Diplomats just finished a marathon round of climate talks in Lima, Peru, which resulted in an agreement that for the first time ever will commit each country to taking action to reduce their emissions of global warming pollutants, such as carbon dioxide. The agreement leaves much still to be decided next year, with a looming deadline for a new climate treaty that will go into effect in 2020.
What negotiators have been trying to do for much of the past two-plus decades is to address the accelerating increase in the amount of carbon dioxide in the planet's atmosphere. Carbon dioxide is released when burning coal and other fossil fuels for energy, and it lasts hundreds to a thousand years once it is in the air, making a failure to cut emissions now a problem for future generations.
The definitive chart for increasing carbon dioxide concentrations is known as the Keeling Curve. This data began to be collected in 1958 by Charles David Keeling, a scientist at the Scripps Institution of Oceanography. He installed a monitoring device at the summit of Hawaii's Mauna Loa volcano, where the air is relatively free of other air pollution. These measurements are still carried out at Mauna Loa today, led by Keeling's son, Ralph Keeling. Other monitoring devices are also deployed worldwide to collect similar data.
In the first part of the 20th century, scientists suspected that carbon dioxide might be increasing because of fossil fuel burning, but few monitoring stations were tracking it. Keeling's readings were the first to raise the alarm that, in fact, carbon dioxide concentrations were rising rapidly, with a seasonal variation as the planet takes in more carbon dioxide during the summer in the Northern Hemisphere, and releases it during the winter as trees lose their leaves.
In other words, the Keeling Curve shows the planet breathing during the course of the year.
Scientists have established through a plethora of studies that show how carbon dioxide levels are tied to global average temperature changes, with the two marching in near (but not exact) lockstep throughout Earth's history. Data going back 800,000 years shows that carbon dioxide levels today are the highest in all of human history, and rising.
According to Scripps, during ice ages, carbon dioxide levels tended to average around 200 parts per million (ppm), and during the comparatively warm interglacial periods, they were higher, at about 280 ppm.
Yet today, the concentration is hovering close to 400 ppm, on their way to at least 450 ppm. The higher carbon dioxide and other greenhouse gas concentrations go, scientists say, the higher global average temperatures will become.
The climate talks in Lima were meant to stop global warming from exceeding the agreed upon temperature target of 2 degrees Celsius, or 3.6 degrees Fahrenheit, above preindustrial levels, beyond which many scientists say dangerous climate impacts, such as the complete melting of the Greenland ice sheet, would occur.
However, given recent emissions trends and the pace of the climate talks, it is quite possible that this temperature target will be at least temporarily exceeded.