The atmospheric transport studies of Keeling et al. (1989) and Tans
et al. (1990) raise important issues about the carbon cycle. They
force us to look at the carbon cycle as a global system, which may
include large terrestrial carbon sinks due to CO
fertilization. Tans et al. have challenged the idea that the ocean
is an important CO
sink. However, research over the last
four years supports the idea that the ocean is probably taking up
2 GtC/yr of anthropogenic CO
. It suggests that this
level of uptake can be reconciled with atmospheric CO
gradients. A complete reconciliation involves a renewed emphasis
on the natural carbon cycle as it pertains to interhemispheric
transport, nutrient cycles, and river fluxes.
The next four years of carbon research will be focused on a better
characterization of the ocean's DIC and 
pCO
fields
and a better characterization of the 
C system,
including atmospheric measurements of 
C, which should
allow use of atmospheric 
C gradients to constrain
aspects of the carbon cycle. We should also expect to see a
renewed emphasis on the natural carbon cycle in ocean general
circulation models (GCMs). Ocean GCMs have not, to this point,
been used to very effectively to study the natural carbon cycle and
its effect on the perturbed modern carbon system.