In the past week, Earth’s record for the hottest day was broken twice. Sunday July 21 was declared Earth’s hottest day since records began, when average surface temperature reached 17.09°C. On Monday the record fell again, when average temperatures reached 17.16°C – and Tuesday was almost as hot.
The declarations were made by Copernicus, the European climate change service. They made international headlines – especially in the northern hemisphere, which has been experiencing extreme summer heat.
Determining the global average temperature on any given day is complex. It involves thousands of observations using high-tech equipment and in some cases, sophisticated computer models.
So let’s take at look at how scientists take the planet’s temperature, and what these broken records mean.
The global average surface temperature is the main indicator used to track how the climate is changing, and the measure used under the Paris Agreement.
It is derived from a combination of both the average temperature of air just above the land surface and in the upper layer of the ocean.
Several organisations develop estimates of Earth’s average surface temperature using a variety of methods. Aside from Copernicus, they include national organisations in the........