This article Reprinted from conversation Under Creative Commons License.
Last week, the record for the hottest day on Earth was broken twice. Sunday, July 21, was declared the hottest day since records began, when the average surface temperature reached 17.09°C. On Monday, the record was broken again. The average temperature reached 17.16 degrees.Tuesday was almost as hot.
The declaration was published by Copernicus, the European climate change service, and is expected to be released in the coming days, especially in the Northern Hemisphere. Extreme heat.
Determining the Earth’s average temperature on any given day is a complex task, requiring thousands of observations using high-tech instruments and sometimes sophisticated computer models.
So let’s take a look at how scientists measure Earth’s temperatures and what these broken records mean.
How to know if it’s hot
Earth’s average surface temperature is the main indicator used to track how the climate is changing and is the measure used in the Paris Agreement.
It is derived from a combination of both the average temperature of the air just above the earth’s surface and the air over the ocean.
In addition to Copernicus, estimates of the Earth’s average surface temperature have been calculated using a variety of methods. National Organization In America, Englandand Japan.
All of the data sets produced by these agencies show a very clear warming trend since 1900.
Most datasets are directly Observed temperature Temperature measurements from land-based weather stations and floats at sea are equipped with thermometers, and satellites in space are also used to gather infrared estimates.
With the advanced methods and thousands of observations in use today, daily temperature data are much more accurate than in the past. The further back in time we go, the more uncertain our estimates of the Earth’s average surface temperature become.
What is Copernicus?
of Copernicus Climate Change Service It is part of the European Union’s Earth Observation Programme. Copernicus uses not only observations but also Computer model simulation.
The model simulates temperatures 2 meters above the surface anywhere on Earth. The results are: Average ocean surface temperature It is derived from direct observations and satellite information.
Copernicus uses information from model simulations, so its methodology is slightly different to other data sets, but the method is highly regarded and provides estimates of the average surface temperature across the globe within a few days.
Unlocking Temperature
We know the climate is changing rapidly, but why are we experiencing these record-breaking heatwaves now?
As the graph above shows, the Earth’s average surface temperature follows a clear seasonal cycle: July temperatures are typically about 4 degrees warmer than January.
This difference is due to the larger land area of ​​North America, Europe, and Asia compared to the Southern Hemisphere.
