Writer and environmental activist Bill McKibben urged Vermont lawmakers Wednesday to pass a big expansion of weatherization programs and block tar sands oil from being shipped on a pipeline that crosses northern Vermont. Speaking to a joint session of the Legislature, McKibben warned that the planet is warming rapidly and that steps need to be taken immediately to slow or reverse the trend. He said failure to act will bring more frequent storms like Tropical Storm Irene, which wreaked havoc on Vermont in late August 2011.