Countries are taking shortcuts to net-zero emissions by including forests and other “passive” carbon sinks in their climate plans, a tactic that thwarts global efforts to halt climate change. leading researchers have warned.

Relying on natural carbon sinks to absorb continued carbon emissions from human activities will keep the world warmer. This comes from the researchers who first developed the science behind net zero emissions and today launched a highly unusual intervention accusing nations and companies of abusing the concept.

“This document calls on people to be clear about what net zero really means.” Miles Allen The Oxford University professor said this at a press conference on November 14th.

Natural sinks such as forests and peat bogs play an important role in the Earth’s natural carbon cycle by absorbing some of the carbon from the atmosphere. However, we cannot rely on existing sinks to offset ongoing greenhouse gas emissions.

If used in this way, global atmospheric carbon dioxide concentrations would remain stable even when we reach “net zero,” and warming would continue for centuries due to the way the oceans absorb heat. Allen warned. “Even if we think we’re on the path to 1.5C, we could end up with temperatures rising well above 2C,” he says. “This ambiguity could effectively destroy the goals of the Paris Agreement.”

To halt global temperature rise, we need to reduce emissions to net zero, without relying on passive absorption by land and oceans. This allows existing natural sinks to continue absorbing excess CO2, reducing the concentration of the gas in the atmosphere and offsetting ongoing warming from the deep ocean.

However, many countries already count passive land sinks such as forests as greenhouse gas removals in their national carbon accounts. In some countries, such as Bhutan, Gabon, and Suriname, Already declared net zeroThanks to the existing vast forests.

Some companies are setting long-term net-zero targets based on this approach. For example Russia Pledging to achieve net-zero emissions by 2060but this plan relies heavily on using existing forests to absorb ongoing carbon emissions.

“Maybe some countries will use this in a deliberately naughty way.” glenn peters He is from the CICERO International Climate Research Center in Oslo, Norway, and spoke at a press conference. “This problem will be even more problematic in countries where forest area is a large proportion of total land area.”

The researchers fear this problem will become more serious as carbon markets develop and pressure on countries to decarbonize increases. “As the value of carbon increases, there will be more pressure to define anything that can be removed as a negative emission, potentially to be able to sell it in the carbon offset market,” Allen said.

Countries and companies with net-zero targets will need to modify their approach to exclude passive carbon sequestration from their accounts, the researchers say.

Natural sinks count as carbon removal when they are added to existing ones, for example when new forests are planted or peat bogs are rewetted. However, this type of natural carbon sink is vulnerable to climate impacts such as wildfires, drought, and the spread of invasive species, and is unreliable for long-term sequestration.

This has not stopped countries from relying heavily on these natural sinks in their net-zero strategies. one 2022 survey It turns out that a number of countries, including the United States, France, Cambodia and Costa Rica, plan to rely on forest carbon and other naturally occurring removals to offset ongoing emissions. “Many national strategies ‘bet’ on increasing carbon sinks in forests and soils as a means of achieving long-term goals,” the study authors wrote.

Allen stressed that natural carbon sinks must be conserved but not relied on to balance ongoing emissions. Instead, he urges countries to aim for “geological net zero,” where all ongoing carbon emissions are balanced by long-term carbon sequestration in underground storage.

“Countries need to recognize the need for geological net zero,” he said. “That means if we are producing carbon dioxide from burning fossil fuels by mid-century, we need to have a plan to put that carbon dioxide back into the ground.”

“Geological net zero seems like a sensible global goal for countries to aspire to,” he says. harry smith At the University of East Anglia, UK. “This will help clarify many of the ambiguities that plague the current way countries consider land travel.”

But he warns that it could have a knock-on effect on climate ambitions. “What does the new politics of geological net zero look like? If geological net zero drives the goals of governments’ climate strategies, what does this mean for governments’ climate change ambitions?” Will it have an impact?”