# Evaluating Uncertainties in Marine Biogeochemical Models: Benchmarking Aerosol Precursors
## 4 Discussion
Marine biogeochemical data providers are therefore encouraged to present the community with observational uncertainties, when available, in addition to raw values. Model skill can be better evaluated when benchmarked against data within the uncertainty bounds of the observation. It is unrealistic to expect system simulations to match specific values acquired on a restricted spatial scale. The complexity of the marine aerosol benchmarking exercise stems partly from the ambiguities in the representation of the underlying global ecosystem within the ESMs. The corresponding atmospheric component of the model plays a strong role as well, and the associated uncertainties may be additive or antagonistic. However, in any case, a constructive effort to disentangle the subtleties begins with an objective benchmarking effort, which is focused specifically on marine biogeochemical processes. In coupled ESMs, over-prediction of the amount of natural sulfate originating from the ocean could create a false impression of increased sulfate aerosols and CCN. The resulting bias will necessarily offset global warming. Model intercomparison exercises show considerable deviation among participating groups. This challenges the reliability of at least some results. In light of this, a standard objective analysis against high quality observational datasets provides an enhanced level of fidelity and reliability. We have performed our demonstrations here on dimethylsulfide distributions for three crucial reasons: (1) its natural aerosol feedbacks have been studied now for decades (CLAW), so that many thousands of insitu (analytical chemical) measurements have accumulated [13; 14]; (2) organosulfur forms a logical starting point for the study of biogeochemical marine aerosol sources taken as a class [2; 79]; and (3) as a methylated compound, DMS acts as a natural bridge to the next generation of modeling problems posed by dissolved organics as a whole. In fact, reduced sulfur processing highlights many of the most basic needs for the benchmarking of marine aerosol systems. Global biogeochemistry validation must soon extend in several new directions, and it is perhaps worth previewing them here at the level of discussion. The DMS database itself continues to modernize. There are now algorithms available for the inversion of remotely sensed light fields to estimate concentration distributions [33]. A certain amount of kinetics is involved, since relationships to the precursor dimethyl sulfonio-propionate (DMSP) are fundamental. The method is sufficiently new, so it may take considerable time to evolve toward fidelity; currently, the results are unpublished. However, it is possible that even the tens of thousands of determinations that have been analyzed by [PERSON] et al. [14] may soon prove to be just a starting point. The bulk of organic carbon released from phytoplankton does not contain sulfur as the major heteroatom [12]. Most of the mass injected into the upper ocean water column is comprised of major components of the cytosol: proteins, polysaccharides, and lipids are most abundant. Some of the functionalities implied are extremely amphiphilic, and thus are surface active. The proteins and lipids must therefore participate directly in sea salt mass injections to the tropospheric boundary layer, with attendant regulatory effects [2; 80; 81]. The latter take place through biomacromolecular adjustments to the distributed global marine surface tension [3; 82]. As important as CLAW would seem to be, it can thus be argued that DMS is in fact merely one player among a host of organochemicals controlling marine particle injections. The major surface-active macromolecules are biopolymeric, and hence they cannot enter the troposphere in the gas phase. However, they necessarily degrade through poorly understood channels into volatile compounds, with isoprene and the monoterenes serving as major examples [83; 26].