By Richard Somerville, Distinguished Professor Emeritus and Research Professor at Scripps Institution of Oceanography, UC San Diego, and Catherine Gautier, professor emerita at the UC Santa Barbara. As this is written, all four remaining candidates in the race for the Republican presidential nomination vehemently reject the fundamental findings of modern climate science. These findings are simple to state: The Earth's climate is now unequivocally warming. Many chains of evidence demonstrate the warming, including increasing atmospheric and ocean temperatures, rising sea levels, shrinking glaciers and ice sheets, and changing precipitation patterns. The main cause of the warming is human activities, especially burning fossil fuels, which increases the amount of heat-trapping gases in the atmosphere.