A new study has revealed yet another way that human-induced climate change is affecting the planet. Decades of weather balloon and satellite data has shown that the Earth’s troposphere is expanding, even after natural variations are accounted for.
The troposphere is the lowest layer of the Earth’s atmosphere, extending from the land and sea surface to a height of around 6 km (3.7 miles) above the poles and 18 km (11.2 miles) above the tropics. It’s the warmest and wettest layer – air gets colder and drier the higher you go – and it’s where most weather events play out.
It’s been known since the mid-2000s that the troposphere is expanding. As this lower layer warms up, it pushes upwards a boundary called the tropopause, which separates the troposphere from the higher, cooler stratosphere. A whole host of natural processes affect this layer, but of course, warming from carbon dioxide emissions is a key driver of the rise.
So for the new study, the researchers investigated how fast the tropopause was rising, and whether that had changed over time. And sure enough, they found that it was rising by about 50 to 60 m (164 to 197 ft) per decade over the last 40 years – at least, within the Northern Hemisphere.
The team used two main sources of data: radiosonde measurements from weather balloons, and GPS radio occultation data from satellites. The record of the former stretches as far back as 1980, while the latter chips in data after 2002, allowing the team to build a picture of the tropopause’s altitude between 1980 and 2020.
To check how much influence human activity was having on the tropopause rise, the team adjusted for natural events that are known to have an impact, including two volcanic eruptions in the 1980s, and a strong El Niño event in the late 1990s. When these were accounted for, they found that the majority of the rise – up to 53 m (174 ft) per decade – could be attributed to human-induced climate change.
“This is an unambiguous sign of changing atmospheric structure,” says Bill Randel, co-author of the study. “These results provide independent confirmation, in addition to all the other evidence of climate change, that greenhouse gases are altering our atmosphere.”
The team says that while a higher tropopause might not be too much to worry about in everyday life, it could increase the severity of thunderstorms, and require planes to fly higher to avoid turbulence.
The research was published in the journal Science Advances.
