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2018
Le Quere, C, Andrew RM, Friedlingstein P, Sitch S, Hauck J, Pongratz J, Pickers PA, Korsbakken JI, Peters GP, Canadell JG, Arneth A, Arora VK, Barbero L, Bastos A, Bopp L, Chevallier F, Chini LP, Ciais P, Doney SC, Gkritzalis T, Goll DS, Harris I, Haverd V, Hoffman FM, Hoppema M, Houghton RA, Hurtt G, Ilyina T, Jain AK, Johannessen T, Jones CD, Kato E, Keeling RF, Goldewijk KK, Landschutzer P, Lefevre N, Lienert S, Liu Z, Lombardozzi D, Metzl N, Munro DR, Nabel J, Nakaoka S, Neill C, Olsen A, Ono T, Patra P, Peregon A, Peters W, Peylin P, Pfeil B, Pierrot D, Poulter B, Rehder G, Resplandy L, Robertson E, Rocher M, Rodenbeck C, Schuster U, Schwinger J, Seferian R, Skjelvan I, Steinhoff T, Sutton A, Tans PP, Tian HQ, Tilbrook B, Tubiello FN, van der Laan-Luijkx IT, van der Werf GR, Viovy N, Walker AP, Wiltshire AJ, Wright R, Zaehle S, Zheng B.  2018.  Global Carbon Budget 2018. Earth System Science Data. 10:2141-2194.   10.5194/essd-10-2141-2018   AbstractWebsite

Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere - the "global carbon budget" - is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. Fossil CO2 emissions (E-FF) are based on energy statistics and cement production data, while emissions from land use and land-use change (E-LUC), mainly deforestation, are based on land use and land -use change data and bookkeeping models. Atmospheric CO2 concentration is measured directly and its growth rate (G(ATM)) is computed from the annual changes in concentration. The ocean CO2 sink (S-OCEAN) and terrestrial CO2 sink (S-LAND) are estimated with global process models constrained by observations. The resulting carbon budget imbalance (B-IM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as +/- 1 sigma. For the last decade available (2008-2017), E-FF was 9.4 +/- 0.5 GtC yr(-1), E-LUC 1.5 +/- 0.7 GtC yr(-1), G(ATM) 4.7 +/- 0.02 GtC yr(-1), S-OCEAN 2.4 +/- 0.5 GtC yr(-1), and S-LAND 3.2 +/- 0.8 GtC yr(-1), with a budget imbalance B-IM of 0.5 GtC yr(-1) indicating overestimated emissions and/or underestimated sinks. For the year 2017 alone, the growth in E-FF was about 1.6 % and emissions increased to 9.9 +/- 0.5 GtC yr(-1). Also for 2017, E-LUC was 1.4 +/- 0.7 GtC yr(-1), G(ATM) was 4.6 +/- 0.2 GtC yr(-1), S-OCEAN was 2.5 +/- 0.5 GtC yr(-1), and S-LAND was 3.8 +/- 0.8 GtC yr(-1), with a B-IM of 0.3 GtC. The global atmospheric CO2 concentration reached 405.0 +/- 0.1 ppm averaged over 2017. For 2018, preliminary data for the first 6-9 months indicate a renewed growth in E-FF of +2.7 % (range of 1.8 % to 3.7 %) based on national emission projections for China, the US, the EU, and India and projections of gross domestic product corrected for recent changes in the carbon intensity of the economy for the rest of the world. The analysis presented here shows that the mean and trend in the five components of the global carbon budget are consistently estimated over the period of 1959-2017, but discrepancies of up to 1 GtC yr(-1) persist for the representation of semi-decadal variability in CO2 fluxes. A detailed comparison among individual estimates and the introduction of a broad range of observations show (1) no consensus in the mean and trend in land -use change emissions, (2) a persistent low agreement among the different methods on the magnitude of the land CO2 flux in the northern extra-tropics, and (3) an apparent underestimation of the CO2 variability by ocean models, originating outside the tropics. This living data update documents changes in the methods and data sets used in this new global carbon budget and the progress in understanding the global carbon cycle compared with previous publications of this data set (Le Quere et al., 2018, 2016, 2015a, b, 2014, 2013). All results presented here can be downloaded from https://doi.org/10.18160/GCP-2018.

Resplandy, L, Keeling RF, Eddebbar Y, Brooks MK, Wang R, Bopp L, Long MC, Dunne JP, Koeve W, Oschlies A.  2018.  Quantification of ocean heat uptake from changes in atmospheric O2 and CO2 composition. Nature. 563:105-108.   10.1038/s41586-018-0651-8   Abstract

The ocean is the main source of thermal inertia in the climate system1. During recent decades, ocean heat uptake has been quantified by using hydrographic temperature measurements and data from the Argo float program, which expanded its coverage after 20072,3. However, these estimates all use the same imperfect ocean dataset and share additional uncertainties resulting from sparse coverage, especially before 20074,5. Here we provide an independent estimate by using measurements of atmospheric oxygen (O2) and carbon dioxide (CO2)—levels of which increase as the ocean warms and releases gases—as a whole-ocean thermometer. We show that the ocean gained 1.33 ± 0.20  × 1022 joules of heat per year between 1991 and 2016, equivalent to a planetary energy imbalance of 0.83 ± 0.11 watts per square metre of Earth’s surface. We also find that the ocean-warming effect that led to the outgassing of O2 and CO2 can be isolated from the direct effects of anthropogenic emissions and CO2 sinks. Our result—which relies on high-precision O2 measurements dating back to 19916—suggests that ocean warming is at the high end of previous estimates, with implications for policy-relevant measurements of the Earth response to climate change, such as climate sensitivity to greenhouse gases7 and the thermal component of sea-level rise8.

Betts, RA, Jones CD, Knight JR, Keeling RF, Kennedy JJ, Wiltshire AJ, Andrew RM, Aragao L.  2018.  A successful prediction of the record CO2 rise associated with the 2015/2016 El Nino. Philosophical Transactions of the Royal Society B-Biological Sciences. 373   10.1098/rstb.2017.0301   AbstractWebsite

In early 2016, we predicted that the annual rise in carbon dioxide concentration at Mauna Loa would be the largest on record. Our forecast used a statistical relationship between observed and forecast sea surface temperatures in the Nino 3.4 region and the annual CO2 rise. Here, we provide a formal verification of that forecast. The observed rise of 3.4 ppm relative to 2015 was within the forecast range of 3.15 +/- 0.53 ppm, so the prediction was successful. A global terrestrial biosphere model supports the expectation that the El Nino weakened the tropical land carbon sink. We estimate that the El Nino contributed approximately 25% to the record rise in CO2, with 75% due to anthropogenic emissions. The 2015/2016 CO2 rise was greater than that following the previous large El Nino in 1997/1998, because anthropogenic emissions had increased. We had also correctly predicted that 2016 would be the first year with monthly mean CO2 above 400 ppm all year round. We now estimate that atmospheric CO2 at Mauna Loa would have remained above 400 ppm all year round in 2016 even if the El Nino had not occurred, contrary to our previous expectations based on a simple extrapolation of previous trends. This article is part of a discussion meeting issue 'The impact of the 2015/2016 El Nino on the terrestrial tropical carbon cycle: patterns, mechanisms and implications'.

