Chat:
Rosa Compagnucci, is Leading Researcher at CONICET, professor in the Department of Atmosphere Sciences in the University of Buenos Aires, Member of the IPCC Working Group II for the Chapter on Latin America, and specialist on the "El Niño" phenomenon.
Alejandra Salles is Doctor of Atmosphere Sciences
Martín: Dr. Salles, what is your speciality?
Alejandra-Salles: I am a Dr. in Atmosphere Sciences and my thesis was on atmospheric circulation in southern South America and its relation with anomalies in temperature and precipitation. Within this study, I analysed the impact of ENSO on atmospheric circulation.
b What is ENSO?Alejandra-Salles: The term ENSO (El Niño/Southern Oscillation) is used to describe the simultaneous occurrence of an ocean phenomenon known as el Niño and another atmospheric one known as the Southern Oscillation. The ocean phenomenon, el Niño, has been known of since the era of the Spanish Conquest and consists of a weakening of the surges of sub-superficial waters of the Pacific Ocean along the coasts of Peru and Ecuador.
Martín: Dr. where does la Niña come from?
Alejandra-Salles: La Niña is the opposite event to el Niño. That is, a cooling of the superficial level of the sea along the coasts of Peru and Ecuador associated with a positive Southern Oscillation.
Dana: Do you believe climate changes are gradual?
Rosa-Compagnucci: What do you call abrupt or gradual? Geologists class 10,000 years as abrupt and meteorologists, one year. We came out of the last Ice Age 18,000 years ago and in a thousand years the land temperature increased by an average of 10 degrees.
Dana: Abrupt… maybe a limited time, like a year?
Rosa-Compagnucci: El Niño produces reversible changes in intervals of a year, zones which were dry, like the coast of Peru, can have see precipitation and then return to being dry.
Dana: And do the el Niño and la Niña only happen in the Americas? Or is there something similar in Europe? I mean, rather, the eastern sector of the planet?
Rosa-Compagnucci: Both el Niño and la Niña are ocean phenomena of the Equatorial Pacific Ocean but their impact is global, hence they also affect Europe.
Dana: And why is this happening?
Rosa-Compagnucci: Because this area was covered by an ice cap 5,000 metres thick which started to melt 18,000 years ago and suddenly the water from this massive lake broke through a natural barrier and spilled into the sea.
In the mini Ice Age from the 17th to 19th centuries, el Niño events were more frequent and more intense.
b Yesterday I heard IPCC members say tangible climate changes could take place in a minimum period of 50 years.
Rosa-Compagnucci: Yes, it's possible. The Younger Drys were unleashed between 10,000 and 50,000 years ago, but a natural catastrophe contributed to this - a great lake of cold water, which covered the north of the United States and the east of Canada, suddenly spilled into the North Atlantic.
Martín: Are changes evident in the occurrence of strange meteorological phenomena (hurricanes, tornadoes, etc.) since the end of the industrial revolution?
Rosa-Compagnucci: Yes.
Martín: Is the difference very big?
Rosa-Compagnucci: The inter-year variability is great, for example: in 1997 -winter in the southern hemisphere, summer in the north, the el Niño phenomenon - there were many hurricanes along the coast of Japan and in the Western Pacific. And in the winter of 1998 in the southern hemisphere, summer in the northern hemisphere, many hurricanes in the Caribbean and few on the other side.
Martín: Have advances been made in studying the origin of both tornadoes and hurricanes?
Rosa-Compagnucci: Yes, tornadoes in Argentina are due to very high summer temperatures, and above all to high humidity in the atmosphere and a surface wind flow from the north, a high altitude wind flow from the west and, if the dew-point temperature exceeds 24 degrees, we are in danger of having a tornado. Hurricanes take place in zones where the sea temperature exceeds 24 degrees centigrade and it moves to zones of the same, or a higher temperature, hence its route can be predicted with some security.
Martín: Tornadoes in Argentina? Are they usually very big?Alejandra-Salles: There are tornadoes in Argentina, and over the city of Buenos Aires too.
Rosa-Compagnucci: Yes, in the north-east of Argentina tornadoes are very frequent and tend to be of great strength, but not as much as those registered in zones of the United States. But they cause a great deal of damage.
Dana: In Buenos Aires?
Rosa-Compagnucci: Yes, there was a tornado in Mar del Plata last year.
Alejandra-Salles: Yes, and there were two which could be seen over the River Plate only a few years ago.
Martín: What is the difference between climate and weather? (I need to know because I'll be studying Agricultural Climatology next year.)
b Weather is what takes place in the short term, instantaneously, climate gives you the more general conditions.
b But the forecasts are often wrong?
Rosa-Compagnucci: I can say if it's going to be colder or hotter, if it is going to rain more or less, but I don't have any idea what a society might do with that. That must be decided by the government, industrialists, farmers and society in general
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