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On average, about 45 per cent of global annual anthropogenic carbon dioxide (CO2) emissions remain in the atmosphere, while the remainder are taken up by carbon reservoirs on land and in the oceans—the CO2 ‘sinks’. As sink size and dynamics are highly variable in space and time, cross-verification of reported anthropogenic CO2 emissions with atmospheric CO2 measurements is challenging. Highly variable CO2 sinks also limit the capability to detect anomolous changes in natural carbon reservoirs. This paper argues that significant uncertainty reduction in annual estimates of the global carbon balance could be achieved rapidly through coordinated up-scaling of existing methods, and that this uncertainty reduction would provide incentive for accurate reporting of CO2 emissions at the country level. We estimate that if 5 per cent of global CO2 emissions go unreported and undetected, the associated marginal economic impacts could reach approximately US$20 billion each year by 2050. The net present day value of these impacts aggregated until 2200, and discounted back to the present would have a mean value exceeding US$10 trillion. The costs of potential impacts of unreported emissions far outweigh the costs of enhancement of measurement infrastructure to reduce uncertainty in the global carbon balance.

About one quarter of the CO2 emitted to the atmosphere by human activities is absorbed annually by the ocean. All the processes that influence the oceanic uptake of CO2 are controlled by climate. Hence changes in climate (both natural and human-induced) are expected to alter the uptake of CO2 by the ocean. However, available information that constrains the direction, magnitude, or rapidity of the response of ocean CO2 to changes in climate is limited. We present an analysis of oceanic CO2 trends for 1981 to 2007 from data and a model. Our analysis suggests that the global ocean responded to recent changes in climate by outgassing some preindustrial carbon, in part compensating the oceanic uptake of anthropogenic CO2. Using a model, we estimate that climate change and variability reduced the CO2 uptake by 12% compared to a simulation where constant climate is imposed, and offset 63% of the trend in response to increasing atmospheric CO2 alone. The response is caused by changes in wind patterns and ocean warming, with important nonlinear effects that amplify the response of oceanic CO2 to changes in climate by > 30%.

There has never been a greater need for delivering timely and policy-relevant information on the magnitude and evolution of the human-disturbed carbon cycle. In this paper, we present the main thematic areas of an ongoing global research agenda and prioritize future needs based on relevance for the evolution of the carbon climate human system. These include firstly, the delivery of routine updates of global and regional carbon budgets, including its attribution of variability and trends to underlying drivers; secondly, the assessment of the magnitude of the carbon climate feedback; and thirdly, the exploration of pathways to climate stabilization and their uncertainties. Underpinning much of this research is the optimal deployment of a global carbon monitoring system that includes biophysical and socio-economic components.

Emissions of CO2 are the main contributor to anthropogenic climate change. Here we present updated information on their present and near-future estimates. We calculate that global CO2 emissions from fossil fuel burning decreased by 1.3% in 2009 owing to the global financial and economic crisis that started in 2008; this is half the decrease anticipated a year ago1. If economic growth proceeds as expected2, emissions are projected to increase by more than 3% in 2010, approaching the high emissions growth rates that were observed from 2000 to 20081, 3, 4. We estimate that recent CO2 emissions from deforestation and other land-use changes (LUCs) have declined compared with the 1990s, primarily because of reduced rates of deforestation in the tropics5 and a smaller contribution owing to forest regrowth elsewhere.

[1] Microzooplankton ingest a significant fraction of primary production in the ocean and thus remineralize nutrients and stimulate regenerated primary production. We synthesized observations on microzooplankton carbon-specific grazing rate, partitioning of grazed material, respiration rate, microzooplankton biomass, microzooplankton-mediated phytoplankton mortality rate, and phytoplankton growth rate. We used these observations to parameterize and evaluate the microzooplankton compartment in a global biogeochemical model that represents five plankton functional types. Microzooplankton biomasses predicted in this simulation are closer to the independently derived evaluation data than in the previous model version. Most rates, including primary production, microzooplankton grazing, and export of sinking detritus are within observational constraints. However, the model underestimates microzooplankton and mesozooplankton biomasses and chlorophyll concentrations. Thus, we propose that sufficient carbon enters the model ecosystem, but insufficient carbon is retained. For microzooplankton, the low retention of carbon could be improved by parameterizing the model with ciliate gross growth efficiency only, indicating that ciliates may contribute more to microzooplankton activity than their biomass contribution suggests. By taking into account the model underestimation of biomass, we estimate that the ocean inventory of microzooplankton biomass is 0.24 Pg C (a range of 0.14-0.33 Pg C), which is similar to the biomass of mesozooplankton.

