"Across the United States, scientists, CEOs, environment groups, state governments, and members of Congress are seeking a comprehensive approach to global climate change and what the President is proposing is really only a very small step in that direction; his plan only affects the transportation sector, which accounts for roughly one-third of US greenhouse gas emissions; and it is unclear how real this commitment is.
If we hope to deal with climate change in a reasonable manner, we need an approach that is both economy-wide and mandatory, and that will put us on a path toward significant greenhouse gas reductions."
We welcome the President's mention of climate change in the State of the Union address, but his commitments fall short of actually reducing greenhouse gas emissions.
The plan to reduce gasoline use by 20% comes from the following two measures:
1) Fuel standards calling for 35 billion gallons of renewable and alternative fuels (15%); and
2) Reforms to the Corporate Average Fuel Economy standard for cars (5%).
The overall 20% improvement claim is based on projected future gasoline use--not a reduction from current levels.
The increase in renewable fuels could provide a push for some climate-friendly alternative fuels; however, less GHG-friendly alternatives can also be used, leaving the climate benefits uncertain.
The proposed 5% reduction in gasoline use (to achieve the 20% goal) is based on an improvement in current CAFE of 4% per year (roughly 1 mile per gallon per year). However, the President's proposal does not commit to a new fuel economy standard for cars. He asks Congress to give the Administration authority to revisit the automobile standard but not to specify an actual numerical target.
At best, these two measures taken together could slow or stop expected growth in emissions from the transportation sector*, which represents roughly 1/3 of U.S. greenhouse gas emissions. No specific proposals were offered to deal with emissions from other key sectors such as electricity generation, manufacturing, or buildings. Given all of the calls for action from CEOs, religious leaders, state and local governments, and the general public, it's unfortunate that the President missed this opportunity to outline a meaningful, comprehensive proposal to deal with climate change.
View a chart of climate legislation  recently proposed in the Senate (pdf).
Read the Pew Center's recommendations for U.S. climate policy:
Agenda for Climate Action .
Read about the new coalition of businesses and NGOs calling for national legislation to reduce greenhouse gas emissions, United States Climate Action Partnership. 
*The White House Policy Initiative Twenty in Ten: Strengthening America's Energy Security  notes that "The President's plan will help confront climate change by stopping the projected growth of carbon emissions from cars, light trucks, and SUVs within 10 years."