Based on the aggregated intelligence of 180,000-plus investors participating in Motley Fool CAPS, the Fool's free investing community, the iPath Global Carbon ETN (NYSEMKT: GRN) has received the dreaded one-star ranking.

With that in mind, let's take a closer look at GRN and see what CAPS investors are saying about the ETF right now.

GRN facts

Inception

June 2008

Total Net Assets

$920 thousand

Investment Approach

Seeks to replicate the Barclays Capital Global Carbon Index Total Return. The index is designed to measure the performance of the most liquid carbon-related credit plans and is designed to be an industry benchmark for carbon investors.

Expense Ratio

0.75%

1-Year / 3-Year / 5-Year Return

(56.6%) / (42%) / (36.2%)

Sources: S&P Capital IQ and Motley Fool CAPS.

On CAPS, 54% of the 28 members who have rated GRN believe the ETF will underperform the S&P 500 going forward.

Just yesterday, one of those Fools, All-Star TerryHogan, succinctly summed up the GRN bear case for our community:

People are too busy looking for jobs to care about carbon emissions. Besides, there is already a huge transition to cleaner forms of energy (Natgas is so cheap in North America). Until China and India are growing faster than [8% per year] I'm not too bullish on the future of carbon credits.