OPINION: More trees won’t cancel out your SUV emissions

As far as climate buzzwords go, “Net Zero” has probably become the most weaponized term. It may also be the most misunderstood.

Lots of people recognize that reaching net zero carbon emissions is key to meeting the temperature goals of the Paris Agreement. But how many of us have an accurate understanding of what that means?

A group of scientists who developed the science behind net zero 15 years ago have authored a new study, published in Nature, warning that our heavy reliance on natural carbon sinks to offset fossil-fuel emissions is a misunderstanding of the original idea. A course correction is more important than ever, particularly as developments at the 29th United Nations climate change conference, also known as COP29, will likely further incentivize the equivalence between fossil-fuel emissions and natural drawdown.

Let me break down the jargon. Net zero refers to the idea that our carbon emissions are balanced to zero, so that we’re no longer increasing the concentration of greenhouse gases in the atmosphere. There are some technical equations in the paper, but a simplified one to illustrate basic net zero would be:

Human emissions + human land-use change = 0

Now, carbon sinks — oceans, forests, peatlands — play a key role in drawing down and storing carbon. And we rely on these natural resources to balance our emissions equation leading to an equation, which looks more like:

Human emissions + human land-use change — passive carbon sinks = 0

This poses some problems.

The second equation may stabilize the level of atmospheric CO2, but it also means that warming would continue. This is because the planet is currently absorbing more energy from the sun than is escaping back into space. Eventually, an equilibrium would be reached as the extra heat is absorbed by the deep oceans, but this would take a long time (think centuries), and in the meantime, we’ll get warmer. The paper notes that if atmospheric concentrations were fixed at today’s levels, the most likely eventual warming level would still exceed 2C above pre-industrial temperatures — and that would risk taking us far above the goal of the Paris Agreement.

Happily, scientists found that if passive carbon sinks were able to bring down atmospheric CO2, the continued surface warming would be canceled out.

And so carbon removal is extremely important for securing a friendly and stable climate for ourselves and our descendants. But there are two roles here — offsetting our own continuing emissions from burning oil, gas and coal, and cleaning up the mess we’ve already made. Our forests and oceans can’t do both jobs. Land is a finite resource in competition with our other needs such as food, shelter and energy, so there’s a limit to the carbon-absorbing capacity of Earth’s natural spaces.

That’s especially true as climate change is destabilizing our carbon sinks. Just look at New York, where the Jennings Creek fire has burned for more than a week. The Canadian wildfires in 2023 released more than 645 million metric tons of carbon into the atmosphere, comparable to the annual emissions of large nations, with only India, China and the US releasing more carbon per year.

When we burn fossil fuels, the resultant pollution is permanent — without intervention, CO2 will stay up there for somewhere between 300 and 1,000 years. We can no longer say that the carbon stored in our trees would last nearly that long.

This doesn’t mean there’s no place for any offsets in the net zero equation, but the standard needs to be higher.

Myles Allen, professor of geosystem science at the University of Oxford and lead author of the report, said that the aim by mid-century should be “Geological Net Zero” — meaning that “any carbon that still comes out of the ground will have to go back down, to permanent storage.” That may encompass technologies such as ocean alkalinity enhancement and direct air capture. Of course, these methods are expensive and challenging — so all the more reason to leave fossil fuels below our feet.

Unfortunately, global climate standards are encouraging nations and corporations to lean on nature to do the hard work of decarbonization.

In its assessment of anthropogenic CO2 removals, the Intergovernmental Panel on Climate Change (IPCC) explicitly excludes natural CO2 uptake that isn’t directly caused by humans. But other reporting systems, including national greenhouse gas inventories, allow passive sinks to be included as a removal if it takes place on “managed land,” which countries can self-determine.

This little loophole means that we could halve greenhouse gas emissions without lifting a finger. Russia, for example, could say that it’s reached net zero emissions simply by counting its vast forests as managed land. In fact, that’s basically its plan. In its 2020 climate action plan, it said it would reduce greenhouse gas emissions by 70% relative to 1990 levels by 2030, while “taking into account the maximum possible absorptive capacity of forests and other ecosystems.” As the fourth biggest polluter, it’s worrying that the country could say “job done” while continuing its dirty ways.

Some nations have already taken this approach: Gabon and Suriname have packaged up their rainforests for sale in the form of carbon credits. It’s not hard to imagine a future where island states try to take credit for the carbon passively absorbed by the oceans of their exclusive economic zones. This approach risks being further legitimized now that key elements of a new carbon market under the Paris Agreement have been approved at COP29 in Baku, Azerbaijan. Unless removals from passive carbon sinks are excluded from the market, countries will continue to pursue a misconstrued version of net zero.

So how do we move forward? There should be greater distinction between “biological” removals via carbon sinks and “geological” emissions from fossil fuels in climate reporting and targets, and a ton of one shouldn’t be fungible with a ton of the other. Not a single country or company has made these distinctions — but there’s a slice of history waiting for the first entity to go beyond the current requirements.

Lara Williams is a Bloomberg Opinion columnist covering climate change. This column does not necessarily reflect the opinion of the editorial board or Bloomberg LP and its owners.

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