NEW YORK (Reuters) - U.S. emissions of gases blamed for warming the planet rose 1.4 percent last year as acute weather pushed consumers to crank up heaters and air conditioners and cut output from hydropower generation, the federal Energy Information Administration said on Wednesday.

Century City and downtown Los Angeles are seen through the smog December 31, 2007. REUTERS/Lucy Nicholson

The rise in the pollution level made President elect Barack Obama’s goal of cutting U.S. greenhouse gas emissions to 1990 levels by 2020 more ambitious.

U.S. emissions last year were about 16.7 percent above 1990 levels, or a rise of 1.7 percentage points from 2006, the EIA said.

Obama also wants to cut emissions in the United States, the world’s top greenhouse gas polluter after China, 80 percent from 1990 levels by 2050.

U.S. greenhouse gases last year rose to 7.282 billion metric tons of carbon dioxide equivalent, mostly on a rise in emissions from the burning of fossil fuels, the EIA said.

Annual emissions from the globe’s biggest polluters are being closely watched as world delegates meet in Poznan, Poland this month as part of a push to agree to a pact to succeed the Kyoto Protocol, which expires in 2012, by the end of next year.

The United States was alone among industrialized countries in not ratifying the Kyoto pact, which requires 37 rich countries to cut emissions as a first step in reducing the chances of stronger storms and more heat waves, floods and droughts.

The EIA report showed the impact that weather can have on annual emissions as milder temperatures in 2006 led them to fall slightly, said EIA spokesman Paul McArdle.

He added that achieving Obama’s emissions goals would be a “substantial task.”

The EIA has projected in previous reports that U.S. energy-related emissions of the main greenhouse gas carbon dioxide, would rise an average annual rate of 0.5 percent from 2005 to 2030 in a business as usual scenario.

U.S. hydropower output dropped 14.2 percent last year which led to greater reliance on fossil fuels like natural gas and coal for power generation, the report said. Droughts in the U.S. Southeast and in California pushed down output from the source that is nearly emissions free.

The emissions intensity of the U.S. economy, or the volume of emissions for every dollar of economic output, fell by 0.6 percent in 2007, the smallest annual improvement since 2002, it said.

President George W. Bush has not agreed to mandatory emissions cuts. Instead, he set a goal of reducing emissions intensity by 18 percent over 10 years. Since 2002, the base year of that plan, U.S. greenhouse intensity has fallen by an average of 2.1 percent per year.