scientist for a second term. Since then he has worked as an academic, currently at the University of East Anglia. He and his co-authors wrote last month that while net zero might be “a great idea, in principle,” in practice it “helps perpetuate a belief in technological salvation and diminishes the sense of urgency surrounding the need to curb emissions now.” Scientists who support the current push for net-zero, they contend, have “licensed a recklessly cavalier ‘burn now, pay later’ approach, which has seen carbon emissions continue to soar.”

Protecting business as usual

Watson and his colleagues admit to their own roles. “We admit that it deceived us,” he and fellow climate scientists James Dyke of Exeter University and Wolfgang Knorr of Lund University in Sweden wrote. But “the time has come to voice our fears and be honest with wider society… Current net zero policies will not keep warming to within 1.5 degrees, because they were never intended to. They were and still are driven by a need to protect business as usual.”

Watson’s stand—especially coming from a former IPCC boss—has angered some fellow researchers. In a riposte published this month, Richard Black at Imperial College London said it makes little sense to attack net zero when it is “the defining lens through which many governments, businesses, NGOs and other types of entity view decarbonization.” Black told Yale Environment 360, “high-carbon advocates have always found excuses to delay, and would do so whatever the policy framing.” But “it has nothing to do with net zero per se.”

In any case, Black is upbeat. In March, he was lead author of an analysis of net-zero commitments that argued that “the global momentum on net zero represents an exciting window.” Besides 124 national governments committing to adopting various versions of net zero as targets, he found net-zero pledges from more than 1,500 major companies, representing $14 trillion in revenues.

Black agrees that not all these governments and businesses intend to honor their pledges. And auditing whether they do so is particularly difficult where those pledges involve offsetting their continued emissions by buying paper certificates from other organizations that claim to have prevented emissions elsewhere or absorbed CO2 in forests.

“There are big flaws in how net zero is being implemented in some cases,” Black said. “But pledging a target means that the entity can be held to account by voters, shareholders, or customers.”

This is happening, Black says. He cites the example of the German government. Last month the country’s highest court ordered it to up its short-term emissions reductions to ensure that its mid-century net-zero target did not leave a disproportionate share of the responsibility to future generations.

Holding industry to account

Industries, too, will be judged. The fossil-fuel industry’s public commitments to net zero by 2050 will from now on be compared with a detailed road map for achieving net zero across the energy industry published this month by the International Energy Agency (IEA), an intergovernmental body long considered by environmentalists as an apologist for fossil fuel companies.

No longer. The IEA now says that meeting net zero requires an immediate worldwide end to approvals of new oil and gas fields—meaning that all drilling for more oil or gas reserves should cease. This puts it at odds with oil giants that are promoting corporate net-zero strategies while continuing to search for more oil.

These include Shell. Its shareholders this month endorsed a strategy for making its business net zero by 2050. But a minority protested that the strategy contravenes the IEA’s call to end all fossil-fuel expansion now. Instead, the Shell plan anticipates a 20% increase in gas production by 2030.

Shell’s version of achieving net zero relies heavily on investment in forest projects to offset its emissions. Several have already proved controversial. Following an analysis of the company’s net-zero strategy that they coauthored, Johan Rockstrom of the Stockholm Resilience Center and Gail Whiteman of the University of Execter said the negative emissions that Shell will need to offset its continued fossil-fuel activity “requires a forest the size of Brazil.”

Rockstrom and Whiteman call for the company to be drummed out of net-zero initiatives, such as the UN’s Race to Zero campaign, and questions its role advising the British government in the run-up to the Glasgow climate conference.

IEA director Fatih Birol also says net zero requires a global program for early shutdown of coal-fired power stations, especially in Asia. Yet signatories to net-zero policies, including the government of China, continue to fund new coal-plants, as do major finance houses such as Barclays and BNP Paribas, despite both joining a UN Net-Zero Banking Alliance.

Just get someone else to pay for it

Some environmental NGOs, such as The Nature Conservancy, nonetheless back net zero and have created their own offsetting projects to help companies take advantage of emission offsets. But others decry it. Friends of the Earth calls it “chasing climate unicorns,” allowing polluters to “hide behind the ‘net’ in net zero, claiming that they just need to pay someone else to remove carbon.”

Dyke told e360: “Net zero policies are best understood as the latest manifestation of a dysfunctional climate policy system”—the latest “framing” by apologists for the status quo.

