365 Days of Climate Awareness

8 - Measuring Atmospheric Carbon Dioxide

The Mauna Loa observatory is at 3400m elevation in Hawaii, a location chosen for its isolation relative to cities and other large-scale CO₂ sources and sinks, and elevated enough that the atmosphere can be assumed to be globally well-mixed. The Pacific is used also for measuring another important benchmark, eustatic (global) sea level, the topic of a post to come. This record is not the same as the global average, which is calculated from a worldwide set of island-based CO₂ monitoring stations (including Mauna Loa). Island monitoring stations are considered to be the best means of avoiding biases from continental sources and sinks.

The record dates from 1958 and has been called "the backbone of climate change science". It gives not only a clear representation of the growing speed of CO₂ concentration in the atmosphere, but also provides a clear correlation with other data streams such as air and ocean temperature, ice mass (i.e. loss), sea level rise, and more.

Mauna Loa record of atmospheric carbon dioxide concentration.

Modern-day, highly precise measurements can be used to correlate with and statistically constrain methods of estimating prior atmospheric CO₂ concentrations, which is vital to climate change science. A feature of the trend is the almost metronomic annual rise and fall, averaging out to the smoothly increasing trend line. These annual fluctuations are due to seasonal effects on forests and other photosynthesizing regions. This effect is observed worldwide. Over the course of the sixty-plus years in which data has been tabulated, the atmospheric carbon dioxide concentration has increased from 315 ppm to nearly 420, an increase of almost exactly 33%.

Tomorrow: historical (paleo-) CO₂ measurements.

Be well!

Mauna Loa carbon dioxide record