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1. Can we believe in high climate sensitivity?

Author

Annan, J. D. and Hargreaves, J. C.

Subjects
Physics - Atmospheric and Oceanic Physics
Abstract

The climate response to anthropogenic forcing has long been one of the dominant uncertainties in predicting future climate change (Houghton et al, 2001). Many observationally-based estimates of climate sensitivity (S) have been presented in recent years, with most of them assigning significant probability to extremely high sensitivity, such as P(S>6C)>5%. However, closer examination reveals that these estimates are based on a number of implausible implicit assumptions. We explain why these estimates cannot be considered credible and therefore have no place in the decision-making process. In fact, when basic probability theory is applied and reasonable assumptions are made, much greater confidence in a moderate value for S (~2.5C) is easily justified, with S very unlikely to be as high as 4.5C.

Published
2006

2. Climate Evolution Through the Onset and Intensification of Northern Hemisphere Glaciation

Author

McClymont, E. L., primary, Ho, S. L., additional, Ford, H. L., additional, Bailey, I., additional, Berke, M. A., additional, Bolton, C. T., additional, De Schepper, S., additional, Grant, G. R., additional, Groeneveld, J., additional, Inglis, G. N., additional, Karas, C., additional, Patterson, M. O., additional, Swann, G. E. A., additional, Thirumalai, K., additional, White, S. M., additional, Alonso‐Garcia, M., additional, Anand, P., additional, Hoogakker, B. A. A., additional, Littler, K., additional, Petrick, B. F., additional, Risebrobakken, B., additional, Abell, J. T., additional, Crocker, A. J., additional, de Graaf, F., additional, Feakins, S. J., additional, Hargreaves, J. C., additional, Jones, C. L., additional, Markowska, M., additional, Ratnayake, A. S., additional, Stepanek, C., additional, and Tangunan, D., additional

Published
2023
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3. The Influence of Binary Stars on Dwarf Spheroidal Galaxy Kinematics

Author

Hargreaves, J. C., Gilmore, G., and Annan, J. D.

Subjects
Astrophysics
Abstract

We have completed a Monte-Carlo simulation to estimate the effect of binary star orbits on the measured velocity dispersion in dwarf spheroidal galaxies. This paper analyses previous attempts at this calculation, and explains the simulations which were performed with mass, period and ellipticity distributions similar to that measured for the solar neighbourhood. The conclusion is that with functions such as these, the contribution of binary stars to the velocity dispersion is small. The distributions are consistent with the percentage of binaries detected by observations, although this is quite dependent on the measuring errors and on the number of years over which measurements have been taken. For binaries to be making a significant contribution to the dispersion measured in dSph galaxies, the distributions of the orbital parameters would need to be very different from those of stars in the solar neighbourhood. In particular more smaller period orbits with higher mass secondaries would be required. The shape of the velocity distribution may help to resolve this issue when more data becomes available. In general, the scenarios producing a larger apparent dispersion have a velocity distribution which deviates more clearly from Gaussian., Comment: MNRAS in press, uuencoded ps file

Published
1995
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6. Long-Term Climate Commitments Projected with Climate–Carbon Cycle Models

Author

Plattner, G.-K., Knutti, R., Joos, F., Stocker, T. F., von Bloh, W., Brovkin, V., Cameron, D., Driesschaert, E., Dutkiewicz, S., Eby, M., Edwards, N. R., Fichefet, T., Hargreaves, J. C., Jones, C. D., Loutre, M. F., Matthews, H. D., Mouchet, A., Müller, S. A., Nawrath, S., Price, A., Sokolov, A., Strassmann, K. M., and Weaver, A. J.

Published
2008

9. Effects of atmospheric dynamics and ocean resolution on bi-stability of the thermohaline circulation examined using the Grid ENabled Integrated Earth system modelling (GENIE) framework

Author

Lenton, T. M., Marsh, R., Price, A. R., Lunt, D. J., Aksenov, Y., Annan, J. D., Cooper-Chadwick, T., Cox, S. J., Edwards, N. R., Goswami, S., Hargreaves, J. C., Harris, P. P., Jiao, Z., Livina, V. N., Payne, A. J., Rutt, I. C., Shepherd, J. G., Valdes, P. J., Williams, G., Williamson, M. S., and Yool, A.