The MarQUEST (Marine Biogeochemistry and Ecosystem Modelling Initiative in QUEST) project was established to develop improved descriptions of marine biogeochemistry, suited for the next generation of Earth system models. We review progress in these areas providing insight on the advances that have been made as well as identifying remaining key outstanding gaps for the development of the marine component of next generation Earth system models. The following issues are discussed and where appropriate results are presented; the choice of model structure, scaling processes from physiology to functional types, the ecosystem model sensitivity to changes in the physical environment, the role of the coastal ocean and new methods for the evaluation and comparison of ecosystem and biogeochemistry models. We make recommendations as to where future investment in marine ecosystem modelling should be focused, highlighting a generic software framework for model development, improved hydrodynamic models, and better parameterisation of new and existing models, reanalysis tools and ensemble simulations. The final challenge is to ensure that experimental/observational scientists are stakeholders in the models and vice versa

The oceans play a key role in climate regulation especially in part buffering (neutralising) the effects of increasing levels of greenhouse gases in the atmosphere and rising global temperatures. This chapter examines how the regulatory processes performed by the oceans alter as a response to climate change and assesses the extent to which positive feedbacks from the ocean may exacerbate climate change. There is clear evidence for rapid change in the oceans. As the main heat store for the world there has been an accelerating change in sea temperatures over the last few decades, which has contributed to rising sea-level. The oceans are also the main store of carbon dioxide (CO2), and are estimated to have taken up approximately 40% of anthropogenic-sourced CO2 from the atmosphere since the beginning of the industrial revolution. A proportion of the carbon uptake is exported via the four ocean 'carbon pumps' (Solubility, Biological, Continental Shelf and Carbonate Counter) to the deep ocean reservoir. Increases in sea temperature and changing planktonic systems and ocean currents may lead to a reduction in the uptake of CO2 by the ocean; some evidence suggests a suppression of parts of the marine carbon sink is already underway. While the oceans have buffered climate change through the uptake of CO2 produced by fossil fuel burning this has already had an impact on ocean chemistry through ocean acidification and will continue to do so. Feedbacks to climate change from acidification may result from expected impacts on marine organisms (especially corals and calcareous plankton), ecosystems and biogeochemical cycles. The polar regions of the world are showing the most rapid responses to climate change. As a result of a strong ice-ocean influence, small changes in temperature, salinity and ice cover may trigger large and sudden changes in regional climate with potential downstream feedbacks to the climate of the rest of the world. A warming Arctic Ocean may lead to furthe

Improved sampling technologies, international observing networks, and data synthesis efforts are providing an unprecedented view of the global patterns and decadal variability of surface-ocean partial pressure of carbon dioxide (pCO(2)) and air-sea CO2 flux. A new observational synthesis for surface-ocean pCO(2) leads to a global ocean net CO2 sink of -1.8 Pg C yr(-1) (+/-0.7); continental margins and estuaries together act as a small net source (similar to 0.15 Pg C yr(-1)). New results on decadal trends indicate recent decreases in efficiency of the ocean to absorb CO2 in the Southern Ocean, North Atlantic, and Equatorial Pacific. Although we do not yet have an estimate of the trend in the global oceanic sink Of CO2, the existing observations may help explain temporal variations in the fraction of anthropogenic CO2 emissions that remain in the atmosphere (airborne fraction). Major vulnerabilities in the future behavior of the ocean-carbon-climate system include the effects of ocean warming, enhanced vertical stratification, strengthening and poleward contraction of westerly winds in the Southern Ocean, and shifts in the biological pump and ecosystem functioning. To address issues of both ocean-carbon variability and vulnerability, a sustained surface-ocean-carbon-observing system needs to be established with improved global spatial coverage and internationally coordinated data synthesis activities. (C) 2009 Elsevier Ltd. All rights reserved.

The oceans play a key role in climate regulation especially in part buffering (neutralising) the effects of increasing levels of greenhouse gases in the atmosphere and rising global temperatures. This chapter examines how the regulatory processes performed by the oceans alter as a response to climate change and assesses the extent to which positive feedbacks from the ocean may exacerbate climate change. There is clear evidence for rapid change in the oceans. As the main heat store for the world there has been an accelerating change in sea temperatures over the last few decades, which has contributed to rising sea-level. The oceans are also the main store of carbon dioxide (CO2), and are estimated to have taken up 40% of anthropogenic-sourced CO2 from the atmosphere since the beginning of the industrial revolution. A proportion of the carbon uptake is exported via the four ocean ‘carbon pumps’ (Solubility, Biological, Continental Shelf and Carbonate Counter) to the deep ocean reservoir. Increases in sea temperature and changing planktonic systems and ocean currents may lead to a reduction in the uptake of CO2 by the ocean; some evidence suggests a suppression of parts of the marine carbon sink is already underway. While the oceans have buffered climate change through the uptake of CO2 produced by fossil fuel burning this has already had an impact on ocean chemistry through ocean acidification and will continue to do so. Feedbacks to climate change from acidification may result from expected impacts on marine organisms (especially corals and calcareous plankton), ecosystems and biogeochemical cycles. The polar regions of the world are showing the most rapid responses to climate change. As a result of a strong ice–ocean influence, small changes in temperature, salinity and ice cover may trigger large and sudden changes in regional climate with potential downstream feedbacks to the climate of the rest of the world. A warming Arctic Ocean may lead to further releases of

