Environment and energy issues have gained prominence in the 2008 U.S. presidential contest, with Pennsylvania's Democratic primary voters going to the polls on Tuesday, Earth Day, as crude oil prices neared a record $120 a barrel.
Here is what the candidates are saying about energy and the environment:
* Climate Change
New York Sen. Hillary Clinton, Democrat—Cut U.S. greenhouse gas emissions to 80 percent below 1990 levels by 2050 through cap-and-trade system; require all publicly traded U.S. companies to file report on climate change risks with the Securities and Exchange Commission.
Illinois Sen. Barack Obama, Democrat—Cut carbon dioxide (CO2) emissions to 80 percent below 1990 levels by 2050; reduce emissions to 1990 levels by 2020; require fuel suppliers to cut carbon content by 10 percent by 2020.
Arizona Sen. John McCain, Republican—Favors cap-and-trade CO2 approach; sponsored legislation in 2007 to cut emissions by 30 percent by 2050.
* Oil Use
Clinton—Cut foreign oil imports by two-thirds from 2030 projected levels, more than 10 million barrels per day.
Obama—Reduce overall oil consumption by at least 35 percent, or 10 million barrels per day, by 2030 to offset imports from OPEC nations.
McCain—No specified targets. Has said he will unveil "a national energy strategy that will amount to a declaration of independence from the fear bred by our reliance on oil sheiks."
* Vehicle Fuel Economy
Clinton—Boost corporate average fuel economy standards, or CAFE, to 55 miles per gallon by 2030, offer $20 billion in "green vehicle bonds" to help U.S. automakers meet standards, invest in plug-in hybrid technology.
Obama—Double fuel economy standards in 18 years, give automakers tax credits to retool plants and invest in advanced lightweight materials and new engines.
McCain—Has not specified CAFE targets. Voted against energy amendments in 2003 that would have boosted CAFE to 40 mpg by 2015.
Clinton—Make 60 billion gallons of biofuels available for trucks and cars by 2030.
Obama—Boost renewable fuel standard to at least 60 billion gallons of advanced biofuels like cellulosic ethanol by 2030; build out ethanol distribution infrastructure; mandate that all new vehicles be "flexfuel" by the end of 2012; produce 2 billion gallons of "cellulosic" ethanol from non-corn sources like switchgrass by 2013.
McCain—Favors ethanol incentives after opposing them in the past. Generally opposes subsidies and tariffs that distort marketplace.
Clinton—Wants to require U.S. utilities to get 25 percent of their electricity from renewable sources like wind and solar by 2025.
Obama—Backs 25 percent renewable requirement by 2025.
McCain—Opposed 2005 proposal for 10 percent requirement, emphasizes market choice.
Source: campaign Web sites