Resplandy, L, Keeling RF, Rodenbeck C, Stephens BB, Khatiwala S, Rodgers KB, Long MC, Bopp L, Tans PP.  2018.  Revision of global carbon fluxes based on a reassessment of oceanic and riverine carbon transport. Nature Geoscience. 11:504-+.   10.1038/s41561-018-0151-3   AbstractWebsite

Measurements of atmospheric CO2 concentration provide a tight constraint on the sum of the land and ocean sinks. This constraint has been combined with estimates of ocean carbon flux and riverine transport of carbon from land to oceans to isolate the land sink. Uncertainties in the ocean and river fluxes therefore translate into uncertainties in the land sink. Here, we introduce a heat-based constraint on the latitudinal distribution of ocean and river carbon fluxes, and reassess the partition between ocean, river and land in the tropics, and in the southern and northern extra-tropics. We show that the ocean overturning circulation and biological pump tightly link the ocean transports of heat and carbon between hemispheres. Using this coupling between heat and carbon, we derive ocean and river carbon fluxes compatible with observational constraints on heat transport. This heat-based constraint requires a 20-100% stronger ocean and river carbon transport from the Northern Hemisphere to the Southern Hemisphere than existing estimates, and supports an upward revision of the global riverine carbon flux from 0.45 to 0.78 PgC yr(-1). These systematic biases in existing ocean/river carbon fluxes redistribute up to 40% of the carbon sink between northern, tropical and southern land ecosystems. As a consequence, the magnitude of both the southern land source and the northern land sink may have to be substantially reduced.

Graven, H, Fischer ML, Lueker T, Jeong S, Guilderson TP, Keeling RF, Bambha R, Brophy K, Callahan W, Cui X, Frankenberg C, Gurney KR, LaFranchi BW, Lehman SJ, Michelsen H, Miller JB, Newman S, Paplawsky W, Parazoo NC, Sloop C, Walker SJ.  2018.  Assessing fossil fuel CO2 emissions in California using atmospheric observations and models. Environmental Research Letters. 13   10.1088/1748-9326/aabd43   AbstractWebsite

Analysis systems incorporating atmospheric observations could provide a powerful tool for validating fossil fuel CO2 (ffCO(2)) emissions reported for individual regions, provided that fossil fuel sources can be separated from other CO2 sources or sinks and atmospheric transport can be accurately accounted for. We quantified ffCO(2) by measuring radiocarbon (C-14) in CO2, an accurate fossil-carbon tracer, at nine observation sites in California for three months in 2014-15. There is strong agreement between the measurements and ffCO(2) simulated using a high-resolution atmospheric model and a spatiotemporally-resolved fossil fuel flux estimate. Inverse estimates of total in-state ffCO(2) emissions are consistent with the California Air Resources Board's reported ffCO(2) emissions, providing tentative validation of California's reported ffCO(2) emissions in 2014-15. Continuing this prototype analysis system could provide critical independent evaluation of reported ffCO(2) emissions and emissions reductions in California, and the system could be expanded to other, more data-poor regions.

Le Quere, C, Andrew RM, Friedlingstein P, Sitch S, Pongratz J, Manning AC, Korsbakken JI, Peters GP, Canadell JG, Jackson RB, Boden TA, Tans PP, Andrews OD, Arora VK, Bakker DCE, Barbero L, Becker M, Betts RA, Bopp L, Chevallier F, Chini LP, Ciais P, Cosca CE, Cross J, Currie K, Gasser T, Harris I, Hauck J, Haverd V, Houghton RA, Hunt CW, Hurtt G, Ilyina T, Jain AK, Kato E, Kautz M, Keeling RF, Goldewijk KK, Kortzinger A, Landschutzer P, Lefevre N, Lenton A, Lienert S, Lima I, Lombardozzi D, Metzl N, Millero F, Monteiro PMS, Munro DR, Nabel J, Nakaoka S, Nojiri Y, Padin XA, Peregon A, Pfeil B, Pierrot D, Poulter B, Rehder G, Reimer J, Rodenbeck C, Schwinger J, Seferian R, Skjelvan I, Stocker BD, Tian HQ, Tilbrook B, Tubiello FN, van der Laan-Luijkx IT, van der Werf GR, van Heuven S, Viovy N, Vuichard N, Walker AP, Watson AJ, Wiltshire AJ, Zaehle S, Zhu D.  2018.  Global Carbon Budget 2017. Earth System Science Data. 10:405-448.   10.5194/essd-10-405-2018   AbstractWebsite

Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere - the "global carbon budget" - is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and methodology to quantify the five major components of the global carbon budget and their uncertainties. CO2 emissions from fossil fuels and industry (E-FF) are based on energy statistics and cement production data, respectively, while emissions from land-use change (E-LUC), mainly deforestation, are based on land-cover change data and bookkeeping models. The global atmospheric CO2 concentration is measured directly and its rate of growth (G(ATM)) is computed from the annual changes in concentration. The ocean CO2 sink (S-OCEAN) and terrestrial CO2 sink (S-LAND) are estimated with global process models constrained by observations. The resulting carbon budget imbalance (B-IM), the difference between the estimated total emissions and the estimated changes in the atmosphere, ocean, and terrestrial biosphere, is a measure of imperfect data and understanding of the contemporary carbon cycle. All uncertainties are reported as +/- 1 sigma. For the last decade available (2007-2016), E-FF was 9.4 +/- 0.5 GtC yr(-1), E-LUC 1.3 +/- 0.7 GtC yr(-1), G(ATM) 4.7 +/- 0.1 GtC yr(-1), S-OCEAN 2.4 +/- 0.5 GtC yr(-1), and S-LAND 3.0 +/- 0.8 GtC yr(-1), with a budget imbalance B-IM of 0.6 GtC yr(-1) indicating overestimated emissions and/or underestimated sinks. For year 2016 alone, the growth in E-FF was approximately zero and emissions remained at 9.9 +/- 0.5 GtC yr(-1). Also for 2016, E-LUC was 1.3 +/- 0.7 GtC yr(-1), G(ATM) was 6.1 +/- 0.2 GtC yr(-1), S-OCEAN was 2.6 +/- 0.5 GtC yr(-1), and S-LAND was 2.7 +/- 1.0 GtC yr(-1), with a small B-IM of 0.3 GtC. G(ATM) continued to be higher in 2016 compared to the past decade (2007-2016), reflecting in part the high fossil emissions and the small S-LAND consistent with El Nino conditions. The global atmospheric CO2 concentration reached 402.8 +/- 0.1 ppm averaged over 2016. For 2017, preliminary data for the first 6-9 months indicate a renewed growth in E-FF of +2.0% (range of 0.8 to 3.0 %) based on national emissions projections for China, USA, and India, and projections of gross domestic product (GDP) corrected for recent changes in the carbon intensity of the economy for the rest of the world. This living data update documents changes in the methods and data sets used in this new global carbon budget compared with previous publications of this data set (Le Quere et al., 2016, 2015b, a, 2014, 2013). All results presented here can be downloaded from https://doi.org/10.18160/GCP-2017 (GCP, 2017).

