No, climate change is definitely not a hoax. There is substantial evidence of climate change occurring globally. In order to view how the climate and temperatures of Earth have changed, scientists record previous ice, sediments, cave formations, the coral reef, and tree rings. Researchers and scientists can look for chemical signals within observations, such as Carbon Dioxide trapped inside glacial ice. In this scenario, it can prove the atmospheric conditions of the past. Fossilized pollen has been studied to determine the vegetation that thrived in a particular area. Tree rings can be used to figure out the season-by-season record of temperatures and moisture of certain areas and climates. Lastly, the observations of oxygen variants of coral reefs can help scientists establish the precipitation in that area and time period.