He believes the slippery slope began in the 1990s when there was a push to persuade a reluctant U.S. to address climate change by allowing it to count the carbon absorbed by its forests as a contribution. The idea, says Dyke, was that “if it managed its forests well,” then the carbon stored “should be subtracted from its obligations to limit the burning of coal, oil, and gas.“

Technological fixes followed. At the climate conference in Copenhagen in 2009, companies promised to develop carbon capture and storage (CCS), the capture of CO2 as it went up power-station stacks for burial underground. But a decade on, he says, there are no such facilities in practical large-scale operation.

By Paris in 2015, the “new savior technology” was Bioenergy with Carbon Capture and Storage (BECCS). This combined CCS with burning wood or other bioenergy crops in power stations. If the wood or other fuel was then regrown, it would absorb more carbon from the air. In this way, the world could combine generating energy and negative emissions.

But since Paris, it has emerged that full deployment of BECCS would require frequently harvested tree plantations or bioenergy crops covering anywhere from 25 to 80 percent of all land currently under cultivation. That would “devastate biodiversity,” according to Watson, who since his stint at the IPCC has also chaired the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services.

“The end result of all these diversions,” Dyke said, “has been the same—no effective mitigation.” Emissions today are 60% above the level of 1992, the year the world first agreed at the Rio Earth Summit to prevent “dangerous” climate change. ”Net zero is just the latest example of wishful thinking that effectively stops us critically reflecting on why we have failed,” he said.

Will ‘nature-based solutions’ do the trick?

In the search for means of achieving negative emissions to meet net-zero targets, there has been an increasing focus on what are called “nature-based solutions.” These involve using forest planting or restoration of carbon-holding wetlands, such as peat bogs or mangrove swamps, to draw CO2 from the air.

The term was coined in 2017 by Bronson Griscom, then at The Nature Conservancy. In a new analysis by him and others in the journal Nature this month, Griscom says they “can have a powerful role in reducing temperatures,” including in the long term, if they are properly designed and have good accounting standards.

But this too has drawn the ire of Watson and his co-authors. Knorr told e360 that while it was true that restored ecosystems can hold more carbon, calculating any additional benefit from short-term interventions is all but impossible. It is also wide open to misrepresentation, he said, as companies and countries adopt natural carbon sinks as part of their plans for net zero.

“About a third of current CO2 emissions are taken up by forests and other ecosystems,” Knorr said. “Double counting is essentially unavoidable. We need the natural sink plus mitigation, not the sink as mitigation.”

Potentially even worse, he warns, climate change itself “could weaken forests and make them prone to fires or insect attacks,” at which point they start releasing their carbon. For such reasons “nature-based solutions don’t offer a guarantee that carbon will remain stored away. It’s a Pandora’s box,” Knorr said.

Climate modeler Myles Allen at Oxford University, a co-author of this month’s Nature paper on nature-based solutions, agrees. Climate-based solutions are “temporary and at risk of reversal as the world warms,” he told e360. Most climate models show the biosphere switching from a sink to a source of carbon over the course of this century. “So storing fossil carbon there is risky,” Allen said, “unless you have a plan to re-store it somewhere permanently if it starts to leak out again—which no offsetting schemes even think about.”

Such concerns have not stopped some countries from including their natural sinks in calculating their contributions to climate change. Bhutan and Suriname both claim to be carbon negative because their trees currently absorb more than their industries emit. But this makes no scientific sense, says critics, because they are claiming as part of their CO2 reduction strategies natural processes that are already included in models of future climate. The danger is that other countries may try to join them.

When China recently committed to achieving net zero by 2060, it said that it would achieve this in part through nature-based solutions. The government’s special envoy of climate, Xie Zhenhua, said in 2019 that nature-based solutions could cut China’s net emissions by a third. Last year, in a Nature paper, Yi Liu of the Chinese Academy of Sciences and colleagues calculated that between 2010 and 2016 China’s forests soaked up the equivalent of 45% of its human-made CO2 emissions.

Similarly, the U.S. Forest Service says 11% of national CO2 emissions are “offset” by American forests. If the world’s two biggest emitters start claiming that the carbon being absorbed in these existing forests could be offset against their emissions to achieve net zero, then the scientific basis for net-zero policies to end climate change would swiftly unravel.

Fred Pearce is a freelance author and journalist based in the U.K.