Sens. Amy Klobuchar and Al Franken joined 12 other lawmakers in a letter to Senate leaders Thursday urging them to reconsider how cap-and-trade legislation is formulated.

"Cap-and-trade" refers to a proposed system for regulating carbon emissions which would convert the right to emit carbon into a limited commodity to be distributed by the government and traded among companies.

The House of Representatives passed such legislation this summer and a similar bill recently emerged from a Senate committee.

The senators argued that a plan already approved in the House to give companies a certain amount of carbon credits based equally on their sales and emissions wouldn't provide enough for utilities which are heavily dependent on coal. Those companies would then have to purchase additional credits, a cost the senators say will be passed on to the consumer.

Minnesota is one of several states that are heavily reliant on coal for electricity.

Instead, they are asking for credits in the electricity sector to be calculated fully based on emissions, therefore initially allocating more to those coal-dependent companies

"We believe it is essential that we strive to formulate legislation that equitably distributes transition assistance across individuals, as well as states and economic sectors," the senators wrote along with their colleages.

The letter was addressed to Senate Majority Leader Harry Reid, Finance Committee Chairman Max Baucus, Environment and Public Works Committee Chairwoman Barbara Boxer and Foreign Relations Committee Chairman John Kerry.

Read the letter here.