Stephens, BB, Long MC, Keeling RF, Kort EA, Sweeney C, Apel EC, Atlas EL, Beaton S, Bent JD, Blake NJ, Bresch JF, Casey J, Daube BC, Diao MH, Diaz E, Dierssen H, Donets V, Gao BC, Gierach M, Green R, Haag J, Hayman M, Hills AJ, Hoecker-Martinez MS, Honomichl SB, Hornbrook RS, Jensen JB, Li RR, McCubbin I, McKain K, Morgan EJ, Nolte S, Powers JG, Rainwater B, Randolph K, Reeves M, Schauffler SM, Smith K, Smith M, Stith J, Stossmeister G, Toohey DW, Watt AS.  2018.  The O-2/N-2 Ratio and CO2 Airborne Southern Ocean Study. Bulletin of the American Meteorological Society. 99:381-402.   10.1175/bams-d-16-0206.1   AbstractWebsite

The Southern Ocean plays a critical role in the global climate system by mediating atmosphere-ocean partitioning of heat and carbon dioxide. However, Earth system models are demonstrably deficient in the Southern Ocean, leading to large uncertainties in future air-sea CO2 flux projections under climate warming and incomplete interpretations of natural variability on interannual to geologic time scales. Here, we describe a recent aircraft observational campaign, the O-2/N-2 Ratio and CO2 Airborne Southern Ocean (ORCAS) study, which collected measurements over the Southern Ocean during January and February 2016. The primary research objective of the ORCAS campaign was to improve observational constraints on the seasonal exchange of atmospheric carbon dioxide and oxygen with the Southern Ocean. The campaign also included measurements of anthropogenic and marine biogenic reactive gases; high-resolution, hyperspectral ocean color imaging of the ocean surface; and microphysical data relevant for understanding and modeling cloud processes. In each of these components of the ORCAS project, the campaign has significantly expanded the amount of observational data available for this remote region. Ongoing research based on these observations will contribute to advancing our understanding of this climatically important system across a range of topics including carbon cycling, atmospheric chemistry and transport, and cloud physics. This article presents an overview of the scientific and methodological aspects of the ORCAS project and highlights early findings.

2017
Keeling, RF, Graven HD, Welp LR, Resplandy L, Bi J, Piper SC, Sun Y, Bollenbacher A, Meijer HAJ.  2017.  Atmospheric evidence for a global secular increase in carbon isotopic discrimination of land photosynthesis. Proceedings of the National Academy of Sciences of the United States of America. 114:10361-10366.   10.1073/pnas.1619240114   AbstractWebsite

A decrease in the C-13/C-12 ratio of atmospheric CO2 has been documented by direct observations since 1978 and from ice core measurements since the industrial revolution. This decrease, known as the C-13-Suess effect, is driven primarily by the input of fossil fuel-derived CO2 but is also sensitive to land and ocean carbon cycling and uptake. Using updated records, we show that no plausible combination of sources and sinks of CO2 from fossil fuel, land, and oceans can explain the observed C-13-Suess effect unless an increase has occurred in the C-13/C-12 isotopic discrimination of land photosynthesis. A trend toward greater discrimination under higher CO2 levels is broadly consistent with tree ring studies over the past century, with field and chamber experiments, and with geological records of C-3 plants at times of altered atmospheric CO2, but increasing discrimination has not previously been included in studies of long-term atmospheric 13C/12C measurements. We further show that the inferred discrimination increase of 0.014 +/- 0.007% ppm(-1) is largely explained by photorespiratory and mesophyll effects. This result implies that, at the global scale, land plants have regulated their stomatal conductance so as to allow the CO2 partial pressure within stomatal cavities and their intrinsic water use efficiency to increase in nearly constant proportion to the rise in atmospheric CO2 concentration.

Fischer, ML, Parazoo N, Brophy K, Cui XG, Jeong S, Liu JJ, Keeling R, Taylor TE, Gurney K, Oda T, Graven H.  2017.  Simulating estimation of California fossil fuel and biosphere carbon dioxide exchanges combining in situ tower and satellite column observations. Journal of Geophysical Research-Atmospheres. 122:3653-3671.   10.1002/2016jd025617   AbstractWebsite

We report simulation experiments estimating the uncertainties in California regional fossil fuel and biosphere CO2 exchanges that might be obtained by using an atmospheric inverse modeling system driven by the combination of ground-based observations of radiocarbon and total CO2, together with column-mean CO2 observations from NASA's Orbiting Carbon Observatory (OCO-2). The work includes an initial examination of statistical uncertainties in prior models for CO2 exchange, in radiocarbon-based fossil fuel CO2 measurements, in OCO-2 measurements, and in a regional atmospheric transport modeling system. Using these nominal assumptions for measurement and model uncertainties, we find that flask measurements of radiocarbon and total CO2 at 10 towers can be used to distinguish between different fossil fuel emission data products for major urban regions of California. We then show that the combination of flask and OCO-2 observations yields posterior uncertainties in monthly-mean fossil fuel emissions of similar to 5-10%, levels likely useful for policy relevant evaluation of bottom-up fossil fuel emission estimates. Similarly, we find that inversions yield uncertainties in monthly biosphere CO2 exchange of similar to 6%-12%, depending on season, providing useful information on net carbon uptake in California's forests and agricultural lands. Finally, initial sensitivity analysis suggests that obtaining the above results requires control of systematic biases below approximately 0.5ppm, placing requirements on accuracy of the atmospheric measurements, background subtraction, and atmospheric transport modeling.

2016
Resplandy, L, Keeling RF, Stephens BB, Bent JD, Jacobson A, Rodenbeck C, Khatiwala S.  2016.  Constraints on oceanic meridional heat transport from combined measurements of oxygen and carbon. Climate Dynamics. 47:3335-3357.   10.1007/s00382-016-3029-3   AbstractWebsite

Despite its importance to the climate system, the ocean meridional heat transport is still poorly quantified. We identify a strong link between the northern hemisphere deficit in atmospheric potential oxygen (APO = O + 1.1 CO) and the asymmetry in meridional heat transport between northern and southern hemispheres. The recent aircraft observations from the HIPPO campaign reveal a northern APO deficit in the tropospheric column of 10.4 1.0 per meg, double the value at the surface and more representative of large-scale air-sea fluxes. The global northward ocean heat transport asymmetry necessary to explain the observed APO deficit is about 0.7-1.1 PW, which corresponds to the upper range of estimates from hydrographic sections and atmospheric reanalyses.

