Carbon offsets used by corporations around the world to lower their reportable greenhouse gas emissions are “ineffectual” and “hindering the energy transition”, according to more than 60 leading climate change scientists.
A pledge signed by scientists from nine countries, including the UK, US and Australia, said the “only path that can prevent further escalation of climate impacts” was “real zero” and not “net zero”.
The “real zero pledge” was organised by the Lethal Humidity Global Council, a group of scientists, health experts and policymakers.
Among the signatories are Prof Michael Mann, of the University of Pennsylvania; Prof Johan Rockström, director of the Potsdam Institute for Climate Impact Research; and Bill Hare, founder of Climate Analytics and a member of a UN expert group that has warned about the overuse of carbon offsets.
“We should be focused on real reductions in emissions, rather than engaging in a counting game,” Hare said.
The pledge reflects growing concerns that large amounts of carbon offsets generated from forest-related projects or, in Australia, from avoided land clearing, and then traded, may not have actually reduced emissions.
The Lethal Humidity Global Council is a group focused on the threat of rising temperatures that, when combined with high humidity, can threaten human health.
Prof Katrin Meissner, director of the Climate Change Research Centre at the University of New South Wales and a signatory, said many offset programs focused on growing trees or allowing areas to regrow.
But she said these could not lock carbon away forever because when the trees die, such as in droughts or wildfires, they rereleased the carbon back into the atmosphere.
“A reliance on carbon offsets without the needed emission reductions is dangerous and detrimental,” she said.
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“To keep global warming within the guardrails of the Paris agreement, the timeframe is now so tight that there is no space for companies to use offsetting to continue high-carbon activities. We need to turn the fossil fuel taps off, all of them.”
Prof Sarah Perkins-Kirkpatrick, another signatory and climate scientist at Australian National University, said: “In many ways ‘net zero’ is a Band-Aid solution because it doesn’t fix the problem at the source.”
Russell Reichelt, a veteran public servant and Australian ambassador on sustainable oceans, said many offsets relied on the ability of the land and ocean to act as a sink for greenhouse gas emissions.
But he was concerned that these natural sinks, such as forests and oceans, were already struggling to absorb the extra CO2 humans were emitting.
Reichelt was a member of Australia’s Climate Change Authority which last year said the country’s official carbon credit system was helping to “smooth the transition to net zero”.
The council organising the pledge is convened by the Minderoo Foundation, co-founded by iron ore mining billionaire Andrew Forrest, who has described net zero as a “fantasy” and urged companies to focus on ending their use of fossil fuels instead.