In January 2020, overwhelming floods devastated several cities in Minas Gerais, causing massive damage and even death. A study published this week in the journal Climate Resilience and Sustainability indicates that the strong chuvas that caused the floods are more than 40% related to climate change on the planet.

Making use of climate modeling, the research shows that the effects of industrialization and global warming increased the probability of much higher rainfall volumes than expected in the region by 70%, compared to scenarios with average temperatures of 1°C to 1,1°C lower.

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Flood in the city of Guarani, southeast of Minas Gerais. Image: Ronaldo Almeida – Shutterstock

According to the Phys website, the study's authors also quantified the damage caused by the extreme event, estimating that more than 90 people were temporarily homeless and more than R$1 billion were lost in the public and private sectors. 

Most of the material damage was to public infrastructure (R$484 million), housing (R$352 million) and retail stores and other services (R$290 million). Human-induced climate change accounts for 41% of the total.

A week before the publication of the study, the Intergovernmental Panel on Climate Change (IPCC) emphasized in its sixth assessment report that “it is unequivocal that human influence has warmed the atmosphere, ocean and Earth, contributing to rapid and intense changes in all the regions of the planet”.

Minas Gerais capital had the wettest period in its history

The extreme rainfall event that occurred in Minas Gerais from January 23-25 ​​last year, which led to flooding and landslides, resulted from an intensification of the South Atlantic Convergence Zone (SACZ) combined with the emergence of the cyclone subtropical Kurumí (KSC) over the South Atlantic. Both phenomena increased the moisture content throughout the region.

Belo Horizonte had the wettest January in its history. According to the National Institute of Meteorology (INMET), rainfall totaled 935,2 mm, almost triple the monthly average, with 320,9 mm falling in just three days. At least 56 deaths were caused due to floods and landslides at the time.

According to its authors, the study offers new directions on the urgent need for action on climate change, which is already having a significant impact on the Brazilian Southeast: "This requires immediate improvements in strategic planning with a focus on mitigation and adaptation", he says. the article, adding that public management and policy must evolve from disaster response to include the prevention of future tragedies. 

House collapses in the municipality of Raul Soares, in Zona da Mata, Minas Gerais. Image Reproduction Social Networks via G1

Funded by the Foundation for Research Support of the State of São Paulo (FAPESP), the study derived from a workshop given, among others, by Sarah Sparrow, researcher at the University of Oxford (United Kingdom) and co-author of the article. The workshop was sponsored by the Brazilian arm of the Climate Science for Service Partnership (CSSP Brazil – Service Partnership for Climate Science, in free translation), a collaboration between UK institutions and organizations in Brazil, such as the National Institute for Space Research (INPE). ), the Center for Natural Disaster Surveillance and Early Warning (CEMADEN) and the University of São Paulo (USP).

Held online in December 2020 in partnership with Liana Anderson, CEMADEN researcher and also co-author of the article, the workshop discussed a method known as extreme event attribution that aims to quantify the potential effects of human-induced climate change on the probability of extreme events weather.

Two working groups analyzed the extreme precipitation event in Minas Gerais. One focused on the influence of climate change on rainfall, while the other quantified the impacts on the population. The conclusions of both groups were integrated into the published article.

“The close interdisciplinary collaboration allowed us to produce a high-quality study with consistent results in just a few months,” said Ricardo Dal'Agnol, a researcher at INPE's Earth Observation and Geoinformatics Division and the main author of the article.

Flood in Manhuaçu left much of the city under water in 2020. Image: Teo Nazaré – Jornal Comunhão

The global climate model used for attribution was the Hadley Center Global Environmental Model version 3-A (HadGEM3-A), with simulations of extreme weather events. 

Two experiments were conducted to help design scenarios, one considering only natural factors, such as variations in solar irradiance and volcanic activity, and the other also considering anthropogenic factors, such as land-use changes and emissions. greenhouse gases compared to the pre-industrial level.

According to the latest IPCC report, the planet's average temperature is 1,1°C higher than between 1850 and 1900, a reference period used to approximate pre-industrial temperatures before the sharp increase in gaseous emissions greenhouse, such as CO2 and methane.

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Research divided the state into 12 mesoregions

To understand the spatial distribution of daily precipitation in the study area and estimate precipitation for the attribution analysis, the researchers used the CPC Global Unified Meter-based Daily Rainfall Analysis and the Climate Hazards Group Infrared Rainfall with Station Data (CHIRPS ), which integrates satellite imagery and rainfall station data to create time series for trend analysis and monitoring.

Disaster data, including location, type, causes and damage, were extracted from Brazil's S2iD Integrated Disaster Information System, which contains data recorded by Civil Defense and local government officials within ten days of an occurrence. 

“We must highlight the importance of having integrated disaster information systems such as the Brazilian S2iD, which provides valuable and timely information that allows us to quantify the impacts of extreme events”, said the researchers.

The study area was subdivided into 12 mesoregions of Minas Gerais (official units forming a set of cities that share geographic and social characteristics), with a total of 194 municipalities. Altogether, the state has 853 cities.

“The most affected mesoregions were the metropolitan area of ​​Belo Horizonte, Vale do Rio Doce and Zona da Mata. Together, they were responsible for 91% of public economic losses and 93% of private economic losses, in addition to 92% of total material damage. In total, 91% of the population was displaced”, says the article.

These areas also exhibited the most alarming numbers regarding the vulnerability to disasters of residents and dwellings in officially mapped risk areas, according to the scientists.

Poor and vulnerable people were most harmed by the floods

They also note that, although the event was extreme and influenced by climate change, its impacts were exacerbated by the lack of urban risk management planning, mitigation and adaptation strategies, as well as underinvestment in infrastructure, which may have disproportionately affected the poor who live in high-risk situations, such as precarious hillside housing.

“We therefore interpret the impacts of this event as a socially constructed climate disaster,” they said, suggesting that future studies should investigate the impact of extreme weather events on poor and vulnerable people. 

“Furthermore, future research may also address the increasingly complicated interactions of human, economic and political aspects within ecological systems,” they add.

According to Dal'Agnol, the model developed to analyze the mining disaster can be applied to other regions. “The methodology can be used to analyze other events. At the time of our study, we found little research on extreme weather events in Brazil. More studies like this one are needed to identify regions that are particularly vulnerable to climate change so that government and public policies can be properly prepared to prevent future disasters”.

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