It's a chart of the level of carbon dioxide in the atmosphere and its data has been collected, continuously, from an observatory on Mouna Loa, Hawaii.
From the Keeling Curve website:
The idea of making measurements at Mauna Loa arose while Charles David Keeling was a post-doc at Cal Tech. In the course of working on a project involving carbon in river water - a project that incidentally required making measurements of CO2 in air - Charles David Keeling made a key discovery. What he discovered was that when he sampled the air remote from forests, cities, and other obvious sources or sinks for CO2, he always got almost the same value of 310 ppm.Please note the number. Also note that he got (roughly) the same number wherever he sampled.
He soon discovered a seasonal fluctuation in the level of carbon in the atmosphere.
And then, over the years, he discovered this:
The jagged line shows the seasonal fluctuations. The upward sweep is the overall tendency of those fluctuations - upward.
And what's the importance of carbon dioxide in the atmosphere?
In the 1860s, physicist John Tyndall recognized the Earth's natural greenhouse effect and suggested that slight changes in the atmospheric composition could bring about climatic variations. In 1896, a seminal paper by Swedish scientist Svante Arrhenius first speculated that changes in the levels of carbon dioxide in the atmosphere could substantially alter the surface temperature through the greenhouse effect.And so why am I writing this now?
Charles David Keeling passed away a few years ago. His son Ralph has continued the research and a few days ago he wrote:
We are now approaching the annual low point in the Mauna Loa CO2 curve, which typically happens around the last week of September but varies slightly from year to year. Recent daily and weekly values have remained above 400 parts per million. From this it’s already clear that the monthly value for September will be above 400 ppm, probably around 401 ppm. September is typically but not always the lowest month of the year.And:
The low point reflects the transition between summer and fall, when the uptake of CO2 by vegetation weakens and is overtaken by the release of CO2 from soils.
Is it possible that October 2016 will yield a lower monthly value than September and dip below 400 ppm? Almost impossible.
Concentrations will probably hover around 401 ppm over the next month as we sit near the annual low point. Brief excursions towards lower values are still possible but it already seems safe to conclude that we won’t be seeing a monthly value below 400 ppm this year – or ever again for the indefinite future.When he started, Charles David Keeling found 310ppm everywhere. Now it's 400ppm and rising.
Yah-noe, we could take our cues from the current Presidential campaign and the Republican candidate who says that it's an invention created by and for the Chinese in order to make US manufacturing non-competitive or from the Pennsylvania Senatorial race and the Republican candidate who says that while climate science is not a hoax, human activity is still not a significant factor in the rise of global temperatures.
We could take our cues from them but if we did, we'd be either a mostly (yet still embarrassingly) wrong with the Republican Toomey or yugely (and quite laughingly wrong) with the Republican Trump.
Or we could just go with the science - and the Democratic candidates, Katie McGinty and Hillary Clinton.
Yea, we should probably just go with the science.