Global Temperature Record
Guy Callendar averaged weather-station readings from around the world in 1938 and found about 0.3 °C of warming in 50 years; later datasets made this the yardstick of climate change.
Open in the interactive tree →Callendar averaged readings from 147 stations by hand; his result is close to modern estimates, though it covered only land between 60° south and 60° north. In 1986 Jones, Wigley and Wright combined land and sea data into the first comprehensive global estimate, and Hansen's method, documented in 1987, became NASA's GISTEMP record; NASA, NOAA, the UK's HadCRUT and Berkeley Earth now keep records back to the 1850s-1880s. This record is what the 1.5 °C goal of the Paris Agreement is measured against: the WMO put 2024 at 1.55 °C (plus or minus 0.13) above 1850-1900.
Prerequisites
- Statistics & Least Squares1809Turning thousands of readings into one average needs statistics.
- Weather Maps and Services1854Weather services built the worldwide network of station readings.
- Greenhouse Effect1896Callendar linked the warming to extra CO2 from burning fuel.
Unlocks
- IPCC Climate Assessments1988The IPCC reports start from the observed global warming in this record.
- Paris Agreement: 1.5 °C Exceeded2024The 1.5 °C goal is measured as a rise in the global temperature record.
- Climate Sensitivity RangeopenClimate sensitivity is estimated by comparing observed warming with the forcing.