The Keeling curve

The increase in the concentration of greenhouse gases (GHG) in the atmosphere, normally referred to as carbon dioxide equivalent (CO2 eq), is unequivocally caused by human activity, mainly by the burning of fossil fuels, deforestation and the burning of native vegetation.

It is possible to calculate the emissions arising from these two sectors, as we know how much fossil fuel is consumed each year, and what the rate of conversion into CO2 is, the same occurring with rampant deforestation and the burning of plant material. Not all carbon dioxide emitted goes into the atmosphere, around 57% of emissions actually remain in the air. The remainder is partially absorbed in the oceans and another part is used in photosynthesis, with a portion fixed in biomass for variable periods of time.

A little of history

The study of the relationship between GHG emissions and climate change is almost two centuries old. One of the first studies on the subject was carried out by Eunice Foots, an American scientist. She published in The American Journal of Science and Arts, in 1856, a simple experiment. She filled three glass cups – one with water vapor, another with CO2 and a third with air, observing how they behaved when exposed to the sun. The glass with carbon dioxide heated up much more than the others and took longer to cool down. This study is the basis for demonstrating the greenhouse effect, modulated by the composition of gases and water vapor, in the atmosphere.

At approximately the same time, and without knowing Eunice's work, the Irishman John Tyndall demonstrated how certain gases, including CO2, capture heat in the atmosphere, publishing his studies in 1859. Another pioneer was the Swedish scientist Svante Arrhenius who, in the midst of 2th century, calculated the theoretical impact of an increase in CO2 in the atmosphere. He estimated that doubling the concentration of CO6 in the atmosphere could increase the planet's average temperature by up to XNUMXºC.

Around 70 years ago, an American chemist, Charles Keeling, observed the intense increase in the concentration of CO2 in the atmosphere. As a result of his studies and persistence, US institutions, such as universities and the National Oceanic and Atmospheric Agency (NOAA), began to record carbon dioxide levels in the atmosphere. In honor of the pioneer, this record came to be known as the Keeling Curve. The advance of the curve over time can be checked at address keelingcurve.ucsd.edu.

The gift

NOAA's Mauna Loa Observatory, located on the northern flank of the extinct volcano of the same name in Hawaii, at an altitude of 3.397m above sea level, is the reference point for estimating atmospheric CO2 concentration. The location was chosen because it is far from large urban centers and places with strong GHG emissions, to avoid distortions, and to verify how emissions, although localized, would be distributed in the global atmosphere. The information to establish the Keeling Curve comes from this observatory.

Scientists estimate that the concentration of atmospheric CO2 was once higher than at present, but this occurred many millions of years ago. Because the burning of fossil fuels is unnatural, recent increases in carbon in the atmosphere, oceans, and Earth's biosphere cannot be natural either. What most attracts scientists' attention is not so much the concentration of carbon dioxide – although very high – but the rate of increase, which has nothing to do with the recent past, say, the last 800.000 years. Few natural processes can release fossil carbon into the atmosphere as quickly as we humans are doing now with the extraction and use of fossil fuels, deforestation and burning of native vegetation.

In the 1990s, global society became concerned about global warming. Currently, the climate is monitored by numerous satellites and thousands of thermometers spread across the world. And monitoring is not only carried out for scientific or environmental reasons, the social and economic impact has been shown to be very intense.

In recent years, in the United States, climate change has been identified as responsible for reductions in GDP of around US$1,3 trillion. In 2018 alone, losses were estimated at US$80 billion. Although there are no global studies, it is estimated that this impact reaches trillions of dollars (Learn more).

Proposals to avoid an emerging catastrophe include reducing the use of fossil fuels, eliminating unnecessary burning of native vegetation and reducing the climate footprint of livestock farming.

Meanwhile, the solution faces scientific denialism from those who insist on denying climate change, despite all evidence to the contrary. Furthermore, there are numerous important economic interests at stake, such as the production and use of oil, gas and coal, and illegal logging in the remaining forests. Without a global commitment from all social and economic actors, the price that future generations will pay will be very high, perhaps even impossible to pay.

Décio Luiz Gazzoni, member of the Sustainable Agro Scientific Council