At a pair of international summits dealing with climate change this week, President Obama will be able to point to something no previous president has: a House-approved bill that would cap U.S. greenhouse-gas emissions. But he'll still hear the same criticism lobbed at his predecessors -- that America isn't doing enough. In L'Aquila, Italy, where the Group of Eight powers and a wider circle of 17 heavy-polluting nations will both meet, both environmental groups and European countries are likely to call the U.S. legislation insufficient. The House bill calls for a 17 percent reduction in U.S. emissions, as compared to 2005 levels, by 2020. These critics want cuts of 20 percent or more, and they want to use the more demanding baseline of 1990. 'The science, in our view, certainly demands more' than the U.S. bill, said Malachy Hargadon, counselor on the environment of the European Commission's delegation in Washington. So a measure hailed as a historic stride will be cast, three weeks later and 4,500 miles away, as a stutter-step -- and, in some places, a stumble. The reaction is one symptom of a growing alarm: six months before a key global meeting, there are still major disagreements among the players needed to tackle climate change. European countries 'have set a very high bar, and are coming to realize the U.S. is not going to meet it,' said Elliot Diringer, a vice president at the Pew Center on Global Climate Change. But he said that if they want the U.S. in an agreement, 'they'll have to find a way to accommodate the level of effort the U.S. brings to the table.' The meetings begin Wednesday with the three-day G-8 summit, at which leaders are expected to discuss climate change along with the global economy, financial regulation and security issues. It will mark an important first: Obama's debut in climate talks with world leaders, following a president that many blamed for inaction on the subject. That summit will overlap with a one-day meeting of the 'Major Economies Forum,' a climate-centered group whose members, including China, India, the U.S. and Brazil, account for 80 percent of the world's emissions. During the week, American and European negotiators may find common ground -- as long as they're talking about goals four decades away. Earlier this week, news reports indicated that European leaders want major emitters to set a goal of cutting global emissions 50 percent below 1990 levels by 2050. An Obama Adminstration official said yesterday that the U.S. supports a 50 percent cut, but it was unclear if the administration would seek a baseline year of 1990 or 2005. The near future is more of a problem. European Union countries have pledged to cut their emissions 20 percent below 1990 levels by 2020. In the U.S., the House bill uses 2005 as a baseline, which is a more lenient standard because emissions had grown by then. The House bill calls for emissions to be reduced from using a 'cap and trade' system -- in which factories, oil refineries, power plants and other polluters would be required to amass buyable, sellable credits for all they emit. Most European leaders have greeted this news with praise, for the bill's historic nature, if not for its exact details. But some environmental groups said they had expected far more. 'We are really disappointed, because we had great hopes for the Obama Administration,' said Sonja Meister, a spokeswoman for Brussels-based Friends of the Earth Europe. 'It's great that they're back' in serious climate talks, Meister said, but U.S. efforts on the climate 'don't really look much different than the (actions) of the Bush Administration.' The Obama administration isn't likely to promise major changes in short term goals. An administration official cited comments in May from U.S. climate envoy Todd Stern. Stern said, 'We are jumping as high as the political system will tolerate.' This kind of fundamental division over short term goals -- and another one, with developing countries like India and China demanding that developed nations shoulder the heaviest burdens of cutting emissions -- bogged down international climate talks in Bonn in June. If they do the same in Italy, environmentalists say, there will be even greater worries about major talks scheduled for December. In Copenhagen that month, world leaders are supposed to come up with a successor treaty to the 1997 Kyoto Protocol, describing how the world will work together to fight climate change. For now, U.S. officials are setting expectations for this week low: 'The goal itself is really to show forward momentum from what there has been,' the Obama Administration official said. 'There's no specifics.' 