Published
2007
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10. Large-scale features and evaluation of the PMIP4-CMIP6 midHolocene simulations

Author

Brierley, C. M., Zhao, A., Harrison, S. P., Braconnot, P., Williams, C. J. R., Thornalley, D. J. R., Shi, X., Peterschmitt, J. -Y., Ohgaito, R., Kaufman, D. S., Kageyama, M., Hargreaves, J. C., Erb, M. P., Emile-Geay, J., D'Agostino, R., Chandan, D., Carre, M., Bartlein, P. J., Zheng, W., Zhang, Z., Zhang, Q., Yang, H., Volodin, E. M., Tomas, R. A., Routson, C., Richard Peltier, W., Otto-Bliesner, B., Morozova, P. A., Mckay, N. P., Lohmann, G., Legrande, A. N., Guo, C., Cao, J., Brady, E., Annan, J. D., Abe-Ouchi, A., Department of Geography, University College of London [London] (UCL), Laboratoire des Sciences du Climat et de l'Environnement [Gif-sur-Yvette] (LSCE), Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS), Variabilité à long terme du climat de l'océan (VALCO), Laboratoire d'Océanographie et du Climat : Expérimentations et Approches Numériques (LOCEAN), Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-École normale supérieure - Paris (ENS-PSL), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité)-Muséum national d'Histoire naturelle (MNHN)-Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université Paris Cité (UPCité), Institut national des sciences de l'Univers (INSU - CNRS)-Université Paris-Saclay-Centre National de la Recherche Scientifique (CNRS)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ), Institut Pierre-Simon-Laplace (IPSL (FR_636)), École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-École normale supérieure - Paris (ENS Paris), Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)-Institut Pierre-Simon-Laplace (IPSL (FR_636)), and Université Paris sciences et lettres (PSL)-Université Paris sciences et lettres (PSL)-Université de Versailles Saint-Quentin-en-Yvelines (UVSQ)-Commissariat à l'énergie atomique et aux énergies alternatives (CEA)-Institut national des sciences de l'Univers (INSU - CNRS)-École polytechnique (X)-Centre National d'Études Spatiales [Toulouse] (CNES)-Sorbonne Université (SU)-Centre National de la Recherche Scientifique (CNRS)-Université de Paris (UP)-Institut de Recherche pour le Développement (IRD)-Muséum national d'Histoire naturelle (MNHN)-Centre National de la Recherche Scientifique (CNRS)-Sorbonne Université (SU)

Subjects
PMIP4-CMIP6, purl.org/pe-repo/ocde/ford#1.05.00 [https], midHolocene simulations, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment
Abstract

The mid-Holocene (6,000 years ago) is a standard experiment for the evaluation of the simulated response of global climate models using paleoclimate reconstructions. The latest mid-Holocene simulations are a contribution by the Palaeoclimate Model Intercomparison Project (PMIP4) to the current phase of the Coupled Model Intercomparison Project (CMIP6). Here we provide an initial analysis and evaluation of the results of the experiment for the mid-Holocene. We show that state-of-the-art models produce climate changes that are broadly consistent with theory and observations, including increased summer warming of the northern hemisphere and associated shifts in tropical rainfall. Many features of the PMIP4-CMIP6 simulations were present in the previous generation (PMIP3-CMIP5) of simulations. The PMIP4-CMIP6 ensemble for the mid-Holocene has a global mean temperature change of -0.3 K, which is -0.2 K cooler that the PMIP3-CMIP5 simulations predominantly as a result of the prescription of realistic greenhouse gas concentrations in PMIP4-CMIP6. Neither this difference nor the improvement in model complexity and resolution seems to improve the realism of the simulations. Biases in the magnitude and the sign of regional responses identified in PMIP3-CMIP5, such as the amplification of the northern African monsoon, precipitation changes over Europe and simulated aridity in mid-Eurasia, are still present in the PMIP4-CMIP6 simulations. Despite these issues, PMIP4-CMIP6 and the mid-Holocene provide an opportunity both for quantitative evaluation and derivation of\ud emergent constraints on climate sensitivity and feedback strength.

