Not all carbon credit projects are cooling the planet

For years, forest-based carbon credits have been treated as a go-to solution in the fight against climate change. Trees are planted, they absorb carbon dioxide from the air, and the captured carbon is sold as credits. It sounds very straightforward.

However, a new study shows that some of these carbon credit projects might be doing the opposite of what they promise – by actually making the planet warmer.

When sunlight bounces back

Trees are great at soaking up carbon dioxide. But there’s something else going on when you plant a forest: it changes the way sunlight interacts with the ground.

This is based on albedo – a measure of how much sunlight is reflected off a surface. Snow and light-colored ground reflect a lot of sunlight. Dark forests? Not so much. They actually absorb more heat.

If trees are planted in places that used to reflect a lot of sunlight – like grassy plains or snowy regions – more heat may be trapped in the atmosphere, even if some carbon dioxide is removed.

The carbon-albedo tradeoff

A research team looked at 172 carbon credit forestation projects across five continents. These projects are part of the Voluntary Carbon Market – a system where companies and governments buy carbon credits to offset their emissions.

One carbon credit is equal to one metric ton of carbon dioxide removed from the atmosphere.

These projects are expected to cancel out about 800 million tons of CO₂ over the next 100 years. But that’s only if you count carbon and ignore albedo.

When the researchers included albedo in the math, the numbers changed. Some of those credits weren’t as effective as advertised. In fact, for 10% of the projects, the overall effect was warming, not cooling.

For 12% of the projects, the entire climate benefit was wiped out once albedo was factored in.

This doesn’t mean the whole carbon credit system is broken. But it does mean we need to get smarter about how we evaluate these projects.

Carbon credits and climate benefits

The study was led by researchers in Oregon State University’s College of Forestry. The team included scientists from Clark University and The Nature Conservancy.

The experts used newly available public data to analyze how albedo plays into carbon credit projects – specifically afforestation, revegetation, and reforestation (or ARR).

Afforestation means planting trees where there weren’t any before. Reforestation brings trees back to areas that used to have them. Revegetation restores other types of plant life.

“Carbon credits are created via established protocols that aim to ensure each credit corresponds to an actual climate benefit,” said Lynn Riley, a scientist with the American Forest Foundation.

“But so far, those protocols have only accounted for greenhouse gases while largely omitting the non-greenhouse gas factors that also can have a big impact on climate.”

Measuring the albedo impacts

The team found that for all 172 projects, the median albedo deduction – the percent of climate benefit lost due to heat absorption – was 18%.

That means, on average, nearly a fifth of the cooling power of these projects was being canceled out by extra heat from darker surfaces.

Here’s the upside: most of the projects studied had fairly small albedo impacts. And some actually had a positive albedo effect – they increased reflectivity and added to their climate benefit.

“I was encouraged to find that a majority of forest restoration projects have small albedo deductions, indicating that albedo changes are likely negating only a small fraction of the carbon-related climate-cooling benefits,” said Riley.

“And another portion of projects, most of them in tropical and subtropical regions, have albedo benefits that are unaccounted for, indicating they may be providing even greater climate cooling than they’re credited for.”

Carbon credit projects that work

The results suggest that some projects are doing more to fight climate change than we thought. The study also shows that there’s room to improve how we measure their impact. The researchers say we now have the tools to do better.

“What’s really exciting is that we have independent, accessible data with global coverage to start preventing this today,” Riley said.

“It’s something that actors across the market – project developers, buyers, ratings agencies, policymakers, etc. – could begin to relatively simply and transparently incorporate into their workflows. That will help climate financing flow to the most impactful projects.”

Creating reliable carbon credit markets

More accurate accounting could mean that the best, most effective projects get more funding. That’s especially important as countries and companies put more money into carbon offsets.

“Carbon crediting projects have taken lots of criticism in recent years, but one thing they have done well is evolved with the best available science,” said Jacob Bukoski, assistant professor at Oregon State.

“Albedo and other non-carbon climate benefits like evapotranspiration and snow cover duration could be credited in the carbon market once additional science and accounting have been developed to do so credibly,” noted Riley.

A powerful tool for climate action

This kind of work matters because forestation projects – when done right – are one of the few tools we have that can remove carbon from the atmosphere at scale.

“When they are designed with integrity and informed by the best available science, carbon market projects are a powerful and necessary tool for mitigating climate change,” said Susan Cook-Patton, a forest restoration scientist at The Nature Conservancy.

“This study adds to the growing body of science that is helping ensure the voluntary carbon market meets rigorous standards and nature-based solutions to climate change are implemented with precision.”

Carbon credits aren’t magic. They’re only as good as the science behind them. And now, the science just got better.

The full study was published in the journal Nature.

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