ALT and PTB Stations Isotopic C13 Trends Graphic | Scripps CO2 Program

ALT and PTB Stations Isotopic 13C Trends


Black Dots: Monthly average atmospheric Isotopic C13 concentration versus time at stations in the Northern and Southern Hemispheres where 13C concentration is in parts per million in the mole fraction (p.p.m.).

Black Curves: The sum of 4 seasonal harmonics and a spline function to the stations 13C concentration data. The seasonal harmonics include a linear gain factor, to represent increasing amplitude with time.

Station code names are as follows: ALT = Alert, NWT, Canada, and PTB = Point Barrow.

Data from Scripps CO2 Program.

Data sharing policy

The data and graphics on this website are made freely available, with the understanding that appropriate credit will be given. For applications supporting peer-reviewed scientific publications, coauthorship may sometimes be appropriate. An example would be if an important result or conclusion depends on this product, such as the first account of a previously unreported phenomenon. Ethical usage requires disclosing intentions at early stages of the work in order to avoid duplicating ongoing studies at Scripps. For applications where coauthorship is not needed, which includes all applications outside of the peer-reviewed scientific literature, it is sufficient to acknowledge the Scripps CO2 program as the source. Please direct queries to Ralph Keeling (