How human activity weakens the natural "ventilation systems" of the earth
The summer of 2024 was the hottest since temperature measurements began in Israel. This is not a one-off event: in many places in the Northern Hemisphere, the summer season becomes hotter and drier year after year, which leads to heat waves and severe droughts and increases the risk of fires, damage to agriculture and health hazards. Climate researchers know that one of the main causes of these phenomena is the weakening of the "ventilation systems" - the air flow patterns in the atmosphere that are responsible for distributing heat and moisture around the globe - but they do not know what the exact reasons for this weakening are. Now, two studies led by Dr Rai Chamka The Weizmann Institute of Science sheds some of the mystery on the subject - even if not the heat and humidity - and shows that increased human activity leads to the weakening of two of the natural ventilation mechanisms in our world.
The first study that Dr. Chamka carried out in collaboration with Prof. Die Comeau from the Institute of Environmental Studies at the Free University of Amsterdam, dealt with the summer storms in the Northern Hemisphere - those weather systems of high and low atmospheric pressure that progress from west to east. These storms have a considerable cumulative effect on the movement of heat, moisture and air in the atmosphere and on the determination of the different climate zones on the planet. "Summer storms play an important role in bringing cold air from the ocean to the land. When their intensity decreases - less cold air arrives, the temperatures rise and with it the frequency of extreme heat events", explains Dr. Chamka.
in the findings which were published in the scientific journal npj Climate and Atmospheric Science The researchers showed for the first time that these storms are weakening as a result of emissions originating from the human activity of the last decades. To reach these findings, the scientists analyzed huge amounts of climate data, which were based on a combination of observations and advanced climate models. "The emissions cause a greater increase in temperatures near the poles, and as a result, the temperature gap between the northern and southern latitudes is reduced," Dr. Chamka explains the mechanism. "Since the temperature difference is the cause of the formation of the storms in the first place, its reduction leads, directly, to their weakening."
There is a hole in the head
The second study dealt with the bucket cell - a cyclic air circulation system, which transports heat and moisture between the different latitudes and thus plays a central role in the distribution of rain and in determining the climate zones on the planet. In a study published in a scientific journal Nature Communications. Dr. Rei Chamka and research student Or Hess asked to understand the changes in the air flow in the bucket chamber along the timeline. "Since we have no documentation of the air flow in the last thousand years, it is not possible to simply go to the measurements and compare the patterns in the past with what is happening today," says Dr. Chamka. "But today there is certainly a good ability to reconstruct the factors that drive the climate system and use them to reconstruct the past climate with the help of models that preserve all the physics, biology and chemistry of the climate system."
With the help of the models, Dr. Chamka and Hess were able to trace how natural factors, such as volcanic eruptions or changes in energy flows from the sun, led to changes in the air flow in the bucket chamber in the previous centuries. In contrast to the ongoing weakening trend that we are dealing with today, the researchers discovered that in the last thousand years natural factors acted in a way that strengthened the air flow and that human emissions actually led to the reversal of the natural trend. "In the previous millennium, natural factors had the greatest impact on the bucket cell, today it is evident that human factors are more dominant," emphasizes Hess.
"Our field of research mainly deals with man-made emissions and the warming climate", concludes Dr. Chamka. "Therefore, there is less attention paid to the climatic effect of natural factors such as volcanic eruptions, changes in solar energy or natural emissions of greenhouse gases, but we have shown that natural factors can have a very significant effect on the climate, even if on a smaller scale compared to human activity. In the specific case of the Aquarius cell, the natural factors have an opposite effect to the human influence. These are very surprising findings, and more emphasis should be placed on them in the future."