Rains in Republika Srpska: The state will still experience many extreme events, say Brazilian scientists who collaborated with the Intergovernmental Panel on Climate Change

“Unfortunately, I think there is a very high probability that these events will occur again in a more frequent and intense manner,” he says.

The Intergovernmental Panel on Climate Change is a group of scientists designated by the United Nations that monitors and evaluates science related to climate change.

In its report, the Intergovernmental Panel on Climate Change points to the human contribution to increased rainfall in the region called Southeastern South America (SES), which includes not only Rio Grande do Sul, but also other states in the southern region of Brazil and some regions of Brazil. . Countries such as Argentina and Uruguay.

The SES is the only one that includes Brazil where the Intergovernmental Panel on Climate Change has found evidence of heavy rainfall linked to human action.

The committee rates its conclusion as “low confidence”, but according to Krug, this is the highest level of evidence currently available for the region due to the difficulty of the calculations involved.

Mercedes Bustamante, a professor at the University of Brasilia (UnB) and a collaborator on some of the IPCC reports, also sees strong evidence of the impact of human-induced climate change on the rains, which caused 83 deaths and affected 345 of the country’s 497 municipalities. The country. Rio Grande do Sul.

According to the ecologist, member of the Brazilian Academy of Sciences (ABC), Rio Grande do Sul has always been a meeting point of tropical systems and polar systems, creating a pattern that includes periods of heavy rain and others of drought.

The tendency is for this alternation to continue to be repeated but with increasing intensity.

“This is an area where we will see more extreme events, according to climate models,” the expert says.

The heavy rains currently hitting Rio Grande do Sul can be explained by a combination of risk factors, including a mass of hot air over the central region of the country, blocking the cold front in the southern region and causing instability over the state. This caused heavy and continuous rain.

In addition, the period between the end of April and the beginning of May 2024 is still affected by the El Niño phenomenon, which is responsible for increasing the temperature of the waters of the Pacific Ocean, and also contributes to areas of instability over the country.

This combination of several factors at once is considered rare by experts.

However, according to Mercedes Bustamante, the greater frequency of these “combined risks” has been highlighted in the compilation of data on climate change by the Intergovernmental Panel on Climate Change.

“There is a convergence of different variables that act synergistically and increase this risk factor,” he says. “Many discussions about preparedness have been about risks in isolation, but we need to look at cascading impacts and risks in an integrated way.”

Bustamante explains that widespread deforestation in the Cerrado region in recent decades has led to higher surface temperatures and reduced the amount of evapotranspiration, or water returning to the atmosphere, in the central region of the country.

As less moisture returns, it becomes hotter and drier. In conjunction with the El Niño phenomenon, it is this hot air mass that blocks and maintains the zone of instability over Rio Grande do Sul.

“There is a regional phenomenon, which is El Niño, but it is also a problem related to the shift of our biomes,” he says.

At the same time, this same mass of hot air obscures the Amazon’s so-called “flying rivers”, a kind of invisible waterways that circulate through the atmosphere. This is the moisture generated by the Amazon region and spread throughout the South American continent.

If this watercourse finds a less dry environment in the central region of Brazil, part of it will be deposited there. But under current conditions, moisture is forced to shift around the edges of the hot, humid mass, hitting the Andes and moving south of the country.

“We had cold fronts that were not able to ‘rise’ and masses of moist air that were not able to spread into central Brazil and ‘leak’ to the sides,” he sums up.

According to the researcher, this context made the rains recorded last week more intense and widespread than those that struck Rio Grande do Sul in September 2023.

At the same time, according to Thelma Krug, there is growing evidence in science linking climate change to longer-lasting and more intense periods of El Niño.

“We actually saw El Niño extending over a longer period of time last year,” he says.

“And now we have a combination of very hot days with impacts on ocean surface temperature, which is the scenario that has an impact on all this change in terms of precipitation.”

According to the mathematics, it is very difficult to link human actions to heavy rainfall – unlike heat waves, which are more easily linked to human-induced climate change.

“But what we know unequivocally is that human impact has warmed the entire climate system: it has warmed the oceans, it has warmed the atmosphere, it has warmed the cryosphere. In other words, all the elements of the terrestrial biosphere,” she said. He says.

“It is impossible not to imagine that this warming that has affected the entire climate system will not have consequences in many areas.”

Krug and Bustamante were unequivocal in pointing out the need for appropriate adaptation measures for new climate models to avoid new tragedies in cases of future extreme events.

“Brazil needs to expand the environmental data monitoring network,” highlights the professor at the University of Brasilia.

According to Mercedes Bustamante, the risk maps prepared by the National Center for Monitoring and Warning of Natural Disasters (Simaden), linked to the Ministry of Science, Technology and Innovation, were created after the climate tragedy that left more than 900 people dead in the mountainous region. The Rio de Janeiro conference in January 2011 It needs to be reconsidered.

For Thelma Krug, planning must take place at the federal, state and municipal levels and supported by public-private partnerships.

“The frequency of these events in Rio Grande do Sul and the intensity of what is currently happening – which may be one of the largest in the country – is alarming and requires us to take action not only to resume life, but also to return to living in a different way,” he says.