Climate change and pandemic disease are as serious a risk to international security as terrorism, and Britain must radically improve its defenses against a host of threats, Prime Minister Gordon Brown said Wednesday. Outlining the first major overhaul of homeland security since the end of the Cold War, Brown ranked extreme weather, potential flu pandemics and failed states alongside bombing attacks as the most serious threats to peace in Britain. "The nature of the threats and the risks we face have - in recent decades - changed beyond recognition and confound all the old assumptions about national defense and international security," Brown told lawmakers in the House of Commons. He said the greatest threats to Britain were "war, terrorism and now climate change, disease and poverty - threats which redefine national security." A classified list of threats to national security - which grades the level of risk from each category - will be released to the public later this year, he said. It is likely to confirm Britain now ranks climate change and pandemic disease as seriously as terrorist attacks, officials said.