The Pacific Ocean might hold the key to a long-standing debate among climatologists.
The Pacific Ocean / © pexels.com
The Pacific Ocean could assist scientists in resolving one of the most complex enigmas in modern climatology. Recent research suggests that natural fluctuations in ocean temperatures might explain why climate models have yet to reach a consensus on changes in the Hadley circulation of the Southern Hemisphere.
This was reported by Earth.com.
Hadley circulation is a large-scale system of air movement within Earth’s atmosphere. Warm, moist air rises near the equator, travels in the upper atmosphere towards the subtropics, and then descends around 30 degrees latitude.
“Where this air descends, it dries the land beneath it, which is why the world’s major deserts are found around these latitudes. The surface flow returning to the equator becomes the trade winds,” the article states.
According to fundamental principles of climate physics, as greenhouse gases accumulate and the planet warms, the temperature difference between the tropics and the poles should decrease. Consequently, the Hadley circulation should gradually weaken. However, observations from recent decades indicate a strengthening of the southern part of the Hadley circulation.
It is this discrepancy that scientists, led by atmospheric researcher Mahdi Hassan from North Carolina State University, decided to investigate. The researchers focused on why climate models offer differing projections for the future of the southern Hadley circulation. While most models predict a weakening of the system for the Northern Hemisphere, the results for the Southern Hemisphere remain ambiguous, with some models showing strengthening and others showing weakening.
To examine the role of natural processes, the researchers ran the same climate model 50 times. In all instances, identical data on greenhouse gas emissions were used, but the initial conditions were varied.
During their analysis, the scientists discovered that the tropical Pacific Ocean might play a crucial role. The study indicated that changes in its surface temperature are linked to the behavior of the southern Hadley circulation.
The findings also revealed an unexpected characteristic. Two distinct types of oceanic changes can lead to an intensification of the circulation. The first is a uniform warming of the tropical Pacific Ocean. In this scenario, the ocean heats the air above it, increasing energy input to the circulation.
The second mechanism involves an uneven distribution of temperatures. If the southern part of the tropical Pacific becomes cooler than the northern part, a thermal imbalance occurs. The atmosphere responds by transferring energy across the equator, which also leads to an intensification of the circulation.
The authors of the study note that prolonged natural fluctuations can appear similar to trends associated with human activity. This is precisely why distinguishing the impact of natural processes from the consequences of global warming is not always straightforward.
The researchers concluded that natural variations in the tropical Pacific Ocean are a primary reason why the recent history of the southern Hadley circulation does not align with the expected impact of greenhouse gases. Furthermore, both oceanic warming and cooling can contribute to the strengthening of the circulation.
Scientists believe that incorporating natural fluctuations in the Pacific Ocean could improve precipitation and drought forecasts for the Southern Hemisphere. This is particularly important for Australia, Southern Africa, and parts of South America, as the Hadley circulation influences the aridity of these regions.
“Anyone tracking the past or future of this loop must now weigh the Pacific’s own rhythms, not just human influence. If done correctly, this could refine predictions for the rains and droughts upon which the Southern Hemisphere depends,” the article stated.
Previously, scientists recorded an anomalous “cold spot” in the North Atlantic, which may indicate an impending critical shift in ocean currents and could lead to severe climatic consequences for Europe.
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