Gresham’s Law says that bad money drives out good. …Something like Gresham’s Law is at work in the carbon offset market, which was set up to fight climate change. Bad carbon credits are driving out good carbon credits. And that’s a big problem for the effort to curb the greenhouse gas emissions. …A report for clients of the British bank Barclays focused on the voluntary carbon market. According to the report, the price of carbon credits has fallen to around $2 per metric ton of carbon dioxide removed from the atmosphere, down from around $9 early last year. That’s not because the cost of reducing emissions is really just $2 a ton. It’s because buyers don’t trust the quality of the credits. They worry that the sellers of credits aren’t doing what they promise. …The Barclays report said that the voluntary carbon market is “undermining the Paris Agreement.” [to access the full story, a NY Times subscription is required]