Published
2020
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11. An assessment of Earth's climate sensitivity using multiple lines of evidence

Author

Sherwood, S., Webb, M. J., Annan, J. D., Armour, K. C., Forster, P. M., Hargreaves, J. C., Hegerl, G., Klein, S. A., Marvel, K. D., Rohling, E. J., Watanabe, Makoto, Andrews, T., Braconnot, Pascale, Bretherton, C. S., Foster, G. L., Hausfather, Z., Heydt, A. S. von der, Knutti, R., Mauritsen, T., Norris, J. R., Proistosescu, C., Rugenstein, M.A.A., Schmidt, G. A., Tokarska, K. B., Zelinka, M. D., Sherwood, S., Webb, M. J., Annan, J. D., Armour, K. C., Forster, P. M., Hargreaves, J. C., Hegerl, G., Klein, S. A., Marvel, K. D., Rohling, E. J., Watanabe, Makoto, Andrews, T., Braconnot, Pascale, Bretherton, C. S., Foster, G. L., Hausfather, Z., Heydt, A. S. von der, Knutti, R., Mauritsen, T., Norris, J. R., Proistosescu, C., Rugenstein, M.A.A., Schmidt, G. A., Tokarska, K. B., and Zelinka, M. D.

Abstract

We assess evidence relevant to Earth's equilibrium climate sensitivity per doubling of atmospheric CO2, characterized by an effective sensitivity S. This evidence includes feedback process understanding, the historical climate record, and the paleoclimate record. An S value lower than 2 K is difficult to reconcile with any of the three lines of evidence. The amount of cooling during the Last Glacial Maximum provides strong evidence against values of S greater than 4.5 K. Other lines of evidence in combination also show that this is relatively unlikely. We use a Bayesian approach to produce a probability density (PDF) for S given all the evidence, including tests of robustness to difficult-to-quantify uncertainties and different priors. The 66% range is 2.6-3.9 K for our Baseline calculation, and remains within 2.3-4.5 K under the robustness tests; corresponding 5-95% ranges are 2.3-4.7 K, bounded by 2.0-5.7 K (although such high-confidence ranges should be regarded more cautiously). This indicates a stronger constraint on S than reported in past assessments, by lifting the low end of the range. This narrowing occurs because the three lines of evidence agree and are judged to be largely independent, and because of greater confidence in understanding feedback processes and in combining evidence. We identify promising avenues for further narrowing the range in S, in particular using comprehensive models and process understanding to address limitations in the traditional forcing-feedback paradigm for interpreting past changes.

Published
2020

12. An Assessment of Earth's Climate Sensitivity Using Multiple Lines of Evidence

Author

Sherwood, S. C., Webb, M. J., Annan, J. D., Armour, K. C., Forster, P. M., Hargreaves, J. C., Hegerl, G., Klein, S. A., Marvel, K. D., Rohling, E. J., Watanabe, M., Andrews, T., Braconnot, P., Bretherton, C. S., Foster, G. L., Hausfather, Z., Heydt, A. S., Knutti, R., Mauritsen, Thorsten, Norris, J. R., Proistosescu, C., Rugenstein, M., Schmidt, G. A., Tokarska, K. B., Zelinka, M. D., Sherwood, S. C., Webb, M. J., Annan, J. D., Armour, K. C., Forster, P. M., Hargreaves, J. C., Hegerl, G., Klein, S. A., Marvel, K. D., Rohling, E. J., Watanabe, M., Andrews, T., Braconnot, P., Bretherton, C. S., Foster, G. L., Hausfather, Z., Heydt, A. S., Knutti, R., Mauritsen, Thorsten, Norris, J. R., Proistosescu, C., Rugenstein, M., Schmidt, G. A., Tokarska, K. B., and Zelinka, M. D.

Abstract

We assess evidence relevant to Earth's equilibrium climate sensitivity per doubling of atmospheric CO2, characterized by an effective sensitivity S. This evidence includes feedback process understanding, the historical climate record, and the paleoclimate record. An S value lower than 2 K is difficult to reconcile with any of the three lines of evidence. The amount of cooling during the Last Glacial Maximum provides strong evidence against values of S greater than 4.5 K. Other lines of evidence in combination also show that this is relatively unlikely. We use a Bayesian approach to produce a probability density function (PDF) for S given all the evidence, including tests of robustness to difficult-to-quantify uncertainties and different priors. The 66% range is 2.6-3.9 K for our Baseline calculation and remains within 2.3-4.5 K under the robustness tests; corresponding 5-95% ranges are 2.3-4.7 K, bounded by 2.0-5.7 K (although such high-confidence ranges should be regarded more cautiously). This indicates a stronger constraint on S than reported in past assessments, by lifting the low end of the range. This narrowing occurs because the three lines of evidence agree and are judged to be largely independent and because of greater confidence in understanding feedback processes and in combining evidence. We identify promising avenues for further narrowing the range in S, in particular using comprehensive models and process understanding to address limitations in the traditional forcing-feedback paradigm for interpreting past changes.