It has long been recognized that biological activity has a large influence on biogeochemical cycles in the ocean. However, the recognition that the ecosystem composition may also be significant is more recent. The newest generation of biogeochemical models used to study climate-ocean interactions represents the diversity of planktonic ecosystems by grouping similar species into “plankton functional types” (PFTs). These models can thus include specific biogeochemical processes mediated by distinct PFTs, such as the ballasting effect of mineral shells, the aggregation effect of some organic material, and the packaging effect of grazing by large zooplankton.

The ocean moderates the Earth's climate due to its vast capacity to store and transport heat; the influence of the large-scale ocean circulation on changes in climate is considered in this chapter. The ocean experiences both buoyancy forcing (through heating/cooling and evaporation/precipitation) and wind forcing. Almost all ocean forcing occurs at the surface, but these changes are communicated throughout the entire depth of the ocean through the meridional overturning circulation (MOC). In a few localized regions, water become sufficiently dense to penetrate thousands of meters deep, where it spreads, providing a continuous source of deep dense water to the entire ocean. Dense water returns to the surface and thus closes the MOC, either through density modification due to diapycnal mixing or by upwelling along sloping isopycnals across the Southern Ocean. Determination of the relative contributions of these two processes in the MOC remains an active area of research. Observations obtained primarily from isotopic compositions in ocean sediments provide substantial evidence that the structure of the MOC has changed significantly in the past. Indeed, large and abrupt changes to the Earth's climate during the past 120,000 years can be linked to either a reorganization or a complete collapse of the MOC. Two of the more dramatic instances of abrupt change include Dansgaard-Oeschger events, abrupt warmings that could exceed 10°C over a period as short as a few decades, and Heinrich events, which are associated with massive freshwater fluxes due to rapid iceberg discharges into the North Atlantic. Numerical models of varying complexity that have captured these abrupt transitions all underscore that the MOC is a highly nonlinear system with feedback loops, multiple equilibria, and hysteresis effects. Prediction of future abrupt shifts in the MOC or “tipping points” remains uncertain. However, the inferred behavior of the MOC during glacial climates suggests that significan

We quantify the relative roles of natural and anthropogenic influences on the growth rate of atmospheric CO2 and the CO2 airborne fraction, considering both interdecadal trends and interannual variability. A combined ENSO-Volcanic Index (EVI) relates most (similar to 75%) of the interannual variability in CO2 growth rate to the El-Nino-Southern-Oscillation (ENSO) climate mode and volcanic activity. Analysis of several CO2 data sets with removal of the EVI-correlated component confirms a previous finding of a detectable increasing trend in CO2 airborne fraction (defined using total anthropogenic emissions including fossil fuels and land use change) over the period 1959-2006, at a proportional growth rate 0.24% y(-1) with probability similar to 0.9 of a positive trend. This implies that the atmospheric CO2 growth rate increased slightly faster than total anthropogenic CO2 emissions. To assess the combined roles of the biophysical and anthropogenic drivers of atmospheric CO2 growth, the increase in the CO2 growth rate (1.9% y(-1) over 1959-2006) is expressed as the sum of the growth rates of four global driving factors: population (contributing + 1.7% y(-1)); per capita income (+ 1.8% y(-1)); the total carbon intensity of the global economy (-1.7% y(-1)); and airborne fraction (averaging + 0.2% y(-1) with strong interannual variability). The first three of these factors, the anthropogenic drivers, have therefore dominated the last, biophysical driver as contributors to accelerating CO2 growth. Together, the recent (post-2000) increase in growth of per capita income and decline in the negative growth (improvement) in the carbon intensity of the economy will drive a significant further acceleration in the CO2 growth rate over coming decades, unless these recent trends reverse.

We estimated a weakening of the Southern Ocean carbon dioxide (CO2) sink since 1981 relative to the trend expected from the large increase in atmospheric CO2. We agree with Law et al. that network choice increases the uncertainty of trend estimates but argue that their network of five locations is too small to be reliable. A future reversal of Southern Ocean CO2 saturation as suggested by Zickfeld et al. is possible, but only at high atmospheric CO2 concentrations, and the effect would be temporary.

