Extreme and connected climatic phenomena

Events on one side of the planet can affect those on the other, say scientists. One example is El Niño, which causes drought in the Northeast of Brazil and intense rains in the South, and cause of which may be related to warming of the Indian Ocean.

By Washington Castilhos, in Rio de Janeiro

Agência FAPESP – Teleconnections are remote relationships. Events on one side of the planet can affect what happens on the other side. One example is El Niño, a climatic phenomenon of tropical origin caused by abnormal warming of the waters in the Pacific Ocean. Some of El Niño’s effects are drought in Brazil’s Northeast and heavy rains in the South.

El Niño’s origin provides another example of teleconnection: the cause of the phenomenon—warming of the western Pacific—could be related to higher temperatures of the Indian Ocean.

According to José Marengo, a researcher at the National Institute for Space Research (INPE) Earth System Science Center, identifying teleconnections and analyzing their influences on atmospheric circulation could be useful in understanding abnormal events across the globe.

“Teleconnections are associated with natural causes and not man’s influence. Over a 100-year period, oscillating patterns can be observed that affect the climate of certain regions—like El Niño, the Pacific Decadal Oscillation and the North Atlantic Oscillation. For example, today we are in a phase where the Pacific Ocean is cooler and the Atlantic plays a more active role,” said Marengo, who is a member of the Intergovernmental Panel on Climate Change (IPCC) for the Symposium on the Relationship Between the Oceans and Continents and its Role in Global Change held by the Brazilian Academy of Sciences (ABC) in October.

Recent studies have shown that El Niño has different facets. In analyzing the phenomena occurring between 1900 and 2012, a group led by Edmo Campos, professor at the Universidade de São Paulo Oceanographic Institute (IO-USP), observed 14 drier events and 14 wetter events.

“The explanation for this comes from the South Atlantic, which plays a determining role in whether El Niño will be ‘wet’ or ‘dry’. A series of events influencing the global climate occurs in the Atlantic. El Niño doesn’t depend on the Atlantic, but its impacts will vary depending on the interactions between the Atlantic and the Pacific,” said Campos, who coordinates research projects funded by FAPESP such as “Impact of the Southern Atlantic on the global overturning circulation (MOC) and climate (SAMOC)”.

According to Campos, observations and models show that variations in the Meridional Overturning Cell, or MOC, are strongly related to significant changes in climate. Until now, most observations have focused on the North Atlantic.

“However, studies show that the South Atlantic isn’t merely a passive conductor of water masses formed in other regions and that changes in the return flow of the MOC in the South Atlantic could significantly impact the regional and global climate,” Campos told Agência FAPESP.

“So, a weak MOC results in a warmer South Atlantic, which can mean more rain in the Brazilian Northeast. El Niño has assumed a more passive role, while the Atlantic Ocean today has a more active one,” he pointed out.

Extreme events

Björn Kjerfve, the president of Sweden’s World Maritime University (WMU), stresses that the oceans play a predominant role in any climate change scenario. “The oceans are regulators of the planet’s climate. If Earth’s average temperature rises by one degree, a certain amount of ice will melt,” Kjerfve said at the symposium.

Warming of the South Atlantic resulted in the Catarina cyclone, which struck southern Brazil in March 2004. A warmer North Atlantic caused Hurricane Sandy, which recently hit the East Coast of the United States. “Cyclones are closely related to the temperature of the sea. They only happen if the ocean’s surface is warmer than 26 degrees. Catarina happened because, for some reason, the water temperature was higher than average,” said Campos.

As the tendency toward warmer waters in the South Atlantic persists, Brazil could be hit by more cyclones. “The average amount of rain has increased on the global level along with a rise in the planet’s temperature, but we don’t know if this will create favorable conditions for these events,” said Campos, stressing that the IPCC reports do not offer a definitive answer as to the occurrence of extreme events such as cyclones.

The warmer-than-normal winter and cool beginning of springtime in Brazil in 2012 could indicate a natural adjustment. “We are at the end of a dry period. This dry period is due to global warming, which has both natural and anthropic causes. Human beings intensify warming. However, we can’t attribute these anomalies exclusively to human activity,” said Campos, who coordinates the PIRATA Project, a cooperative program among Brazil, France and the United States created in 1995 that monitors the Atlantic Ocean.

“We know much more about the Pacific than the Atlantic. The most significant connection between the ocean and our coast is the tropical region, which is why it’s important to monitor the region where it bifurcates with the South Equatorial Current. The pre-salt layer, for example, will be affected by phenomena occurring very far away,” said the IO-USP professor.

“We still haven’t come very far in terms of oceanography. But Brazil will be the first nation to be directly affected by changes in the South Atlantic. We are closely connected with the Atlantic Ocean. That’s why Brazil must be at the forefront of studies on the South Atlantic,” said Campos.