Published
2020
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14. Using Paleo-climate Comparisons to Constrain Future Projections in CMIP5

Author

Schmidt, G. A, Annan, J D, Bartlein, P. J, Cook, B. I, Guilyardi, E, Hargreaves, J. C, Harrison, S. P, Kageyama, M, LeGrande, A. N, Konecky, B, Lovejoy, S, Mann, M. E, Masson-Delmotte, V, Risi, C, Thompson, D, Timmermann, A, Tremblay, L.-B, and Yiou, P

Subjects
Meteorology And Climatology
Abstract

We present a description of the theoretical framework and best practice for using the paleo-climate model component of the Coupled Model Intercomparison Project (Phase 5) (CMIP5) to constrain future projections of climate using the same models. The constraints arise from measures of skill in hindcasting paleo-climate changes from the present over 3 periods: the Last Glacial Maximum (LGM) (21 thousand years before present, ka), the mid-Holocene (MH) (6 ka) and the Last Millennium (LM) (8501850 CE). The skill measures may be used to validate robust patterns of climate change across scenarios or to distinguish between models that have differing outcomes in future scenarios. We find that the multi-model ensemble of paleo-simulations is adequate for addressing at least some of these issues. For example, selected benchmarks for the LGM and MH are correlated to the rank of future projections of precipitationtemperature or sea ice extent to indicate that models that produce the best agreement with paleoclimate information give demonstrably different future results than the rest of the models. We also find that some comparisons, for instance associated with model variability, are strongly dependent on uncertain forcing timeseries, or show time dependent behaviour, making direct inferences for the future problematic. Overall, we demonstrate that there is a strong potential for the paleo-climate simulations to help inform the future projections and urge all the modeling groups to complete this subset of the CMIP5 runs.

Published
2013
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15. An Assessment of Earth's Climate Sensitivity Using Multiple Lines of Evidence

Author

Sherwood, S. C., primary, Webb, M. J., additional, Annan, J. D., additional, Armour, K. C., additional, Forster, P. M., additional, Hargreaves, J. C., additional, Hegerl, G., additional, Klein, S. A., additional, Marvel, K. D., additional, Rohling, E. J., additional, Watanabe, M., additional, Andrews, T., additional, Braconnot, P., additional, Bretherton, C. S., additional, Foster, G. L., additional, Hausfather, Z., additional, von der Heydt, A. S., additional, Knutti, R., additional, Mauritsen, T., additional, Norris, J. R., additional, Proistosescu, C., additional, Rugenstein, M., additional, Schmidt, G. A., additional, Tokarska, K. B., additional, and Zelinka, M. D., additional

Published
2020
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18. Sources of multi-decadal variability in Arctic sea ice extent

Author

Day, J. J., Hargreaves, J C, Annan, J D, and Abe-Ouchi, A

Abstract

The observed dramatic decrease in September sea ice extent (SIE) has been widely discussed in the scientific literature. Though there is qualitative agreement between observations and ensemble members of the Third Coupled Model Intercomparison Project (CMIP3), it is concerning that the observed trend (1979–2010) is not captured by any ensemble member. The potential sources of this discrepancy include: observational uncertainty, physical model limitations and vigorous natural climate variability. The latter has received less attention and is difficult to assess using the relatively short observational sea ice records. In this study multi-centennial pre-industrial control simulations with five CMIP3 climate models are used\ud to investigate the role that the Arctic oscillation (AO), the Atlantic multi-decadal oscillation (AMO) and the Atlantic meridional overturning circulation (AMOC) play in decadal sea ice variability. Further, we use the models to determine the impact that these sources of variability\ud have had on SIE over both the era of satellite observation (1979–2010) and an extended observational record (1953–2010). There is little evidence of a relationship between the AO and SIE in the models. However, we find that both the AMO and AMOC indices are significantly correlated with SIE in all the models considered. Using sensitivity statistics derived from the models, assuming a linear relationship, we attribute 0.5–3.1%/decade of the 10.1%/decade decline in September SIE (1979–2010) to AMO driven variability.

