Division on Earth and Life Studies

“How do we know that Earth has warmed? Scientists have been taking widespread measurements of Earth’s surface temperature since around 1880. These data have steadily improved and, today, temperatures are recorded by thermometers at many thousands of locations, both on the land and over the oceans. Different research groups, including the NASA Goddard Institute for Space Studies, Britain’s Hadley Centre for Climate Change, the Japan Meteorological Agency, and NOAA’s National Climatic Data Center have used these raw measurements to produce records of long-term global surface temperature change (Figure 1). These groups work carefully to make sure the data aren’t skewed by such things as changes in the instruments taking the measurements or by other factors that affect local temperature, such as additional heat that has come from the gradual growth of cities.”
― Division on Earth and Life Studies, Climate Change: Evidence, Impacts, and Choices