Carbon offsets have become big business as more companies make promises to protect the climate but can’t meet the goals on their own.

When a company buys carbon offsets, it pays a project elsewhere to reduce greenhouse gas emissions on its behalf – by planting trees, for example, or generating renewable energy. The idea is that reducing greenhouse gas emissions anywhere pays off for the global climate.

But not all offsets have the same value. There is growing skepticism about many of the offsets sold on voluntary carbon markets. In contrast to compliance markets, where companies buy and sell a limited number of allowances that are issued by regulators, these voluntary carbon markets have few rules that can be enforced consistently. Investigations have found that many voluntary offset projects, forest management projects in particular, have done little to benefit the climate despite their claims.

I specialize in sustainable finance and corporate governance. My colleagues and I recently conducted the first systematic, evidence-based look at the global landscape of voluntary carbon offsets used by hundreds of large, publicly listed firms around the world.

The results raise questions about how some companies use these offsets and cast doubt on how effective voluntary carbon markets – at least in their current state – are in assisting a global transition to net-zero-emissions.

Our analysis shows that the global carbon-offset market has grown to comprise a rich variety of offset projects. Some generate renewable energy, contribute to energy-efficient housing........

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