Price drop.

A drop in the EU's carbon price this year could mean the bloc's key cleantech fund will be smaller than budgeted and potentially jeopardize some low-carbon projects in the EU, Reuters reported.

This is big. Carbon prices hovered above 100 euros per ton of CO2 last year, but nearly halved by February. The fall has wiped out 4.1 billion euros in potential revenues for low-carbon investments.