Isn't selling 'carbon credits' like the Catholic Church selling indulgences?

i'm not catholic so i'm not going to address the indulgences part, but there is nothing wrong in itself with the carbon credits idea. wind power, planting a tree, ect. are good for the environment. however global warming/climate change is a bunch of bad science. the climate goes in cycles of roughly 20 years. anyone here old enough to remember hearing that we were heading into an ice age?