Jeong, SG, Newman S, Zhang JS, Andrews AE, Bianco L, Bagley J, Cui XG, Graven H, Kim J, Salameh P, LaFranchi BW, Priest C, Campos-Pineda M, Novakovskaia E, Sloop CD, Michelsen HA, Bambha RP, Weiss RF, Keeling R, Fischer ML.  2016.  Estimating methane emissions in California's urban and rural regions using multitower observations. Journal of Geophysical Research-Atmospheres. 121:13031-13049.   10.1002/2016jd025404   AbstractWebsite

We present an analysis of methane (CH4) emissions using atmospheric observations from 13 sites in California during June 2013 to May 2014. A hierarchical Bayesian inversion method is used to estimate CH4 emissions for spatial regions (0.3 degrees pixels for major regions) by comparing measured CH4 mixing ratios with transport model (Weather Research and Forecasting and Stochastic Time-Inverted Lagrangian Transport) predictions based on seasonally varying California-specific CH4 prior emission models. The transport model is assessed using a combination of meteorological and carbon monoxide (CO) measurements coupled with the gridded California Air Resources Board (CARB) CO emission inventory. The hierarchical Bayesian inversion suggests that state annual anthropogenic CH4 emissions are 2.42 +/- 0.49 Tg CH4/yr (at 95% confidence), higher (1.2-1.8 times) than the current CARB inventory (1.64 Tg CH4/yr in 2013). It should be noted that undiagnosed sources of errors or uncaptured errors in the model-measurement mismatch covariance may increase these uncertainty bounds beyond that indicated here. The CH4 emissions from the Central Valley and urban regions (San Francisco Bay and South Coast Air Basins) account for similar to 58% and 26% of the total posterior emissions, respectively. This study suggests that the livestock sector is likely the major contributor to the state total CH4 emissions, in agreement with CARB's inventory. Attribution to source sectors for subregions of California using additional trace gas species would further improve the quantification of California's CH4 emissions and mitigation efforts toward the California Global Warming Solutions Act of 2006 (Assembly Bill 32).

Le Quere, C, Andrew RM, Canadell JG, Sitch S, Korsbakken JI, Peters GP, Manning AC, Boden TA, Tans PP, Houghton RA, Keeling RF, Alin S, Andrews OD, Anthoni P, Barbero L, Bopp L, Chevallier F, Chini LP, Ciais P, Currie K, Delire C, Doney SC, Friedlingstein P, Gkritzalis T, Harris I, Hauck J, Haverd V, Hoppema M, Goldewijk KK, Jain AK, Kato E, Kortzinger A, Landschutzer P, Lefevre N, Lenton A, Lienert S, Lombardozzi D, Melton JR, Metzl N, Millero F, Monteiro PMS, Munro DR, Nabel J, Nakaoka S, O'Brien K, Olsen A, Omar AM, Ono T, Pierrot D, Poulter B, Rodenbeck C, Salisbury J, Schuster U, Schwinger J, Seferian R, Skjelvan I, Stocker BD, Sutton AJ, Takahashi T, Tian HQ, Tilbrook B, van der Laan-Luijkx IT, van der Werf GR, Viovy N, Walker AP, Wiltshire AJ, Zaehle S.  2016.  Global Carbon Budget 2016. Earth System Science Data. 8:605-649.   10.5194/essd-8-605-2016   AbstractWebsite

Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere - the "global carbon budget" - is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and methodology to quantify all major components of the global carbon budget, including their uncertainties, based on the combination of a range of data, algorithms, statistics, and model estimates and their interpretation by a broad scientific community. We discuss changes compared to previous estimates and consistency within and among components, alongside methodology and data limitations. CO2 emissions from fossil fuels and industry (E-FF) are based on energy statistics and cement production data, respectively, while emissions from land-use change (E-LUC), mainly deforestation, are based on combined evidence from land-cover change data, fire activity associated with deforestation, and models. The global atmospheric CO2 concentration is measured directly and its rate of growth (G(ATM)) is computed from the annual changes in concentration. The mean ocean CO2 sink (S-OCEAN) is based on observations from the 1990s, while the annual anomalies and trends are estimated with ocean models. The variability in S-OCEAN is evaluated with data products based on surveys of ocean CO2 measurements. The global residual terrestrial CO2 sink (S-LAND) is estimated by the difference of the other terms of the global carbon budget and compared to results of independent dynamic global vegetation models. We compare the mean land and ocean fluxes and their variability to estimates from three atmospheric inverse methods for three broad latitude bands. All uncertainties are reported as +/- 1 sigma, reflecting the current capacity to characterise the annual estimates of each component of the global carbon budget. For the last decade available (2006-2015), E-FF was 9.3 +/- 0.5 GtC yr(-1), E-LUC 1.0 +/- 0.5 GtC yr(-1), G(ATM) 4.5 +/- 0.1 GtC yr(-1), S-OCEAN 2.6 +/- 0.5 GtC yr(-1), and S-LAND 3.1 +/- 0.9 GtC yr(-1). For year 2015 alone, the growth in E-FF was approximately zero and emissions remained at 9.9 +/- 0.5 GtC yr(-1), showing a slowdown in growth of these emissions compared to the average growth of 1.8% yr(-1) that took place during 2006-2015. Also, for 2015, E-LUC was 1.3 +/- 0.5 GtC yr(-1), G(ATM) was 6.3 +/- 0.2 GtC yr(-1), S-OCEAN was 3.0 +/- 0.5 GtC yr(-1), and S-LAND was 1.9 +/- 0.9 GtC yr(-1). G(ATM) was higher in 2015 compared to the past decade (2006-2015), reflecting a smaller S-LAND for that year. The global atmospheric CO2 concentration reached 399.4 +/- 0.1 ppm averaged over 2015. For 2016, preliminary data indicate the continuation of low growth in E-FF with +0.2% (range of -1.0 to +1.8 %) based on national emissions projections for China and USA, and projections of gross domestic product corrected for recent changes in the carbon intensity of the economy for the rest of the world. In spite of the low growth of E-FF in 2016, the growth rate in atmospheric CO2 concentration is expected to be relatively high because of the persistence of the smaller residual terrestrial sink (S-LAND) in response to El Nino conditions of 2015-2016. From this projection of E-FF and assumed constant E-LUC for 2016, cumulative emissions of CO2 will reach 565 +/- 55 GtC (2075 +/- 205 GtCO(2)) for 1870-2016, about 75% from E-FF and 25% from E-LUC. This living data update documents changes in the methods and data sets used in this new carbon budget compared with previous publications of this data set (Le Quere et al., 2015b, a, 2014, 2013). All observations presented here can be downloaded from the Carbon Dioxide Information Analysis Center (doi: 10.3334/CDIAC/GCP_2016).

