Observations of the climate system are based on direct measurements and remote sensing from satellites and other platforms.
Global-scale observations from the instrumental era began in the mid-19th century for temperature and other variables, with
more comprehensive and diverse sets of observations available for the period 1950 onwards. Paleoclimate reconstructions
extend some records back hundreds to millions of years. Together, they provide a comprehensive view of the variability and
long-term changes in the atmosphere, the ocean, the cryosphere, and the land surface.