Times (UK): Expectations of what can be achieved by the United States in fighting global warming are unrealistic, climate change negotiators from more than 170 countries have been told. Hopes raised by a new willingness in the White House to take action to control climate change must be balanced by a realisation that there are limits to what the US can do, they were told. Todd Stern, President Obama’s special envoy on climate change, moved to play down hopes as the US joined UN talks on …