Welp, LR, Patra PK, Rodenbeck C, Nemani R, Bi J, Piper SC, Keeling RF.  2016.  Increasing summer net CO2 uptake in high northern ecosystems inferred from atmospheric inversions and comparisons to remote-sensing NDVI. Atmospheric Chemistry and Physics. 16:9047-9066.   10.5194/acp-16-9047-2016   AbstractWebsite

Warmer temperatures and elevated atmospheric CO2 concentrations over the last several decades have been credited with increasing vegetation activity and photosynthetic uptake of CO2 from the atmosphere in the high northern latitude ecosystems: the boreal forest and arctic tundra. At the same time, soils in the region have been warming, permafrost is melting, fire frequency and severity are increasing, and some regions of the boreal forest are showing signs of stress due to drought or insect disturbance. The recent trends in net carbon balance of these ecosystems, across heterogeneous disturbance patterns, and the future implications of these changes are unclear. Here, we examine CO2 fluxes from northern boreal and tundra regions from 1985 to 2012, estimated from two atmospheric inversions (RIGC and Jena). Both used measured atmospheric CO2 concentrations and wind fields from interannually variable climate reanalysis. In the arctic zone, the latitude region above 60 degrees N excluding Europe (10 degrees W-63 degrees E), neither inversion finds a significant long-term trend in annual CO2 balance. The boreal zone, the latitude region from approximately 50-60 degrees N, again excluding Europe, showed a trend of 8-11 Tg C yr(-2) over the common period of validity from 1986 to 2006, resulting in an annual CO2 sink in 2006 that was 170-230 Tg C yr(-1) larger than in 1986. This trend appears to continue through 2012 in the Jena inversion as well. In both latitudinal zones, the seasonal amplitude of monthly CO2 fluxes increased due to increased uptake in summer, and in the arctic zone also due to increased fall CO2 release. These findings suggest that the boreal zone has been maintaining and likely increasing CO2 sink strength over this period, despite browning trends in some regions and changes in fire frequency and land use. Meanwhile, the arctic zone shows that increased summer CO2 uptake, consistent with strong greening trends, is offset by increased fall CO2 release, resulting in a net neutral trend in annual fluxes. The inversion fluxes from the arctic and boreal zones covering the permafrost regions showed no indication of a large-scale positive climate-carbon feedback caused by warming temperatures on high northern latitude terrestrial CO2 fluxes from 1985 to 2012.

Nevison, CD, Manizza M, Keeling RF, Stephens BB, Bent JD, Dunne J, Ilyina T, Long M, Resplandy L, Tjiputra J, Yukimoto S.  2016.  Evaluating CMIP5 ocean biogeochemistry and Southern Ocean carbon uptake using atmospheric potential oxygen: Present-day performance and future projection. Geophysical Research Letters. 43:2077-2085.   10.1002/2015gl067584   AbstractWebsite

Observed seasonal cycles in atmospheric potential oxygen (APO similar to O-2+1.1 CO2) were used to evaluate eight ocean biogeochemistry models from the Coupled Model Intercomparison Project (CMIP5). Model APO seasonal cycles were computed from the CMIP5 air-sea O-2 and CO2 fluxes and compared to observations at three Southern Hemisphere monitoring sites. Four of the models captured either the observed APO seasonal amplitude or phasing relatively well, while the other four did not. Many models had an unrealistic seasonal phasing or amplitude of the CO2 flux, which in turn influenced APO. By 2100 under RCP8.5, the models projected little change in the O-2 component of APO but large changes in the seasonality of the CO2 component associated with ocean acidification. The models with poorer performance on present-day APO tended to project larger net carbon uptake in the Southern Ocean, both today and in 2100.

Petrenko, VV, Severinghaus JP, Schaefer H, Smith AM, Kuhl T, Baggenstos D, Hua Q, Brook EJ, Rose P, Kulin R, Bauska T, Harth C, Buizert C, Orsi A, Emanuele G, Lee JE, Brailsford G, Keeling R, Weiss RF.  2016.  Measurements of 14C in ancient ice from Taylor Glacier, Antarctica constrain in situ cosmogenic 14CH4 and 14CO production rates. Geochimica et Cosmochimica Acta. 177:62-77.   10.1016/j.gca.2016.01.004   Abstract

Carbon-14 (14C) is incorporated into glacial ice by trapping of atmospheric gases as well as direct near-surface in situ cosmogenic production. 14C of trapped methane (14CH4) is a powerful tracer for past CH4 emissions from “old” carbon sources such as permafrost and marine CH4 clathrates. 14C in trapped carbon dioxide (14CO2) can be used for absolute dating of ice cores. In situ produced cosmogenic 14C in carbon monoxide (14CO) can potentially be used to reconstruct the past cosmic ray flux and past solar activity. Unfortunately, the trapped atmospheric and in situ cosmogenic components of 14C in glacial ice are difficult to disentangle and a thorough understanding of the in situ cosmogenic component is needed in order to extract useful information from ice core 14C. We analyzed very large (≈1000 kg) ice samples in the 2.26–19.53 m depth range from the ablation zone of Taylor Glacier, Antarctica, to study in situ cosmogenic production of 14CH4 and 14CO. All sampled ice is >50 ka in age, allowing for the assumption that most of the measured 14C originates from recent in situ cosmogenic production as ancient ice is brought to the surface via ablation. Our results place the first constraints on cosmogenic 14CH4 production rates and improve on prior estimates of 14CO production rates in ice. We find a constant 14CH4/14CO production ratio (0.0076 ± 0.0003) for samples deeper than 3 m, which allows the use of 14CO for correcting the 14CH4 signals for the in situ cosmogenic component. Our results also provide the first unambiguous confirmation of 14C production by fast muons in a natural setting (ice or rock) and suggest that the 14C production rates in ice commonly used in the literature may be too high.

2015
Le Quere, C, Moriarty R, Andrew RM, Canadell JG, Sitch S, Korsbakken JI, Friedlingstein P, Peters GP, Andres RJ, Boden TA, Houghton RA, House JI, Keeling RF, Tans P, Arneth A, Bakker DCE, Barbero L, Bopp L, Chang J, Chevallier F, Chini LP, Ciais P, Fader M, Feely RA, Gkritzalis T, Harris I, Hauck J, Ilyina T, Jain AK, Kato E, Kitidis V, Goldewijk KK, Koven C, Landschutzer P, Lauvset SK, Lefevre N, Lenton A, Lima ID, Metzl N, Millero F, Munro DR, Murata A, Nabel J, Nakaoka S, Nojiri Y, O'Brien K, Olsen A, Ono T, Perez FF, Pfeil B, Pierrot D, Poulter B, Rehder G, Rodenbeck C, Saito S, Schuster U, Schwinger J, Seferian R, Steinhoff T, Stocker BD, Sutton AJ, Takahashi T, Tilbrook B, van der Laan-Luijkx IT, van der Werf GR, van Heuven S, Vandemark D, Viovy N, Wiltshire A, Zaehle S, Zeng N.  2015.  Global Carbon Budget 2015. Earth System Science Data. 7:349-396.   10.5194/essd-7-349-2015   AbstractWebsite

Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and a methodology to quantify all major components of the global carbon budget, including their uncertainties, based on the combination of a range of data, algorithms, statistics, and model estimates and their interpretation by a broad scientific community. We discuss changes compared to previous estimates as well as consistency within and among components, alongside methodology and data limitations. CO2 emissions from fossil fuels and industry (E-FF) are based on energy statistics and cement production data, while emissions from land-use change (E-LUC), mainly deforestation, are based on combined evidence from land-cover-change data, fire activity associated with deforestation, and models. The global atmospheric CO2 concentration is measured directly and its rate of growth (G(ATM)) is computed from the annual changes in concentration. The mean ocean CO2 sink (S-OCEAN) is based on observations from the 1990s, while the annual anomalies and trends are estimated with ocean models. The variability in S-OCEAN is evaluated with data products based on surveys of ocean CO2 measurements. The global residual terrestrial CO2 sink (S-LAND) is estimated by the difference of the other terms of the global carbon budget and compared to results of independent dynamic global vegetation models forced by observed climate, CO2, and land-cover change (some including nitrogen-carbon interactions). We compare the mean land and ocean fluxes and their variability to estimates from three atmospheric inverse methods for three broad latitude bands. All uncertainties are reported as +/- 1 sigma, reflecting the current capacity to characterise the annual estimates of each component of the global carbon budget. For the last decade available (20052014), E-FF was 9.0 +/- 0.5 GtC yr(-1) E-LUC was 0.9 +/- 0.5 GtC yr(-1), GATM was 4.4 +/- 0.1 GtC yr(-1), S-OCEAN was 2.6 +/- 0.5 GtC yr(-1), and S LAND was 3.0 +/- 0.8 GtC yr(-1). For the year 2014 alone, E FF grew to 9.8 +/- 0.5 GtC yr(-1), 0.6% above 2013, continuing the growth trend in these emissions, albeit at a slower rate compared to the average growth of 2.2% yr(-1) that took place during 2005-2014. Also, for 2014, E-LUC was 1.1 +/- 0.5 GtC yr(-1), G(ATM) was 3.9 +/- 0.2 GtC yr(-1), S-OCEAN was 2.9 +/- 0.5 GtC yr(-1), and S-LAND was 4.1 +/- 0.9 GtC yr(-1). G(ATM) was lower in 2014 compared to the past decade (2005-2014), reflecting a larger S-LAND for that year. The global atmospheric CO2 concentration reached 397.15 +/- 0.10 ppm averaged over 2014. For 2015, preliminary data indicate that the growth in E-FF will be near or slightly below zero, with a projection of 0.6 [ range of 1.6 to C 0.5] %, based on national emissions projections for China and the USA, and projections of gross domestic product corrected for recent changes in the carbon intensity of the global economy for the rest of the world. From this projection of E-FF and assumed constant E LUC for 2015, cumulative emissions of CO2 will reach about 555 +/- 55 GtC (2035 +/- 205 GtCO(2)) for 1870-2015, about 75% from E FF and 25% from E LUC. This living data update documents changes in the methods and data sets used in this new carbon budget compared with previous publications of this data set (Le Quere et al., 2015, 2014, 2013). All observations presented here can be downloaded from the Carbon Dioxide Information Analysis Center (doi: 10.3334/CDIAC/GCP_2015).

Lucas, DD, Yver Kwok C, Cameron-Smith P, Graven H, Bergmann D, Guilderson TP, Weiss R, Keeling R.  2015.  Designing optimal greenhouse gas observing networks that consider performance and cost. Geosci. Instrum. Method. Data Syst.. 4:121-137.: Copernicus Publications   10.5194/gi-4-121-2015   AbstractWebsite
n/a
Le Quere, C, Moriarty R, Andrew RM, Peters GP, Ciais P, Friedlingstein P, Jones SD, Sitch S, Tans P, Arneth A, Boden TA, Bopp L, Bozec Y, Canadell JG, Chini LP, Chevallier F, Cosca CE, Harris I, Hoppema M, Houghton RA, House JI, Jain AK, Johannessen T, Kato E, Keeling RF, Kitidis V, Goldewijk KK, Koven C, Landa CS, Landschutzer P, Lenton A, Lima ID, Marland G, Mathis JT, Metzl N, Nojiri Y, Olsen A, Ono T, Peng S, Peters W, Pfeil B, Poulter B, Raupach MR, Regnier P, Rodenbeck C, Saito S, Salisbury JE, Schuster U, Schwinger J, Seferian R, Segschneider J, Steinhoff T, Stocker BD, Sutton AJ, Takahashi T, Tilbrook B, van der Werf GR, Viovy N, Wang YP, Wanninkhof R, Wiltshire A, Zeng N.  2015.  Global carbon budget 2014. Earth System Science Data. 7:47-85.   10.5194/essd-7-47-2015   AbstractWebsite

Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and a methodology to quantify all major components of the global carbon budget, including their uncertainties, based on the combination of a range of data, algorithms, statistics, and model estimates and their interpretation by a broad scientific community. We discuss changes compared to previous estimates, consistency within and among components, alongside methodology and data limitations. CO2 emissions from fossil fuel combustion and cement production (E-FF) are based on energy statistics and cement production data, respectively, while emissions from land-use change (E-LUC), mainly deforestation, are based on combined evidence from land-cover-change data, fire activity associated with deforestation, and models. The global atmospheric CO2 concentration is measured directly and its rate of growth (G(ATM)) is computed from the annual changes in concentration. The mean ocean CO2 sink (S-OCEAN) is based on observations from the 1990s, while the annual anomalies and trends are estimated with ocean models. The variability in S-OCEAN is evaluated with data products based on surveys of ocean CO2 measurements. The global residual terrestrial CO2 sink (S-LAND) is estimated by the difference of the other terms of the global carbon budget and compared to results of independent dynamic global vegetation models forced by observed climate, CO2, and land-cover-change (some including nitrogen-carbon interactions). We compare the mean land and ocean fluxes and their variability to estimates from three atmospheric inverse methods for three broad latitude bands. All uncertainties are reported as +/- 1 sigma, reflecting the current capacity to characterise the annual estimates of each component of the global carbon budget. For the last decade available (2004-2013), E-FF was 8.9 +/- 0.4 GtC yr(-1), E-LUC 0.9 +/- 0.5 GtC yr(-1), G(ATM) 4.3 +/- 0.1 GtC yr(-1), S-OCEAN 2.6 +/- 0.5 GtC yr(-1), and S-LAND 2.9 +/- 0.8 GtC yr(-1). For year 2013 alone, E-FF grew to 9.9 +/- 0.5 GtC yr(-1), 2.3% above 2012, continuing the growth trend in these emissions, E-LUC was 0.9 +/- 0.5 GtC yr(-1), G(ATM) was 5.4 +/- 0.2 GtC yr(-1), S-OCEAN was 2.9 +/- 0.5 GtC yr(-1), and S-LAND was 2.5 +/- 0.9 GtC yr(-1). G(ATM) was high in 2013, reflecting a steady increase in E-FF and smaller and opposite changes between S-OCEAN and S-LAND compared to the past decade (2004-2013). The global atmospheric CO2 concentration reached 395.31 +/- 0.10 ppm averaged over 2013. We estimate that E-FF will increase by 2.5% (1.3-3.5 %) to 10.1 +/- 0.6 GtC in 2014 (37.0 +/- 2.2 GtCO(2) yr(-1)), 65% above emissions in 1990, based on projections of world gross domestic product and recent changes in the carbon intensity of the global economy. From this projection of E-FF and assumed constant E-LUC for 2014, cumulative emissions of CO2 will reach about 545 +/- 55 GtC (2000 +/- 200 GtCO(2)) for 1870-2014, about 75% from E-FF and 25% from E-LUC. This paper documents changes in the methods and data sets used in this new carbon budget compared with previous publications of this living data set (Le Quere et al., 2013, 2014). All observations presented here can be downloaded from the Carbon Dioxide Information Analysis Center (doi:10.3334/CDIAC/GCP_2014).

