Abholzung im Amazonasgebiet könnte die Häufigkeit von Gewittern in Südamerika verringern

Alles hängt irgendwie zusammen. Pressemitteilung der Tel-Aviv University:

Deforestation in the Amazon may be decreasing the frequency of thunderstorms in South America

For the first time, researchers from Tel Aviv University have determined that due to the ongoing deforestation in the Amazon basin in recent decades, the number of thunderstorms in the region has decreased significantly, and the area over which they occur has shrunk.According to the researchers, this is a surprising finding: “In most areas of the world, global warming has resulted in an increase in the number of thunderstorms, but in this study, we discovered that precisely in those areas where deforestation has increased the number of storms actually decreased, even with rising temperatures.”

“In addition, the rainforests themselves produce their own rain: the trees emit water vapor via evaporation into the air that eventually condenses and forms clouds and rain above the rainforests. Hence, the forests influence the local and regional rainfall.”

The researchers point out that these important processes are currently in danger due to the extensive activity of deforestation in the Amazon, i.e., cutting down trees for wood and clearing areas for agriculture, infrastructure development, mining, etc. In fact, in the 30 years between 1990 and 2020, forests whose total area is larger than the entire continent of Europe were destroyed in the Amazon basin.

To sum up, the destruction of rainforests impacts global oxygen levels while increasing the greenhouse gases in the atmosphere and disrupting natural rainfall patterns that may lead to further drought in some areas. In addition, the trees that have been cut down are often burned, releasing additional carbon dioxide into the air and contributing to global warming.

In this study, the first of its kind, the researchers sought to track changes in the extent of thunderstorms in the Amazon basin in recent decades. In the absence of thunderstorm data from the Amazon going back decades, the researchers built an empirical model based on climatic parameters from the European Center ERA5, which has collected data on global climate since 1940, along with thunderstorm data collected through a worldwide network of lightning detection sensors called WWLLN—the Worldwide Lightning Location Network.

Prof. Price explains, “Lightning is the result of a huge electric field that is discharged all at once, producing radio waves that can be received thousands of kilometers away. The sensors of the WWLLN network are deployed in 70 research institutions worldwide, and they receive and map, in real-time, lightning everywhere on the surface of the Earth.”

“Here at Tel Aviv University, on the roof of the Geophysics building, we have one of the sensors that pick up radio waves from thunderstorms that occur in our region, in Africa, India, and even South America. Cross-referencing the information from the various stations accurately determines the location and time of each lightning strike, and thus a global map of lightning strikes over time is obtained.”

Using the empirical model, the researchers examined the relationship between the frequency and distribution of thunderstorms in South America, and changes in temperature in the Amazon region since the 1980s. A statistical analysis of the data revealed surprising findings: despite the increase in regional temperature resulting from global warming, there was a decrease of approximately 8% in the number of thunderstorms over this period.

The researchers say, “When we examined these findings in depth, we discovered that the areas of decline in the number of thunderstorms overlap to a large extent with areas where extensive deforestation was carried out. This is the first time that a connection between thunderstorms and deforestation has been established.”

“We estimate that the loss of each megaton of carbon in the Amazon—equivalent to about a million large trees cut down—results in a 10% decrease in the number of thunderstorms.”

Prof. Price concludes, “In this study, we examined trends in thunderstorm activity in the Amazon basin in recent decades. We expected to find an increase in the number of storms due to global warming, as has been observed in many regions of the world, but to our surprise, we found the opposite trend: a decrease of 8% over 40 years.”

“Further analysis revealed that most of the decrease was observed precisely in those areas where the rainforests were replaced by agriculture or other human activity. The decrease can be explained by the fact that the absence of forests significantly reduced the moisture in the air, which is the source of energy and moisture needed for the formation of thunderstorms.”

“The result is fewer thunderstorms, fewer clouds, less rain, and consequently less forest growth. This creates a dangerous feedback loop that can cause the forests to dry out and significantly reduce the vital contribution of the ‘lungs of the Earth’ to oxygen production and carbon dioxide absorption.”

Paper: Raam Bekenshtein et al, Is Amazon deforestation decreasing the number of thunderstorms over South America?, Quarterly Journal of the Royal Meteorological Society (2023). DOI: 10.1002/qj.4518


Dazu passt diese AFP-Meldung (via phys.org):

Deforestation in Brazilian Amazon halved in 2023

Deforestation in the Brazilian Amazon fell by half last year, according to figures released Friday, as President Luiz Inacio Lula da Silva’s government bolstered environmental policing to crack down on surging destruction.


