# Mauna Loa and South Pole Isotopic ^{13}C Ratio (y-axis inverted)

## Description

The scale of δ^{13}C is inverted so that seasonal patterns of CO_{2} concentration δ^{13}C appear with the same phasing.

Black Dots: Monthly average reduced isotopic ratio of atmospheric carbon dioxide, δ^{13}C, versus time at Mauna Loa Observatory, Hawaii (20°N, 156°W) where δ^{13}C is in per mil.

Black Curve: The sum of 4 seasonal harmonics and a spline function to the Mauna Loa δ^{13}C data. The seasonal harmonics include a linear gain factor, to represent increasing amplitude with time.

Red Dots: Monthly average atmospheric carbon dioxide reduced isotopic ratio, δ^{13}C, versus time at South Pole, Antarctica where δ^{13}C is in per mil.

Red Curve: The sum of 4 seasonal harmonics and a spline function to the South Pole δ^{13}C data. The seasonal harmonics include a linear gain factor, to represent increasing amplitude with time.

Data from Scripps CO_{2} Program.