The summer of 2024 has officially become the hottest on record, marking a worrying milestone in a trend that scientists had long predicted. The intensifying heat and dryness, particularly in the Northern Hemisphere, have fueled severe droughts, heatwaves, wildfires, and crop failures across North America and Europe. These escalating conditions are increasingly threatening societies worldwide. A major contributor to these extreme weather patterns is the weakening of Earth’s air circulation systems, a phenomenon that scientists now attribute directly to human activities.
Two groundbreaking studies led by Dr. Rei Chemke of the Weizmann Institute of Science have uncovered the underlying cause of this weakening. Published in leading scientific journals, these studies reveal that manmade emissions of greenhouse gases such as carbon dioxide (CO2) and aerosols are the primary forces undermining the critical wind patterns that regulate global heat and moisture distribution.
Role of Storm Tracks and Hadley Circulation in Global Climate
The studies primarily focused on two crucial components of Earth’s air circulation: storm tracks and the Hadley circulation. Storm tracks, composed of high- and low-pressure weather systems, transfer heat, moisture, and momentum across the atmosphere, significantly influencing climate zones worldwide. The Hadley circulation, on the other hand, involves the movement of warm air from the equator to the poles and back again, maintaining climate stability across regions.
Both systems have been weakening for over 40 years. While the weakening of the Hadley circulation had previously been linked to human-induced emissions, the role of manmade activity in the weakening of storm tracks remained unclear until now.
Human Emissions Behind the Weakened Storm Tracks
In a study published in npj Climate and Atmospheric Science, Dr. Chemke, alongside Prof. Dim Coumou of Vrije Universiteit Amsterdam, identified that greenhouse gas emissions are responsible for weakening storm tracks. The research revealed that manmade emissions have caused warming at higher latitudes, which in turn has reduced the temperature difference between northern and southern regions a key driver of storm track intensity.
Dr. Chemke explained the consequences of this change: “Summertime storms play an important role in bringing cool air from the ocean to the land. Reducing their intensity can lead to increasingly extreme heat events.” This phenomenon helps explain why record-breaking temperatures were experienced on continents such as Europe and North America during the summer of 2024.
The study used vast amounts of climate data and advanced modeling to confirm that human emissions were the key factor behind the weakening of storm tracks. According to their findings, by the end of the century, the intensity of these summer storm tracks could decline by as much as 25 percent.
Hadley Circulation Reversal of Natural Trends
In a second study, published in Nature Communications, Dr. Chemke and his student Or Hess investigated the Hadley circulation and its historical changes. They found that over the past millennium, natural factors such as volcanic eruptions and solar fluxes had strengthened the Hadley circulation. However, in recent decades, manmade emissions have reversed this trend, causing the circulation to weaken instead of strengthen.
“The warming climate we see today due to human emissions is actively weakening the Hadley circulation,” said Hess. This weakening means that air is moving less efficiently from the equator to the poles, leading to more extreme weather conditions, particularly in subtropical and mid-latitude regions.
Surprising Impact of Natural Factors
While human activities are the dominant force driving current climate changes, Chemke and his team emphasized the ongoing importance of natural climate factors. Historically, natural phenomena like volcanic eruptions or solar changes significantly influenced Earth’s climate, and their effects continue to shape certain aspects of atmospheric circulation today. Although smaller in magnitude than human-induced changes, these natural forces still play a role in global climate systems.
“Our research shows that natural factors are often overlooked but can have a considerable impact on climate patterns,” said Dr. Chemke. “This was an important and unexpected finding for us, and it highlights the need for future climate models to better account for natural influences alongside manmade emissions.”
Dire Outlook for Future Summers
As the summer of 2024 draws to a close with record heat and alarming new data, scientists are warning that human-induced climate changes are here to stay, unless urgent action is taken. Both studies underscore that human activity has fundamentally altered Earth’s air circulation systems, intensifying heat events, droughts, and other climate-related disasters.
Without significant reductions in greenhouse gas emissions, researchers project that the weakening of storm tracks and the Hadley circulation will continue, further exacerbating the already catastrophic effects of climate change.
This summer’s extreme heat, which has placed millions of lives at risk, should serve as a wake-up call for global leaders and the public. Immediate action to curb emissions is not only necessary to halt these troubling trends but also to protect future generations from an increasingly uninhabitable planet.
Reference: https://www.preventionweb.net/news/how-humans-are-affecting-northern-hemispheres-wind-patterns