Patrick Greenfield

In January 2023, the Guardian led a joint investigation into rainforest carbon offsets approved by Verra, the world's leading certifier. It found that the carbon credits used by Disney, Shell, Gucci and other big corporations for their climate and biodiversity commitments were largely worthless, also uncovering allegations of human rights abuse at one scheme in Peru used by Disney, Apple and other leading companies.

Our investigation, which built on three years of research, was read by more than one million people and stretched from Germany to the Peruvian Amazon. It has had a major impact.

After we published, Verra's CEO resigned; Gucci, Leon, Nestle and many other companies are moving away from claims relying on the offsets we investigated; and Delta airlines is being sued in California for its carbon neutrality with a lawsuit that refers to our analysis.

The work of the investigative team - the Guardian partnered with Die Zeit and SourceMaterial - has been discussed in parliaments around the world, and regulatory clampdowns on greenwashing and the use of offsets by the UK's Advertising Standards Authority and EU have followed. The US derivatives regulator has announced a crackdown on fraudulent carbon offsets in the $2bn market.

The work, which led to a fall in demand for the offsets we looked at, is cited in academic studies and investment banking analyst notes. Greta Thunburg and the UN secretary general's office were among the thousands of people that shared it.

While our investigation had many human elements and involved dozens of interviews from the Peruvian Amazon to Germany, it also relied on months of data analysis. To come up with the simple 94% figure about the carbon credits, we had to read through dozens of academic papers, more than 50 project documents - each around 300 pages long - and spend days learning how to apply counterfactual methods and how to make the right comparisons for the avoided deforestation calculations in our analysis.

The research relied on the expertise of professors in ecology, econometrics and carbon science, and we made sure our analysis was checked for mistakes by independent experts before we published. One Cambridge professor who checked our analysis said it was worthy of a PhD, and we have presented our work at Oxford University and Imperial College and have been invited to Stanford next year by a Nobel laureate to give a talk on the investigation.

Our team felt that offsets were at the heart of greenwashing around the world, being used by the oil and gas industry, among others, to count as their route towards net zero and thus posing a real and credible threat to the Paris agreement. We believed that exposing the flaws in this system was strongly in the public interest.