Correlation of earth temperature and global mean CO2

For teaching purposes I need the CO2 concentration vs earth temperature by year (Keeling curve). For that purpose we can use the Hadcrut 4 dataset created earlier while the global mean CO2 mix ratios (ppm) can be found at
After unscrambling that file and merging it to Hadcrut4 we can plot it

p1 <- ggplot(temp, aes(x=year, y=annual)) + geom_point() + stat_smooth(method="loess", span = .6) +
  scale_y_continuous( name="difference from baseline  [ oC ]", limits=c(-1,1) )

p2 <- ggplot(temp, aes(x=year, y=ppm )) +  geom_point() + stat_smooth(method="loess", span = .6) +
  scale_y_continuous( name=expression('ppm CO'[2]) )

Here are the two time courses

Time course of earth temperature (1850-2018) and CO2 (1850-2011)

while the correlation is higher than I expected

Correlation of earth temperature and CO2



  • 1850-1957: D.M. Etheridge, L.P. Steele, R.L. Langenfelds, R.J. Francey, J.-M. Barnola and V.I. Morgan, 1996, J. Geophys. Res., 101, 4115-4128,”Natural and anthroupogenic changes in atmospheric CO2 over the last 1000 years from air in Antarctic ice and firn”.
  • 1958-1974: Means of Scripps Institution of Oceanography Continuous Data at Mauna Loa and South Pole provided by KenMaarie (personal communication)
  • 1975-1982: Means of NOAA/CMDL in-situ data at Mauna Loa and South Pole. (P. Tans and K.W. Thoning,
  • 1983-2003: Global means constructed using about 70 CMDL CCGG Sampling Network station data. (P.P. Tans and T.J. Conway,
  • 2004-2007: Global mean growth rates. (T. Conway,