400 hundred parts per million
The only good news about the Earth’s record greenhouse-gas levels is that they have been well measured.
Charles D. Keeling was a somewhat courtly man who changed the way people and governments see the world.
He built an instrument is 1956 that could measure the proportion of carbon dioxide in the atmosphere, a scientific topic which, back then, was barely even a backwater.
He installed these instruments high up on Mount Loa, a Hawaiian volcano. And found that the carbon dioxide level fluctuated with the seasons, falling in northern summer as plants took up carbon dioxide and rising in northern winter as dead foliage rotted. This resulted in the annual average to be 315 parts per million (ppm)
This rising increase created the “Keeling curve” which became an icon of climate change science.
This curve has now broken the 400ppm barrier for the first time.
The 400ppm barrier has a psychological weight beyond any physiological significance, the mere fact the number is known carries with it an important lesson. To think about how to look after the planet, you need an objective measure of how it has been changing over time.
Useful environmental measurements are made all over the world, but too few are made consistently across the decades; data are taken over a funding cycle, or the life of a satellite and then not again. However, when charting the course of a changing planet, it is consistency that matters.
Scientists involved in other measurements of the Earth and those who pay for their work, need to build on this legacy. A world spending trillions of dollars to change the shape of the Keeling curve but do not find the funds to produce consistent records of the change going on today, is one that still has lessons to learn from the patient chemist, Charles D Keeling.
Source:The Economist May 2013-05-23