There are now 51 years of direct high accuracy observations of CO2 at the Mauna Loa Observatory in Hawaii.  The residuals after removal of the long-term trend and the average seasonal cycle we call anomalies.  They are not random and possess significant serial correlation.  The anomalies are quite similar to a record of global average CO2 during the period of overlap from 1980 until today.  They are thus representative of global CO2.  These anomalies are clearly driven by the response of terrestrial ecosystems to annual climate variations.  We will try to quantify these year-to-year variations, in order to better detect underlying decadal-scale trends that could be important for long-term projections of climate.

Results/Conclusions

Purely statistical lagged response functions, without any assumptions about potential mechanisms, are derived to anomalies of global temperature and precipitation.  For temperature, the response is initially positive (CO2 released to the atmosphere), but changes sign a year later.  For precipitation, the response is negative, and gradually declining over the course of a year.  Together, these two response functions explain two-thirds of the observed interannual variation of the CO2 anomalies.  After correcting the CO2 record for the above short-term response it becomes very clear that the rate of atmospheric CO2 growth has accelerated, and that there are significant unexplained decadal variations.