This Commentary discusses the CO2 footprint of California’s drought during 2012–2014. We show that California drought significantly increased CO2 emissions of the energy sector by around 22 million metric tons, indicating 33% increase in the annual CO2 emissions compared to pre-drought conditions. We argue that CO2 emission of climate extremes deserve more attention, because their cumulative impacts on CO2 emissions are staggering. Most countries, including the United States, do not have a comprehensive a nationwide energy-water plan to minimize their CO2 emissions. We argue that developing a national water-energy plan under a changing climate should be prioritized in the coming years.