Access Carbon-Trading Market Via This ETN

Now to bring in a little politics, people who do believe global warming is a problem might be inclined to view GRN as a one-way trade. The folks who are not concerned about global warming would view this is a poor investment.

Even if the skeptics are right about the importance, it would seem that news flow and awareness will only increase, which provides a tailwind -- but not a one-way trade -- for all carbon indices.

One last thing: GRN is a debt obligation of Barclays PLC (BCS Quote), the same Barclays whose stock price is down 40% year to date (far worse than that of the Financial Sector SPDR (XLF Quote)).

The company recently raised $4.5 billion in capital, and some say more capital may be needed.

I think a failure of Barclays is extremely unlikely, but anyone considering one of the iPath ETNs needs to follow the story.