Chinese researchers believe that soil drought linked to climate change can no longer be offset by weather cycles. A challenge for the region’s crops and economy
by Matteo Cavallito
Agricultural drought that hit Central Asia two years ago is not an independent event but rather a symptom of a long-term trend that may find further confirmation in the future. This is supported by a study by the Institute of Atmospheric Physics (IAP) of the Chinese Academy of Sciences, which analyzed the trend and hypothesized its evolution in the coming years.
“Agricultural drought refers to soil moisture deficits, which is closely related to meteorological factor changes and usually happens after meteorological drought,” Jiang Jie, lead author of the research, said in a statement released by the Academy. According to the scientists, a decisive role belongs to the so-called anthropogenic external forces, that is, the set of human-led actions that, together with the natural variability of the climate system, have led to the intensification of this trend since the 1990s.
Human factor is crucial
Published in Nature Geoscience, the study was based on several experiments including observations and large-scale simulations provided by the U.S. National Center for Atmospheric Research, the Max Planck Institute in Munich, Germany, and Australia’s Commonwealth Scientific and Industrial Research Organization.
“The anthropogenic external forcing includes anthropogenic changes in greenhouses gases, aerosols, and land use, etc.,” Jiang explained.
Emissions, in particular, have caused rapid warming throughout Central Asia, leading to increased evaporation and a subsequent reduction in soil moisture. As well as notoriously promoting desertification. Added to this are the effects of a natural phenomenon known as IPO – Interdecadal Pacific Oscillation that impacts the temperature of the northern and southern waters of the ocean by following 20- or 30-year cycles.
Pubblicato su Nature Geoscience, lo studio si è basato su diverse sperimentazioni tra cui le osservazioni e le simulazioni di grandi dimensioni fornite dal National Center for Atmospheric Research degli Stati Uniti, dal Max Planck Institute di Monaco di Baviera, in Germania, e dalla Commonwealth Scientific and Industrial Research Organization australiana.
Weather cycles no longer offset climate change
In the so-called positive phases of the IPO, the surface temperature of the tropical Pacific is higher than average; the surface temperature of the northern part remains cooler. In the negative phases, the trend reverses: the northern seas warm while the southern seas experience a drop in temperatures.
Since the 1990s, sea surface cooling in the East-Central tropical Pacific has led to a reduction in spring precipitation in South-Central Asia leading to a drop in soil moisture at the beginning of the growing season.
The problem, the scientists notice, is that given human-caused global warming, future reversals in the IPO may not be sufficient to counterbalance the worsening drought over the century. Even a rise in sea temperatures in the tropical Pacific Ocean belt, in short, “could not counterbalance the human-induced drying trend over Central Asia,” pointed out Zhou Tianjun, professor and co-author of the research.
The consequences of drought
Agricultural drought is not the only issue. Also worrysome are the “increasing risks of meteorological drought and hydrological drought in southern Central Asia.” This calls for “developing a thorough risk-management plan at sectoral, local, country and even multi-country levels to adapt and mitigate the enhanced agricultural droughts for food security and livestock production.”
In Central Asia, agriculture and livestock are the sectors that contribute the most to GDP, the authors explain. Therefore, “The increasingly serious agricultural droughts not only directly influence crops and livestock but are also a challenge for production, living, ecological environments, social stability and even regional security.” An inevitable consequence of a phenomenon that cannot be stopped, “unless we take ambitious climate action and reach global peaking of greenhouse gas emissions as soon as possible to achieve a climate-neutral world.”