The phrase "to cool the earth" means to reduce the overall temperature of the planet, often by taking actions to decrease global warming and combat climate change. Full definition
Love the feeling of spring time cool earth between my toes and late nights at music festivals. (datingforhippies.com)
This temperature contrast makes for more high intensity storms, which leads to more atmospheric dust and sea salts, which reflects more sunlight back into space and cools the earth further. (williamcalvin.com)
Basic physics is at work: normally, daily evaporation of moisture from soil cools earth's surface. (ldeo.columbia.edu)