July 10 (Bloomberg) -- European Union carbon dioxide permits had their biggest weekly gain in more than a month after nations agreed to take steps against climate change caused by heat-trapping gases.

EU carbon allowances for December rose 1.2 percent to 13.96 euros ($19.47) a metric ton on London’s European Climate Exchange as of 5:30 p.m., which would be the highest close since June 5. That took their weekly gain to 7.1 percent, the biggest jump since the week ended May 22.

The largest polluting countries yesterday agreed to limit world temperatures and set a global emissions goal for 2050 by December. The G-8 nations agreed for the first time to cut their greenhouse gas emissions 80 percent by 2050 and repeated a call for developing countries to accept a global reduction target of 50 percent by mid-century.

“Certainly the 80 percent commitment is a key building block for a global deal, but it is only part of the story,” said Richard Gledhill, global leader, climate change and carbon markets at PricewaterhouseCoopers LLP. “We also need ambitious mid-term targets, if we want to get onto a trajectory towards early stabilization,” of greenhouse gases, he said today in an e-mailed statement.

The European Union has said it will cut emissions by as much as 30 percent of 1990 levels by 2020.

U.S. President Barack Obama, who this week led a meeting of the world’s largest carbon emitters in L’Aquila, Italy, said “important strides” were achieved and all countries must work collectively to battle rising temperatures and sea levels.

“The rally is unwarranted,” Jan Pravda, director of Dublin-based emissions brokerage Carbon Warehouse Ltd., said today by phone. “The market seems to be allowing the politicians to take its eyes off 2020 goals.”

To contact the reporter on this story: Mathew Carr in London at m.carr@bloomberg.net

Last Updated: July 10, 2009 12:57 EDT