Is the Brazilian flooding catastrophe evidence of another global warming era extreme ?

Guest post by Alexandre Aguiar, METSUL Communications Director, Brazil

(note there’s much more here at METSUL’s blog)

Corpses are still under tons of rocks and mud in the hills of Rio de Janeiro, but some experts are already rushing to the microphones here in Brazil and abroad to declare the worst natural disaster in the Brazilian history as a clear and unequivocal evidence of global warming (a.k.a. global climate disruption).

The Brazilian media is not immune to the frenzy on global warming and extreme weather events. The Folha de Sao Paulo newspaper, one of the most important media outlets in the country, published a report connecting the Rio de Janeiro disaster to the Queensland flooding in Australia and the recent snowstorms in the United States and Western Europe.

To establish the ongoing catastrophe in Brazil as a global warming product is a bogus claim in the view of the staff of MetSul Meteorologia. The same can be said to the events of cold snaps and snow in the Northern Hemisphere – strong negative Arctic Oscillation related – and the massive flooding in Australia, a direct result of the strong and natural derived La Niña event.

Rio de Janeiro is subject to heavy or extreme rainfall every year, but this time the amount of precipitation was very heavy and in a short period of time, creating an inland tsunami-like torrent. The risk of major extreme rain episodes this summer was widely anticipated by MetSul meteorologists as analog years strongly pointed to a summer similar to the ones with disastrous events in the past. Rain gauges in Nova Friburgo measured 300 millimeters (12 inches) of rain in just 24 hours from January 11th to 12th. The tragedy happened in the Sierras of Rio de Janeiro (Região Serrana) where major topographical forcing is usually present in extreme rainfall. Moisture flow from the ocean (SSTs are above average in the South Atlantic) find a natural physical barrier in the mountains of Rio de Janeiro, making the region prone to extreme rainfall during summer months and early autumn.

The most affected cities (Petrópolis, Teresópolis and Nova Fribrugo) are located between mountains as high as 5 to 6 thousand feet and besides rivers cross these towns. The only way the water can take are the valleys and the regional rivers. Due to the regional terrain, the major menace to the population is landslide. For many decades Brazilian authorities allowed construction of homes and buildings in the slopes, so every single year landslides with numerous deaths are recorded in the states of Rio de Janeiro, Sao Paulo and Minas Gerais.

The front page of the Extra newspaper from Rio de Janeiro (click over the picture for a wider view) published on January 13th 2010 showed that every single year in the last decade witnessed tragedies caused by rain in the state of Rio. The newspaper headline is “Até quando?” (When will it end?). The paper argues: “The government excuse is always the same…it rained an equivalent to…”. The dominant opinion in the Brazilian media and public arena is that these repeated tragedies must be above all attributed to poor risk management and ridiculous urban planning instead of only blaming nature. Despite recognizing the ferocity of the rain, many are calling this week tragedy a manmade disaster.

In the state of Rio de Janeiro, there is massive occupation of the slopes and the hills, so landslides tend to be much more devastating and tragedies much more frequent. If this week’s rainfall have happened in the same region 35 years ago, the consequences would have been incredibly less dramatic. Satellite pictures released by the Brazilian Global TV Network show clearly some of the risky areas that concentrate most of the victims (Caleme, Posse and Meudon) as heavily populated nowadays in contrast to low or no land occupation 35 years ago.

There are anecdotal and historic accounts of extreme rainfall in the state of Rio de Janeiro since Brazil was a Portuguese colony in the 1600’s and 1700’s, but meteorological records are not available for that period. Great tragedies caused by rain and landslides in Rio de Janeiro began mainly in the second half of the 20th century coinciding with the demographic explosion and the massive and unorganized occupation of the hills. The risky areas of today, where the tragedies of the modern times use to happen almost every year, were not occupied 100 years ago, and for that reason the vast majority of the tragic events concentrate in the last 50 years.

• April 1756 – Three days of heavy rainfall caused flooding, home collapses and “lots of victims” all over the town – still small – of Rio de Janeiro.
• February 1811 – Between February 10th and 17th heavy rains caused a “catastrophe” in the city of Rio de Janeiro. Hills collapsed, the city was flooded and landslides were widespread with a torrent of water and mud invading town. Historical accounts tell of many victims, but there is no official number. The regent prince – designated by Portugal – ordered the churches to be open to serve as shelters.

• April 1883 – Eleven inches of rain (220 mm) in a matter of four hours flood the city of Rio de Janeiro.

• April 1924 – Heavy flooding and landslides with fatalities.
• January 1940 – Flooding and landslides in the city of Rio de Janeiro. Santo Cristo district was the most affected.

• January 1942 – Flooding and landslides in the city of Rio de Janeiro. The Salgueiro Hill was the the main disaster area.

• January 1962 – Heavy flooding and several landslides in the city of Rio de Janeiro after 242 mm of precipitation during a storm.
• January 1966 – The storm of January 2nd, 1966, brought record rainfall to the city of Rio de Janeiro. Flooding and massive landslides caused 250 casualties. Other 70 people died after the storm due to diseases.

• January 1967 – Heavy rain and landslides provoked the collapses of buildings in the city of Rio. 200 people died and 300 were injured. 300 people died in the states of Rio de Janeiro and Guanabara (today Guanabara and Rio form the state of Rio de Janeiro).

• November 1981 – Landslides in the Sierras of Rio kill 20 people in the city of Teresopolis.
• February 1987 – Flooding and landslides kill 292 people. The city of Rio de Janeiro and the Sierras of the state concentrate the damages and the victims.
• February 1988 – 277 people died in flooding and landslides in the Baixada Fluminense region and in the city of Petrópolis in the Sierras. In the rest of the month hundreds more died in new landslides and flooding. A hospital collapsed, killing 18 people. Damages topped 1 billion dollars.

• Summer of 1996 – Dozens of deaths in flooding and landslides.
• January 1999 – Dozens of deaths in flooding and landslides.
• 2010 – Nearly 100 people died in the cities of Angra dos Reis and Rio de Janeiro due to landslides on January 1st. In April, record rainfall caused over 200 deaths in massive landslides in the cities of Rio and the neighboring town of Niteroi.

Tragic events will happen again in the future, but can be less dramatic if some steps are taken urgently and seriously: improvement of risk management, urban reorganizing, investments in weather forecast and monitoring equipments and staff, a new media approach to weather warnings’ importance and a good public governance. History proves these areas will be hit again, but we as society have the power to mitigate the consequences. It is a matter of serious and urgent public priority for our authorities and the population’s will.

Author: Alexandre Amaral de Aguiar