ABC News On Campus reporter Andrew Egan blogs: In the more than 40 years since Rachel Carson’s book "Silent Spring" established environmental concern in the national consciousness, the movement has often been considered a political afterthought. Tim Greeff, a lobbyist for the League of Conservation Voters (LCV), says it’s this generation that is making the environment a priority. "Look at the Senate, and this goes across party lines, 24 members are over the age of 70," Greeff says. "They didn’t grow up in a time of environmental consciousness." The LCV is a non-partisan Washington, D.C.-based environmental advocacy group that releases the standard rating for members of Congress environmental positions. The organization counts both Republicans and Democrats among its highest-rated members, though the GOP represents only 20 percent of LCV endorsements. The two presidential campaigns have different views on environmental issues. "Actually, [McCain] hasn’t taken a vote on a key piece of environmental legislation since April 2006," Greeff said. For its part, the McCain campaign says it recognizes global warming as a significant threat. "[McCain] believes in global warming and sees it as our foremost environmental concern," said Brian Rodgers, a McCain spokesman. Here’s a breakdown of the candidates’ stance on environmental issues: Cap-and-Trade System for Emission Control Each candidate supports a cap-and-trade system which would attempt to control carbon emissions by providing economic incentives to do so. McCain: Reduce carbon emissions 60 percent of 1990 levels by the year 2050. Obama: Reduce carbon emissions 80 percent of 1990 levels by the year 2050. Offshore Drilling McCain: The senator plans to expand offshore drilling to loosen America’s dependence on foreign oil: "The current federal moratorium on drilling in the Outer Continental Shelf stands in the way of energy exploration and production," McCain’s Web site says. Obama: While generally opposed to expanding offshore drilling, Obama has shown flexibility in order to pass legislation, saying, "If we can come up with a genuine, bipartisan compromise in which I have to accept some things I don’t like … than that’s something I’m open to." Alternative and Renewable Energies McCain: While touting the need for $2 billion in clean coal technology and 45 new nuclear power plants by 2050, the senator also supports renewable energy, though he has yet to set specific targets. Obama: Has a general openness to a possible energy solution but places emphasis on renewable sources seeking to "ensure 10 percent of our electricity comes from renewable sources by 2012, and 25 percent by 2025," according to Obama’s Web site.