by Robert H. Socolow | Princeton University

In 1958, Charles David Keeling began measuring the concentration of carbon dioxide (CO2) in the atmosphere, at a site 11,000 feet above sea level near the top of Mauna Loa on the “big island” of Hawaii.
The time series of monthly averages, the “Keeling Curve,” is the iconic figure of climate change. The curve oscillates and rises. The annual oscillations are the consequences of the seasonal breathing of the northern-hemisphere forests, which remove CO2 from the atmosphere during their growing season and return CO2 to the atmosphere as their leaves decay on the forest floor in winter. The steady rise – on average today, about 0.5 per cent per year – is due primarily to the burning of fossil fuels. Indeed, the average rise would be twice as fast if all of the CO2 released during fossil-fuel burning stayed in the atmosphere. Roughly half of the CO2 emissions from burning fossil fuels stay in the atmosphere, one quarter go into the ocean (making it more acidic), and one quarter enter forests that, despite deforestation, are growing bigger.


The era of consciousness of climate change began with Keeling’s intrepid measurements. The seasonal oscillations were unexpected, and it was soon clear that atmospheric CO2 measurements were a new index of global human impact. The political message was that the global atmosphere mixes and retains a large part of the world’s CO2 emissions, oblivious to what fuel is burned, in what country, and for what purpose. Again and again over the past fifty years, modellers have estimated future human emissions on the basis of assumptions about the economy and technology, while environmental scientists have gradually improved their ability to describe the likely consequences for global warming, sea-level rise, ecosystem disturbance, and hydrocycle disruption (storms, floods, droughts, etcetera).


The landmark international treaty, the United Nations Framework Convention on Climate Change (“UNFCCC”), is often called the Rio Convention, because it was negotiated in Rio de Janeiro at the “Earth Summit” in June of 1992. The rate of fossil fuel emissions almost tripled between 1958 and 1992 (from 8.5 to 22.7 billion tons of CO2 per year, an average increase of 2.9 per centper year for thirty-four years).
By 2010, it had increased by another 40 per cent (to 33.5 billion tons of CO2 per year, an average increase of 2.2 per cent per year for eighteen years) and was four times larger than in 1958. In my view, the environmental community does not need to wait for economic recovery or political reform or the withering away of disinformation campaigns to tackle the climate change challenge. We will find “restart buttons” when we become better at telling truths to ourselves. [...]

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