I argue that historic (Aristotle and Aquinas) and contemporary discussions of prudence and justice offer guidance for humanity mobilizing for climate security. Prudence has been held as the queen of the virtues because it guides decision and action. Justice too plays a unique role as it directs care due to others and to the common good. If prudence concerns can justify high military spending to protect a nation's security, surely prudence also requires nations to spend comparable sums on climate security. Justice concerns must shape the differential levels of climate security spending owed by different nations. Some island nations and poor countries need to receive climate change funds to help them adapt to climate change and to shift to build solar and wind power capacity. Wealthy nations and those most responsible for climate change must bear the heaviest burdens of mitigating climate change and helping other nations to adapt to new conditions. The United States offers an interesting case study. It is the wealthiest nation with annual military spending of roughly $1 trillion, more than the next 9 nations combined. The US is also the world's top climate perpetrator given its industrialization in the 19th century and its sustained high use of fossil fuels. National mobilization efforts for many nations hit their historic peak during World War II. US military spending rose to 40% of our gross domestic product (GDP). During much of the Cold War US military spending stood between 10-12% of GDP. My proposal is that the US commit a new annual climate security budget equal to our current military spending. Current US military spending is less than 4% of our current GDP. A new security line would push total US security spending to 8% of GDP. This is well under the level of US security spending during the Cold War. Any US climate security efforts, like those of all other nations, directly support the common good of the entire Earth community.