Patrick McCully has a great feature in The Guardian about some of the problems with offsets. (No single article can tackle all of them.)

The points are pretty standard:

Help Grist raise $25,000 by September 30 to further advance our climate reporting
  1. At least two thirds of the offset are fraudulent.
  2. Fraudulent offsets used as permissions to burn coal and increase climate chaos.
  3. Throw in massive supporting evidence in an entertaining package.

Ho freaking hum, right?

Meanwhile, the world keeps burning. Every ton of offset-enabled coal power makes our climate a little sicker.