The potential impact of seawater acidification on the concentrations of dimethylsulfide (DMS) and dimethylsulfoniopropionate (DMSP), and the activity of the enzyme DMSP-lyase was investigated during a pelagic ecosystem CO2 enrichment experiment (PeECE III) in spring 2005. Natural phytoplankton blooms were studied for 24 days under present, double and triple partial pressures of CO2 (pCO(2); pH=8.3, 8.0, 7.8) in triplicate 25 m(3) enclosures. The results indicate similar DMSP concentrations and DMSP-lyase activity (DLA) patterns for all treatments. Hence, DMSP and DLA do not seem to have been affected by the CO2 treatment. In contrast, DMS concentrations showed small but statistically significant differences in the temporal development of the low versus the high CO2 treatments. The low pCO(2) enclosures had higher DMS concentrations during the first 10 days, after which the levels decreased earlier and more rapidly than in the other treatments. Integrated over the whole study period, DMS concentrations were not significantly different from those of the double and triple pCO(2) treatments. Pigment and flow-cytometric data indicate that phytoplanktonic populations were generally similar between the treatments, suggesting a certain resilience of the marine ecosystem under study to the induced pH changes, which is reflected in DMSP and DLA. However, there were significant differences in bacterial community structure and the abundance of one group of viruses infecting nanoeukaryotic algae. The amount of DMS accumulated per total DMSP or chlorophyll-a differed significantly between the present and future scenarios, suggesting that the pathways for DMS production or bacterial DMS consumption were affected by seawater pH. A comparison with previous work (PeECE II) suggests that DMS concentrations do not respond consistently to pelagic ecosystem CO2 enrichment experiments

We examine ship-based observations of atmospheric O-2 and CO2 in the southern Pacific Ocean made during two voyages: in February 2003 and in April 2004. We found, for the Austral late summer to autumn, evidence of a maximum in Atmospheric Potential Oxygen (APO) (an atmospheric tracer that is conservative with respect to terrestrial biological activity, APO approximate to O-2 + CO2) centered around 50 degrees S owing to biologically driven O-2 outgassing (associated with strong productivity in the Sub-Tropical Convergence Zone) and evidence in the February voyage of a decreasing APO trend from 57 degrees S south toward the Antarctic coast. The observed APO variability appears to be primarily determined by the interplay between atmospheric transport and the spatial distribution of O-2 air-sea flux resulting from regional differences in biological production. Comparisons of these observations with APO derived from coupling the TM3 atmospheric transport model with flux estimates from (1) the PISCES-T ocean biogeochemistry model, and (2) O-2 and CO2 climatologies, show that both PISCES-T and the climatology reproduce the observed gradient and curvature of APO but underestimate the magnitude of the observed APO maximum in the mid southern latitudes. Although the temporal limitation of our data does not permit us to calculate the annual mean APO gradient, the results support previous model predictions of a decreasing APO trend from the mid to high southern latitudes.

Oceanic phytoplankton, absorbing solar radiation, can influence the bio-optical properties of seawater and hence upper ocean physics. We include this process in a global ocean general circulation model (OGCM) coupled to a dynamic green ocean model (DGOM) based on multiple plankton functional types (PFT). We not only study the impact of this process on ocean physics but we also explore the biogeochemical response due to this biophysical feedback. The phytoplankton-light feedback (PLF) impacts the dynamics of the upper tropical and subtropical oceans. The change in circulation enhances both the vertical supply in the tropics and the lateral supply of nutrients from the tropics to the subtropics boosting the subtropical productivity by up to 60 gC m(-2) a(-1). Physical changes, due to the PLF, impact on light and nutrient availability causing shifts in the ocean ecosystems. In the extratropics, increased stratification favors calcifiers (by up to similar to 8%) at the expense of mixed phytoplankton. In the Southern Ocean, silicifiers increase their biomass (by up to similar to 10%) because of the combined alleviation of iron and light limitation. The PLF has a small effect globally on air-sea fluxes of carbon dioxide (CO2, 72 TmolC a(-1) outgassing) and oxygen (O-2, 46 TmolO(2) a(-1) ingassing) because changes in biogeochemical processes (primary production, biogenic calcification, and export production) highly vary regionally and can also oppose each other. From our study it emerges that the main impact of the PLF is an amplification of the seasonal cycle of physical and biogeochemical properties of the high-latitude oceans mostly driven by the amplification of the SST seasonal cycle.

Marine ecosystems (here referring to plankton assemblages) play an important role in climate because they maintain the atmospheric concentration of CO2 at 200 ppm lower than it would be in the absence of sinking organic matter in the ocean. Marine ecosystems also form the base of the marine food chain and thereby influence the availability of food resources. Thus, changes in their structure or turnover rates could have implications for other ecosystems.