Published
2012

19. Assessing the potential long-term increase of oceanic fossil fuel CO2 uptake due to CO2-calcification feedback

Author

Ridgwell , A., Zondervan , I., Hargreaves , J. C., Bijma , J., Lenton , T. M., School of Geographical Sciences, University of Bristol [Bristol], Biogéosciences [Dijon] ( BGS ), Université de Bourgogne ( UB ) -AgroSup Dijon - Institut National Supérieur des Sciences Agronomiques, de l'Alimentation et de l'Environnement-Centre National de la Recherche Scientifique ( CNRS ), Frontier Research Center for Global Change ( FRCGC ), Japan Agency for Marine-Earth Science and Technology ( JAMSTEC ), School of Environmental Sciences [Norwich], University of East Anglia [Norwich] ( UEA ), and EGU, Publication

Subjects
[ SDU.OCEAN ] Sciences of the Universe [physics]/Ocean, Atmosphere, [SDU.OCEAN] Sciences of the Universe [physics]/Ocean, Atmosphere, lcsh:QE1-996.5, fungi, lcsh:Life, [ SDU.STU ] Sciences of the Universe [physics]/Earth Sciences, [SDU.ASTR] Sciences of the Universe [physics]/Astrophysics [astro-ph], [ PHYS.ASTR.CO ] Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], [SDU.ENVI] Sciences of the Universe [physics]/Continental interfaces, environment, lcsh:Geology, lcsh:QH501-531, [PHYS.ASTR.CO] Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], lcsh:QH540-549.5, [SDU.STU] Sciences of the Universe [physics]/Earth Sciences, [ SDU.ENVI ] Sciences of the Universe [physics]/Continental interfaces, environment, lcsh:Ecology, [ SDU.ASTR ] Sciences of the Universe [physics]/Astrophysics [astro-ph]
Abstract

International audience; Plankton manipulation experiments exhibit a wide range of sensitivities of biogenic calcification to simulated anthropogenic acidification of the ocean, with the "lab rat" of planktic calcifiers, Emiliania huxleyi apparently not representative of calcification generally. We assess the implications of this observational uncertainty by creating an ensemble of realizations of an Earth system model that encapsulates a comparable range of uncertainty in calcification response to ocean acidification. We predict that a substantial reduction in marine carbonate production is possible in the future, with enhanced ocean CO2 sequestration across the model ensemble driving a 4?13% reduction in the year 3000 atmospheric fossil fuel CO2 burden. Concurrent changes in ocean circulation and surface temperatures in the model contribute about one third to the increase in CO2 uptake. We find that uncertainty in the predicted strength of CO2-calcification feedback seems to be dominated by the assumption as to which species of calcifier contribute most to carbonate production in the open ocean.

Published
2007

20. Significant long-term increase of fossil fuel CO2 uptake from reduced marine calcification

Author

Ridgwell , A., Zondervan , I., Hargreaves , J. C., Bijma , J., Lenton , T. M., EGU, Publication, Department of Earth and Ocean Sciences [Vancouver] (EOS), University of British Columbia (UBC), Biogéosciences [UMR 6282] [Dijon] (BGS), Université de Bourgogne (UB)-AgroSup Dijon - Institut National Supérieur des Sciences Agronomiques, de l'Alimentation et de l'Environnement-Centre National de la Recherche Scientifique (CNRS), Frontier Research Center for Global Change (FRCGC), Japan Agency for Marine-Earth Science and Technology (JAMSTEC), School of Environmental Sciences [Norwich], University of East Anglia [Norwich] (UEA), Department of Earth and Ocean Sciences [Vancouver] ( EOS ), University of British Columbia ( UBC ), Biogéosciences [Dijon] ( BGS ), Université de Bourgogne ( UB ) -AgroSup Dijon - Institut National Supérieur des Sciences Agronomiques, de l'Alimentation et de l'Environnement-Centre National de la Recherche Scientifique ( CNRS ), Frontier Research Center for Global Change ( FRCGC ), Japan Agency for Marine-Earth Science and Technology ( JAMSTEC ), and University of East Anglia [Norwich] ( UEA )