University of Copenhagen:

New study reports that Greenland is a methane sink rather than a source

Researchers at the University of Copenhagen have concluded that the methane uptake in dry landscapes exceeds methane emissions from wet areas across the ice-free part of Greenland. The results of the new study contribute important knowledge to climate models. The researchers are now investigating whether the same finding applies to other polar regions.

It has long been thought that the Arctic may be a ticking climate bomb. As local temperatures rise and permafrost thaws, more and more of the greenhouse gas methane is released. But in a new study from the Department of Geosciences and Natural Resource Management at the University of Copenhagen, researchers have been able to conclude that at least Greenland does not seem to be a methane bomb after all.

In fact, Greenland consumes more methane than it releases, according to analyses of soil samples from 11 areas across Greenland. The researchers used an existing dynamic methane model, which made it possible to quantify the methane budget for all of Greenland.

The researchers have been able to conclude that, on average and since 2000, dry landscapes of the ice-free part of Greenland have consumed more than 65,000 tons of methane annually from the atmosphere, while 9,000 tons of methane have been released annually from its wet areas.

“This is partly due to Greenland’s widespread dry landscapes, where methane from the atmosphere is consumed into the upper layers of soil, and partly because the ice-free parts of Greenland have only been without ice since the last ice age, meaning that they never stored much carbon, which could lead to large methane emissions, as can be measured elsewhere in the Arctic,” says Professor Bo Elberling, who led the study.

The research is published in the journal Communications Earth & Environment.

Microorganisms make methane uptake possible

The absorption of methane is made possible by a unique group of microorganisms that typically live in the upper half meter of arctic soil, where it is dry and oxygen is present. These microorganisms use methane that penetrates the soil from the atmosphere and convert it into carbon dioxide.

Although carbon dioxide is also a well-known greenhouse gas, its greenhouse gas effect is a lot less strong than methane, making the conversion of methane to carbon dioxide good climate news.

The study also provides knowledge about the optimal soil conditions for methane uptake in the Arctic. This is because the microorganisms require various nutrients and soil with just the right acidity (pH-level).

Researcher and first author of the article Ludovica D’Imperio elaborates, “Our work also sheds light on the conditions that, in addition to the climate, are crucial for methane uptake in Greenland. Based on our statistical model, we can conclude that it depends on the presence of the right microorganisms, soil acidity and copper—knowledge that we were previously uncertain about.”

Greenland’s methane budget

All in all, the new study demonstrates that Greenland contributes with a small uptake of methane under current conditions, which will most likely increase as Greenland’s climate changes in the future.

However, the conclusion is not that Greenland will impact the total global amount of atmospheric methane or prove to be decisive for Arctic methane budgets. The uptake of methane in Greenland is simply too small compared to other known methane sources, both in the Arctic and globally.

Indeed, the majority of Arctic wetlands, and thus the largest natural source of methane, are in Siberia. Until the war between Russia and Ukraine broke out, the Danish researchers conducted studies there alongside German and Dutch counterparts.

“We had just managed to demonstrate that methane uptake occurs in dry Siberian soils as well, but more studies will be needed in Siberia to provide a methane budget similar to what we now have for Greenland. Still, we have advanced considerably with similar studies in cold regions in Tibet, for example, where measurements indicate a similar conclusion as for Greenland.

“But the work has only just begun to understand the variation in this uptake of methane and its significance for the global methane budget,” says Elberling.

According to the researchers, the new study does not change the fact that greenhouse gas emissions from human activities must continue to be reduced. But the study does contribute previously unknown nuances of Greenland’s natural methane budget.

“Our research and that of others in the field helps to increase our understanding of the complex processes that are critical for the global methane budget. The budgets will be used both now and in the future to develop models that can provide a more accurate picture of the significance of global methane uptake,” concludes Bo Elberling.

Paper: Ludovica D’Imperio et al, Spatial controls of methane uptake in upland soils across climatic and geological regions in Greenland, Communications Earth & Environment (2023). DOI: 10.1038/s43247-023-01143-3 , www.nature.com/articles/s43247-023-01143-3