Environmentalists had good reason to feel optimistic after it became clear that Barack Obama and John McCain, the two US senators, had won their party’s presidential nominations for the elections in November.

For activists frustrated by nearly eight years of inaction by the Bush administration on global warming, both candidates represent a radical departure from the status quo. Though details of their proposed plans differ, both Mr McCain, the Arizona Republican, and Mr Obama, the Democrat from Illinois, have vowed that, if elected, they would take action on global warming and support legislation to create a cap-and-trade system to regulate and reduce carbon emissions.