Agence France-Presse: The US Senate may take up legislation crafting a “cap-and-trade” system for fighting climate change in as little as three weeks but surely by the end of the year, a key lawmaker promised Tuesday. Democratic Senator Barbara Boxer, who chairs the Senate Environment and Public Works Committee, said she would take the time necessary to build maximum support among her colleagues for swift and comprehensive action. “It will take a while, it could be weeks not months, but it will be …