ppm
About the CO2UNTER
Every month, flasks of air are collected at a worldwide network of stations and sent to the Earth Systems Research Laboratory in the States for analysis. A number of gases are measured, including carbon dioxide. The record of carbon dioxide concentrations available from ESRL now stretches back over 50 years.
The data files of CO2 concentrations that ESRL produce are updated every month as new data comes in from the network of monitoring sites. It is this data that we use to estimate the current global CO2 level.
From the data files, we know that the most recent measurement of global CO2 was taken on the , when the mean concentration at sea level was parts per million. The current concentration is calculated by correcting the last measured value with an increase estimated from the rate of concentration change averaged over the last 5 years (currently an increase of parts per million per day) multiplied by the elapsed time since the last measurement ( days).
Carbon dioxide has a strong seasonal cycle caused by uptake of CO2 by growing vegetation in the spring, and release of CO2 as it decays again in the autumn. On the graph opposite the red line shows measurements by the global network over the last five years. The black line is the same data, but adjusted to remove seasonal fluctations. The current concentration that we report is estimated simply by extending the black line to the present day.
