As atmospheres move heat, measurements capture different traces
Measurements from western Europe, Hong Kong and Venus show how atmospheric motion becomes visible through heat readings and estimates of planetary rotation at very different scales.
Science··Midday
A two-month average drew a broad heat picture
The Copernicus Climate Change Service measured the combined June and July temperature in western Europe at 21.62 degrees Celsius. That was 2.79 degrees Celsius above the 1991–2020 average and higher than the previous peak in 2022. Globally, July was jointly the second-warmest July at 16.90 degrees Celsius, 1.47 degrees Celsius above the 1850–1900 baseline. The extra-polar sea surface between 60 degrees south and 60 degrees north also averaged 20.96 degrees Celsius, exceeding the 20.89 degrees Celsius measured in July 2023. These figures describe a much wider area and a longer interval than one station's immediate weather. The same monthly picture included Arctic sea-ice extent at the sixth-lowest level for July and Antarctic extent at the fifth-lowest. Those indicators place the temperature measurements alongside changes registered over ocean and ice. Samantha Burgess of the service described July as the third consecutive month of exceptional heat in western Europe. Together, the land, ocean and ice observations show how a broad climate assessment is assembled from measurements with different geographical reach.[1]
In Hong Kong, hot air appeared station by station
The Hong Kong Observatory's headquarters reached 36.9 degrees Celsius on Sunday, moving above the 36.6 degrees Celsius measured there on 22 August 2017 before Typhoon Hato. At Sheung Shui in the north of the territory, the temperature reached 39.8 degrees Celsius, the highest in that series since automatic weather stations came into use. The Observatory linked the heat to warm air circulating ahead of the approaching Typhoon Dolphin, issued a very hot weather warning and expected extreme heat through Tuesday. The immediate explanation is meteorological: air descending on the outer flank of a tropical cyclone compresses, clears cloud and adds heat at the surface. A station high therefore does not by itself establish a long-term trend. The earlier headquarters mark was also recorded as a typhoon approached. Set beside a regional average, the Hong Kong readings offer a narrower view of heat: they show how a particular circulation pattern can raise temperatures at a specific place and time, while retaining the limits of what one station can say.[2]
On Venus, wind can look like planetary rotation
Stephen Kane of the University of California, Riverside uses Venus as a warning about measurement. The planet's solid surface completes one rotation in 243 Earth days, while its upper atmosphere circles the world in about four. When astronomers cannot see the surface of a distant planet directly and instead track light from its atmosphere, they may measure wind speed rather than the body's rotation. In the Venus example, that would make the planet appear roughly 60 times faster than it is. Kane proposes observing the same world at several wavelengths. Infrared bands that reach deeper atmospheric layers could help build a wind profile because winds on Venus slow toward the surface, separating atmospheric motion from the solid body's spin. This research does not explain hot weather in western Europe or Hong Kong, and it does not establish a causal link between terrestrial weather and Venusian rotation. The connection among the reports is narrower: depending on the scale and target of an instrument, atmospheric motion can leave a trace in a regional temperature average, a local station high, or the apparent rotation of a distant planet. The word atmosphere therefore covers three distinct physical settings whose measurements cannot be treated as interchangeable.[1], [2], [3]