2014
Le Quere, C, Peters GP, Andres RJ, Andrew RM, Boden TA, Ciais P, Friedlingstein P, Houghton RA, Marland G, Moriarty R, Sitch S, Tans P, Arneth A, Arvanitis A, Bakker DCE, Bopp L, Canadell JG, Chini LP, Doney SC, Harper A, Harris I, House JI, Jain AK, Jones SD, Kato E, Keeling RF, Goldewijk KK, Kortzinger A, Koven C, Lefevre N, Maignan F, Omar A, Ono T, Park GH, Pfeil B, Poulter B, Raupach MR, Regnier P, Rodenbeck C, Saito S, Schwinger J, Segschneider J, Stocker BD, Takahashi T, Tilbrook B, van Heuven S, Viovy N, Wanninkhof R, Wiltshire A, Zaehle S.  2014.  Global carbon budget 2013. Earth System Science Data. 6:235-263.   10.5194/essd-6-235-2014   AbstractWebsite

Accurate assessment of anthropogenic carbon dioxide (CO2) emissions and their redistribution among the atmosphere, ocean, and terrestrial biosphere is important to better understand the global carbon cycle, support the development of climate policies, and project future climate change. Here we describe data sets and a methodology to quantify all major components of the global carbon budget, including their uncertainties, based on the combination of a range of data, algorithms, statistics and model estimates and their interpretation by a broad scientific community. We discuss changes compared to previous estimates, consistency within and among components, alongside methodology and data limitations. CO2 emissions from fossil-fuel combustion and cement production (E-FF) are based on energy statistics, while emissions from land-use change (E-LUC), mainly deforestation, are based on combined evidence from land-cover change data, fire activity associated with deforestation, and models. The global atmospheric CO2 concentration is measured directly and its rate of growth (G(ATM)) is computed from the annual changes in concentration. The mean ocean CO2 sink (S-OCEAN) is based on observations from the 1990s, while the annual anomalies and trends are estimated with ocean models. The variability in SOCEAN is evaluated for the first time in this budget with data products based on surveys of ocean CO2 measurements. The global residual terrestrial CO2 sink (S-LAND) is estimated by the difference of the other terms of the global carbon budget and compared to results of independent dynamic global vegetation models forced by observed climate, CO2 and land cover change (some including nitrogen-carbon interactions). All uncertainties are reported as +/- 1 sigma, reflecting the current capacity to characterise the annual estimates of each component of the global carbon budget. For the last decade available (2003-2012), E-FF was 8.6 +/- 0.4 GtC yr(-1), E-LUC 0.9 +/- 0.5 GtC yr(-1), G(ATM) 4.3 +/- 0.1 GtC yr(-1), S-OCEAN 2.5 +/- 0.5 GtC yr(-1), and S-LAND 2.8 +/- 0.8 GtC yr(-1). For year 2012 alone, E-FF grew to 9.7 +/- 0.5 GtC yr(-1), 2.2% above 2011, reflecting a continued growing trend in these emissions, GATM was 5.1 +/- 0.2 GtC yr(-1), S-OCEAN was 2.9 +/- 0.5 GtC yr(-1), and assuming an E-LUC of 1.0 +/- 0.5 GtC yr(-1) (based on the 2001-2010 average), S-LAND was 2.7 +/- 0.9 GtC yr(-1). G(ATM) was high in 2012 compared to the 2003-2012 average, almost entirely reflecting the high EFF. The global atmospheric CO2 concentration reached 392.52 +/- 0.10 ppm averaged over 2012. We estimate that E-FF will increase by 2.1% (1.1-3.1 %) to 9.9 +/- 0.5 GtC in 2013, 61% above emissions in 1990, based on projections of world gross domestic product and recent changes in the carbon intensity of the economy. With this projection, cumulative emissions of CO2 will reach about 535 +/- 55 GtC for 1870-2013, about 70% from E-FF (390 +/- 20 GtC) and 30% from E-LUC (145 +/- 50 GtC). This paper also documents any changes in the methods and data sets used in this new carbon budget from previous budgets (Le Quere et al., 2013). All observations presented here can be downloaded from the Carbon Dioxide Information Analysis Center (doi: 10.3334/CDIAC/GCP_2013_V2.3).

Rodenbeck, C, Bakker DCE, Metzl N, Olsen A, Sabine C, Cassar N, Reum F, Keeling RF, Heimann M.  2014.  Interannual sea-air CO2 flux variability from an observation-driven ocean mixed-layer scheme. Biogeosciences. 11:4599-4613.   10.5194/bg-11-4599-2014   AbstractWebsite

Interannual anomalies in the sea-air carbon dioxide (CO2) exchange have been estimated from surface-ocean CO2 partial pressure measurements. Available data are sufficient to constrain these anomalies in large parts of the tropical and North Pacific and in the North Atlantic, in some areas covering the period from the mid 1980s to 2011. Global interannual variability is estimated as about 0.31 Pg Cyr(-1) (temporal standard deviation 1993-2008). The tropical Pacific accounts for a large fraction of this global variability, closely tied to El Ni o-Southern Oscillation (ENSO). Anomalies occur more than 6 months later in the east than in the west. The estimated amplitude and ENSO response are roughly consistent with independent information from atmospheric oxygen data. This both supports the variability estimated from surface-ocean carbon data and demonstrates the potential of the atmospheric oxygen signal to constrain ocean biogeochemical processes. The ocean variability estimated from surface-ocean carbon data can be used to improve land CO2 flux estimates from atmospheric inversions.

Rodgers, KB, Aumont O, Fletcher SEM, Plancherel Y, Bopp L, Montegut CD, Iudicone D, Keeling RF, Madec G, Wanninkhof R.  2014.  Strong sensitivity of Southern Ocean carbon uptake and nutrient cycling to wind stirring. Biogeosciences. 11:4077-4098.   10.5194/bg-11-4077-2014   AbstractWebsite

Here we test the hypothesis that winds have an important role in determining the rate of exchange of CO2 between the atmosphere and ocean through wind stirring over the Southern Ocean. This is tested with a sensitivity study using an ad hoc parameterization of wind stirring in an ocean carbon cycle model, where the objective is to identify the way in which perturbations to the vertical density structure of the planetary boundary in the ocean impacts the carbon cycle and ocean biogeochemistry. Wind stirring leads to reduced uptake of CO2 by the Southern Ocean over the period 2000-2006, with a relative reduction with wind stirring on the order of 0.9 Pg C yr(-1) over the region south of 45 degrees S. This impacts not only the mean carbon uptake, but also the phasing of the seasonal cycle of carbon and other ocean biogeochemical tracers. Enhanced wind stirring delays the seasonal onset of stratification, and this has large impacts on both entrainment and the biological pump. It is also found that there is a strong reduction on the order of 25-30% in the concentrations of NO3 exported in Subantarctic Mode Water (SAMW) to wind stirring. This finds expression not only locally over the Southern Ocean, but also over larger scales through the impact on advected nutrients. In summary, the large sensitivity identified with the ad hoc wind stirring parameterization offers support for the importance of wind stirring for global ocean biogeochemistry through its impact over the Southern Ocean.

