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50 years ago

Notes and recollections

 from Mexico City

Emilsson in 1957

In 1957, a conference was held in Rio de Janeiro in preparation for a global event called the International Geophysical Year. This conference was attended by North American and Latin American scientists: Argentineans, Brazilians, Chileans, Peruvians and perhaps from  other countries in the region as well. A subject that was very up to date  at the time was the launch, by the USA, of a geophysical satellite, in charge of the California Jet Propulsion Laboratory (JPL).

The cooperative plans included establishing a network of observatories to monitor, with binoculars and telescopes, the geophysical satellite that the Americans planned to launch. As the JPL director, Dr. Pickering, told us, “we would like to have visual reports about the satellite in operation, in order to track its orbit.” Today, thanks to  great progress over the last 50 years, director Pickering’s words sound unbelievable. Obviously, it was all in vain: the US satellite did not get off the ground, a moral defeat for the USA. The first one to make it up there was the Soviet Union’s famous Sputnik.

One of the many subjects discussed at the conference was the increase of CO2 in the atmosphere, caused by the increased burning of fossil hydrocarbons. In this field, the University of São Paulo’s Oceanographic Institute, Physical Oceanography Section, under my supervision, undertook to quantify  CO2 in the uncontaminated environment of the Brazilian coast. To this end, we compiled air samples at the Cananéia station; these were collected every month and analyzed in our São Paulo laboratory.

A funny note from back then: the amount of tritium in the atmosphere had increased due to the explosion of hydrogen bombs. To track this increase, rain water was collected in Cananéia and a 10-liter sample was regularly sent to Sweden for analysis. In order to export this material, customs demanded an official permit. One of the São Paulo newspapers published a note: “Brazil is already exporting rain water.”

As I mentioned, the increase of CO2 in the atmosphere and its effect on climate were discussed at the Rio conference. The atmosphere is partially transparent to solar radiation. Therefore, a lot of the solar energy that reaches the top of the atmosphere reaches the ground. The percentage of solar energy received at the top of the atmosphere that is reflected back into space is called atmospheric albedo (some 30% of the solar energy is returned to space by this process). The solar radiation that reaches the surface of the Earth is absorbed and warms it up.

One of the basic laws of physics states that a body’s radiant energy is proportional to its absolute temperature to the power of four. Thus, the Earth’s surface, warmed by the Sun, emits radiation upward, in the form of a long wave (heat). This energy emitted by the surface is absorbed by greenhouse gases in the atmosphere (mainly CO2 and water vapor). As the concentration of CO2 increases, the amount of energy absorbed by the atmosphere also increases and, therefore, so does the air temperature. With warmer air, more energy in the form of long waves is emitted by the atmosphere into space (in proportion to the absolute temperature of the atmosphere to the power of four). Thus, the Earth’s climate system is balanced at a warmer level when the concentration of CO2 rises.

The production of greenhouse gases due to the burning of fuel and other anthropogenic effects is easily estimated. On the other hand, the distribution of this gas in the Earth’s environment is very complex, and its absorption and transformation are yet to be properly understood. The fact of the matter is that the increase in the atmosphere does not correspond to the calculations that are based on human activities, which means that a substantial portion of this production is absorbed in the Earth’s environment and in the ocean, among other places, generating the so-called  carbon cycle in the sea, which encompasses physical, chemical and biological factors, as well as the circulation of ocean currents, both horizontal and vertical.

The melting of glaciers was among the climatic effects that were foreseen at that time, with a consequent rise in the sea level. In the 1957 discussion, someone mentioned that  docks in the port of New York would be submerged under 12 meters of water. A reporter asked us whether we knew of other ports that would face the same fate. We responded with another question: were there any ports 12 meters above sea level?

It is a well known fact that throughout its history our planet has undergone major climate changes, to which humankind undoubtedly owes its existence. Despite all the research, the origin of these changes is yet to be clearly understood. Not even the last ice age, which finished about ten thousand years ago, is properly understood, even though it has left vestiges that are now disappearing as a result of natural or artificial causes.

Today, just as scientists foresaw more than half a century ago, there is no doubt that the global warming we are currently witnessing is due, to some extent, to anthropic effects. However, the main target now is to distinguish between this effect and the natural fluctuation that has existed throughout our planet’s history.