Subjects
[ SDU.OCEAN ] Sciences of the Universe [physics]/Ocean, Atmosphere, [SDU.OCEAN]Sciences of the Universe [physics]/Ocean, Atmosphere, [SDU.ASTR]Sciences of the Universe [physics]/Astrophysics [astro-ph], [SDU.OCEAN] Sciences of the Universe [physics]/Ocean, Atmosphere, fungi, [SDU.STU]Sciences of the Universe [physics]/Earth Sciences, [ SDU.STU ] Sciences of the Universe [physics]/Earth Sciences, [ PHYS.ASTR.CO ] Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], [SDU.ASTR] Sciences of the Universe [physics]/Astrophysics [astro-ph], [SDU.ENVI] Sciences of the Universe [physics]/Continental interfaces, environment, [PHYS.ASTR.CO]Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], [PHYS.ASTR.CO] Physics [physics]/Astrophysics [astro-ph]/Cosmology and Extra-Galactic Astrophysics [astro-ph.CO], [ SDU.ENVI ] Sciences of the Universe [physics]/Continental interfaces, environment, [SDU.STU] Sciences of the Universe [physics]/Earth Sciences, [SDU.ENVI]Sciences of the Universe [physics]/Continental interfaces, environment, [ SDU.ASTR ] Sciences of the Universe [physics]/Astrophysics [astro-ph]
Abstract

International audience; Analysis of available plankton manipulation experiments demonstrates a previously unrecognized wide range of sensitivities of biogenic calcification to simulated anthropogenic acidification of the ocean, with the "lab rat" of planktic calcifiers, Emiliania huxleyi not representative of calcification generally. We assess the implications of the experimental uncertainty in plankton calcification response by creating an ensemble of realizations of an Earth system model that encapsulates a comparable range of uncertainty in calcification response. We predict a substantial future reduction in marine carbonate production, with ocean CO2 sequestration across the model ensemble enhanced by between 62 and 199 PgC by the year 3000, equivalent to a reduction in the atmospheric fossil fuel CO2 burden at that time of up to 13%. Concurrent changes in ocean circulation and surface temperatures contribute about one third to the overall importance of reduced plankton calcification.

Published
2006

22. Using palaeo-climate comparisons to constrain future projections in CMIP5

Author

Schmidt, G. A., primary, Annan, J. D., additional, Bartlein, P. J., additional, Cook, B. I., additional, Guilyardi, E., additional, Hargreaves, J. C., additional, Harrison, S. P., additional, Kageyama, M., additional, LeGrande, A. N., additional, Konecky, B., additional, Lovejoy, S., additional, Mann, M. E., additional, Masson-Delmotte, V., additional, Risi, C., additional, Thompson, D., additional, Timmermann, A., additional, Tremblay, L.-B., additional, and Yiou, P., additional

Published
2014
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26. Using paleo-climate comparisons to constrain future projections in CMIP5

Author

Schmidt, G. A., primary, Annan, J. D., additional, Bartlein, P. J., additional, Cook, B. I., additional, Guilyardi, E., additional, Hargreaves, J. C., additional, Harrison, S. P., additional, Kageyama, M., additional, LeGrande, A. N., additional, Konecky, B., additional, Lovejoy, S., additional, Mann, M. E., additional, Masson-Delmotte, V., additional, Risi, C., additional, Thompson, D., additional, Timmermann, A., additional, Tremblay, L.-B., additional, and Yiou, P., additional

Published
2013
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44. Temporal fine structure of nightime spike events in auroral radio absorption, studied by wavelet method

Author

Hargreaves, John K., Ranta, A., Annan, J. D., Hargreaves, J. C., Hargreaves, John K., Ranta, A., Annan, J. D., and Hargreaves, J. C.

Abstract

The auroral absorption spike event, occurring generally at the onset of a substorm, is distinguished by its high intensity and short duration. This paper reports the presence of a fine structure within the spike event. Analysis of selected examples using the Morlet wavelet shows that within the 1 – 2 min duration of the spike are significant modulations with periodicities in the bands 15 – 60 s (67 – 16 mHz), and 5 – 10 s (200 – 100 mHz), the former being the stronger. The slower fluctuations can amount to more than 10% of the absorption, and they were observed in every example (seven out of nine) in which the spike was moving poleward. They were absent in the other two cases, when the spike moved equatorward. In the examples studied, the 15 – 60 s absorption pulsations were accompanied by magnetic micropulsations of impulsive type (Pi) having a periodity that was similar or harmonically related. The connection is only close while the spike event is moving. Consideration of the details suggests that both the magnetic and the absorption pulsations are related to the acceleration process at substorm onset, the flux of energetic particles into the auroral zone producing the radio absorption being modulated with, though not by, the geomagnetic field variations. The 5 – 10 s pulsations, which are considerably weaker, appeared in both the absorption and the magnetic records, but in this case with no obvious connection between them.

Published
2001

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