Long-term measurements of the characteristics of carbon dioxide lead to fresh knowledge for climate research

The accurate measurement of the ratios of oxygen isotopes in atmospheric carbon dioxide for well over three decades has led to unexpected new information being uncovered about the global Gross Primary Production (GPP) of plants. The GPP has always been difficult to determine, although it is of great importance to research into how climate change is developing. An international group of scientists, including Prof. Harro Meijer of the Center for Isotope Research at the University of Groningen, published these findings in the journal Nature today.

The GPP is the total amount of carbon dioxide (CO2) that green plants take from the atmosphere and turn into organic material through photosynthesis. The ratios of oxygen isotopes in CO2 collected globally show that the El Niño climate pattern can be indirectly used to establish the GPP.

El Niño’s influence can be indirectly gleaned from the ratio of oxygen isotopes in carbon dioxide in the atmosphere. Using data collected since 1977, the effect of El Niño can be used to determine the GPP across the globe. The first series of measurements from 1977 to 1993 was conducted by the Center for Isotope Research on the initiative of its director at the time, Prof. W.G. Mook.

Climate pattern

EL Niño, known in full as El Niño/La Niña-Southern Oscillation (ENSO), is a naturally occurring climate pattern. Every five to seven years it causes a marked change in temperature and rainfall in tropical regions on both sides of the Pacific Ocean. A change in rainfall leads to changes in the ratio of oxygen isotopes in rainwater and subsequently – via contact with the water in the plants during photosynthesis – to the ratio in atmospheric CO2. The degree of change is directly related to the GPP. The collected data clearly show the development of a large number of El Niños in the past thirty years. This in turn makes a reliable determination of the GPP possible.

For more information: Prof. Harro A.J. Meijer

See also: Centre for Isotope Research

Reference:
Interannual variability in the oxygen isotopes of atmospheric CO2 driven by El Niño
DOI: 10.1038/nature10421
Lisa R. Welp, Ralph F. Keeling, Harro A. J. Meijer, Alane F. Bollenbacher, Stephen C. Piper, Kei Yoshimura, Roger J. Francey, Colin E. Allison, and Martin Wahlen
Nature, 29 september 2011