> FAQ 2.1: The Earth’s temperature has varied before. How is the current warming any different?<p>> Earth’s climate has always changed naturally, but both the global extent and rate of recent warming are unusual. The recent warming has reversed a slow, long-term cooling trend, and research indicates that global surface temperature is higher now than it has been for millennia.<p>> It’s warming rapidly ...during the shift from the last glacial period to the current interglacial, the total temperature increase was about 5°C. That change took about 5000 years, with a maximum warming rate of about 1.5°C per thousand years, although the transition was not smooth. In contrast, Earth’s surface has warmed approximately 1.1°C since 1850–1900 ...for the past 2000 years, we have higher-resolution records that show that the rate of global warming during the last 50 years has exceeded the rate of any other 50-year period.