What was done
The authors review the progress we have made over the past two decades in attempting to better understand the global carbon cycle.

What was learned
The authors begin by noting that the scientific establishment's early views on this subject - as expressed by the first leader of the Intergovernmental Panel on Climate Change - have had to be drastically revised.  In their own words, "early estimates of huge losses of carbon from plants and soils due to biomass burning and deforestation have recently given way to the idea of a terrestrial biosphere nearly balanced (globally) with respect to carbon."  What brought about this change in thinking?  It was forced, as they accurately report, by data, and lots of it.

First on the authors' "show me the science" list (see Editorial Commentary -- Volume 1, Number 2) is the fact that ocean models constrained by ¹⁴C, tritium and chlorofluorocarbon data do not easily allow for the high terrestrial CO2 emissions that were originally postulated.  Second, the smaller-than-expected, i.e., the actually observed as opposed to the merely "expected," north-south gradient of atmospheric CO2, when combined with real-world data on the partial pressure of CO2 in the surface waters of the world's oceans, suggests that "there has to be" a large terrestrial sink for CO2 at temperate northern latitudes.  Third, measurements of the atmosphere's oxygen/nitrogen ratio clearly reveal the effects of fossil fuel burning; but deforestation, which also involves burning, provides barely a hint of its existence in the data.  Fourth, ¹³C/¹²C measurements of atmospheric CO2 also reveal the existence of a large terrestrial sink for CO2 at temperate northern latitudes.  Fifth, measurements of the vertical transport of CO2 over forest ecosystems conducted in a number of different places over the last several years all tend to show that forests are substantial sinks for CO2.  Sixth, the increasing amplitude of the atmosphere's seasonal CO2 cycle is consistent with the (increasing) uptake of CO2 by temperate land ecosystems.  Seventh, ditto for the increasingly earlier onset of the summer photosynthetic drawdown portion of this cycle.  Eighth, worldwide forest surveys, especially those of recent decades, generally reveal a significant net sequestration of carbon.

What it means
Data obtained over the past two decades in several different and independent areas of research clearly demonstrate that the world's terrestrial ecosystems yearly sequester far more carbon than almost everyone believed possible only a few years ago.  The philosophical take-home message of this revelation is to never blindly accept the predictions of anyone -- even "experts," as it were -- that are not thoroughly founded in factual observations.  Always insist that they "show you the science," i.e., that they present the data upon which their reasoning is based and that they describe the logic by which they extrapolate therefrom.

With respect to the specific subject of earth's carbon cycle, the message of the science is that terrestrial vegetation can exert a much bigger "biospheric brake" on the rate of rise of the air's CO2 content than nearly everyone previously imagined.  But is it big enough to save us from the catastrophic CO2-induced warming predicted by many of the same people who guessed wrong on the sequestration of carbon by terrestrial plants?  One of our Scientific Advisory Board members clearly believes that it is, as he plainly spelled out in 1991 in a pair of publications in the Bulletin of the American Meteorological Society (Vol. 72, pp. 962-965, and pp. 1910-1914).  But is he right?  Only time, and a lot more good hard science, will tell for sure.