Temperatures on Earth vary from night to day and between seasonal extremes in the Northern and Southern Hemispheres, so the differences in the hottest and coldest places will always be large.
To calculate a global average temperature, measurements are taken all over the world. The measurements are compared, which makes it possible to form a detailed picture of local and global climate changes over time. Independent research groups around the world carry out their own analyses of the data. All indicate that we have a warmer climate than before.