2013
Graven, HD, Keeling RF, Piper SC, Patra PK, Stephens BB, Wofsy SC, Welp LR, Sweeney C, Tans PP, Kelley JJ, Daube BC, Kort EA, Santoni GW, Bent JD.  2013.  Enhanced seasonal exchange of CO2 by northern ecosystems since 1960. Science. 341:1085-1089.   10.1126/science.1239207   AbstractWebsite

Seasonal variations of atmospheric carbon dioxide (CO2) in the Northern Hemisphere have increased since the 1950s, but sparse observations have prevented a clear assessment of the patterns of long-term change and the underlying mechanisms. We compare recent aircraft-based observations of CO2 above the North Pacific and Arctic Oceans to earlier data from 1958 to 1961 and find that the seasonal amplitude at altitudes of 3 to 6 km increased by 50% for 45 degrees to 90 degrees N but by less than 25% for 10 degrees to 45 degrees N. An increase of 30 to 60% in the seasonal exchange of CO2 by northern extratropical land ecosystems, focused on boreal forests, is implicated, substantially more than simulated by current land ecosystem models. The observations appear to signal large ecological changes in northern forests and a major shift in the global carbon cycle.

Rodenbeck, C, Keeling RF, Bakker DCE, Metz N, Olsen A, Sabine C, Heimann M.  2013.  Global surface-ocean p(CO2) and sea-air CO2 flux variability from an observation-driven ocean mixed-layer scheme. Ocean Science. 9:193-216.   10.5194/os-9-193-2013   AbstractWebsite

A temporally and spatially resolved estimate of the global surface-ocean CO2 partial pressure field and the sea air CO2 flux is presented, obtained by fitting a simple data-driven diagnostic model of ocean mixed-layer biogeochemistry to surface-ocean CO2 partial pressure data from the SOCAT v1.5 database. Results include seasonal, interannual, and short-term (daily) variations. In most regions, estimated seasonality is well constrained from the data, and compares well to the widely used monthly climatology by Takahashi et al. (2009). Comparison to independent data tentatively supports the slightly higher seasonal variations in our estimates in some areas. We also fitted the diagnostic model to atmospheric CO2 data. The results of this are less robust, but in those areas where atmospheric signals are not strongly influenced by land flux variability, their seasonality is nevertheless consistent with the results based on surface-ocean data. From a comparison with an independent seasonal climatology of surface-ocean nutrient concentration, the diagnostic model is shown to capture relevant surface-ocean biogeochemical processes reasonably well. Estimated interannual variations will be presented and discussed in a companion paper.

2011
Welp, LR, Keeling RF, Meijer HAJ, Bollenbacher AF, Piper SC, Yoshimura K, Francey RJ, Allison CE, Wahlen M.  2011.  Interannual variability in the oxygen isotopes of atmospheric CO2 driven by El Nino. Nature. 477:579-582.   10.1038/nature10421   AbstractWebsite

The stable isotope ratios of atmospheric CO2 (O-18/O-16 and C-13/C-12) have been monitored since 1977 to improve our understanding of the global carbon cycle, because biosphere-atmosphere exchange fluxes affect the different atomic masses in a measurable way(1). Interpreting the O-18/O-16 variability has proved difficult, however, because oxygen isotopes in CO2 are influenced by both the carbon cycle and the water cycle(2). Previous attention focused on the decreasing O-18/O-16 ratio in the 1990s, observed by the global Cooperative Air Sampling Network of the US National Oceanic and Atmospheric Administration Earth System Research Laboratory. This decrease was attributed variously to a number of processes including an increase in Northern Hemisphere soil respiration(3); a global increase in C-4 crops at the expense of C-3 forests(4); and environmental conditions, such as atmospheric turbulence(5) and solar radiation(6), that affect CO2 exchange between leaves and the atmosphere. Here we present 30 years' worth of data on O-18/O-16 in CO2 from the Scripps Institution of Oceanography global flask network and show that the interannual variability is strongly related to the El Nino/Southern Oscillation. We suggest that the redistribution of moisture and rainfall in the tropics during an El Nino increases the O-18/O-16 ratio of precipitation and plant water, and that this signal is then passed on to atmospheric CO2 by biosphere-atmosphere gas exchange. We show how the decay time of the El Nino anomaly in this data set can be useful in constraining global gross primary production. Our analysis shows a rapid recovery from El Nino events, implying a shorter cycling time of CO2 with respect to the terrestrial biosphere and oceans than previously estimated. Our analysis suggests that current estimates of global gross primary production, of 120 petagrams of carbon per year(7), may be too low, and that a best guess of 150-175 petagrams of carbon per year better reflects the observed rapid cycling of CO2. Although still tentative, such a revision would present a new benchmark by which to evaluate global biospheric carbon cycling models.

2009
Reid, PC, Fischer AC, Lewis-Brown E, Meredith MP, Sparrow M, Andersson AJ, Antia A, Bates NR, Bathmann U, Beaugrand G, Brix H, Dye S, Edwards M, Furevik T, Gangsto R, Hatun H, Hopcroft RR, Kendall M, Kasten S, Keeling R, Le Quere C, Mackenzie FT, Malin G, Mauritzen C, Olafsson J, Paull C, Rignot E, Shimada K, Vogt M, Wallace C, Wang ZM, Washington R.  2009.  Impacts of the Oceans on Climate Change. Advances in Marine Biology. 56( Sims DW, Ed.).:1-150., San Diego: Elsevier Academic Press Inc   10.1016/s0065-2881(09)56001-4   Abstract

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 (CO(2)), and are estimated to have taken up similar to 40% of anthropogenic-sourced CO(2) 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 CO(2) 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 CO(2) 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 the potent greenhouse gas methane from hydrates and permafrost. The Southern Ocean plays a critical role in driving, modifying and regulating global climate change via the carbon cycle and through its impact on adjacent Antarctica. The Antarctic Peninsula has shown some of the most rapid rises in atmospheric and oceanic temperature in the world, with an associated retreat of the majority of glaciers. Parts of the West Antarctic ice sheet are deflating rapidly, very likely due to a change in the flux of oceanic heat to the undersides of the floating ice shelves. The final section on modelling feedbacks from the ocean to climate change identifies limitations and priorities for model development and associated observations. Considering the importance of the oceans to climate change and our limited understanding of climate-related ocean processes, our ability to measure the changes that are taking place are conspicuously inadequate. The chapter highlights the need for a comprehensive, adequately funded and globally extensive ocean observing system to be implemented and sustained as a high priority. Unless feedbacks from the oceans to climate change are adequately included in climate change models, it is possible that the mitigation actions needed to stabilise CO(2) and limit temperature rise over the next century will be underestimated.