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Some recent compilations of proxy data both on land and ocean (MARGO Project Members, 2009; Bartlein et al., 2011; Shakun et al., 2012), have provided a new opportunity for an improved assessment of the overall climatic state of the Last Glacial Maximum. In this paper, we combine these proxy data with the ensemble of structurally diverse state of the art climate models which participated in the PMIP2 project (Braconnot et al., 2007) to generate a spatially complete reconstruction of surface air (and sea surface) temperatures. We test a variety of approaches, and show that multiple linear regression performs well for this application. Our reconstruction is significantly different to and more accurate than previous approaches and we obtain an estimated global mean cooling of 4.0±0.8 °C (95% CI). [ABSTRACT FROM AUTHOR]

Paleoclimate simulations provide us with an opportunity to critically confront and evaluate the performance of climate models in simulating the response of the climate system to changes in radiative forcing and other boundary conditions. Hargreaves et al. (2011) analyzed the reliability of the PMIP2 model ensemble with respect to the MARGO sea surface temperature data synthesis (MARGO Project Members, 2009) for the Last Glacial Maximum (LGM). Here we extend that work to include a new comprehensive collection of land surface data (Bartlein et al., 2011), and introduce a novel analysis of the predictive skill of the models. We include output from the PMIP3 experiments, from the two models for which suitable data are currently available. We also perform the same analyses for the PMIP2 mid-Holocene ensembles and available proxy data sets. Our results are predominantly positive for the LGM, suggesting that as well as the global mean change, the models can reproduce the observed pattern of change on the broadest scales, such as the overall land-sea contrast and polar amplification, although the more detailed regional scale patterns of change remains elusive. In contrast, our results for the mid-Holocene are substantially negative, with the models failing to reproduce the observed changes with any degree of skill. One likely cause of this problem may be that the globally- and annually-averaged forcing anomaly is very weak at the mid-Holocene, and so the results are dominated by the more localized regional patterns. The root cause of the model-data mismatch at regional scales is unclear. If the proxy calibration is itself reliable, then representation error in the data-model comparison, and missing climate feedbacks in the models are other possible sources of error. [ABSTRACT FROM AUTHOR]

The Last Interglaciation (~ 130-115 thousand years ago) was a time when the Arctic climate was warmer than today (Anderson et al., 2006; Kaspar et al., 2005) and sea level extremely likely at least 6 m higher (Kopp et al., 2009). However, there is large uncertainty in the relative contributions to this sea-level rise from the Greenland and Antarctic ice sheets and smaller icefields (Otto-Bliesner et al., 2006; Huybrechts, 2002; Letréguilly et al., 1991; Ritz et al., 1997; Cuffey and Marshall, 2000; Tarasov and Peltier, 2003; Lhomme et al., 2005; Greve, 2005; Robinson et al., 2011; Fyke et al., 2011). By performing an ensemble of 500 coupled climate -- ice sheet model simulations, constrained by paleo-data, we determine probabilistically the likely contribution of Greenland ice sheet melt to Last Interglacial sea-level rise, taking into account model uncertainty. Here we show a 90% probability that Greenland ice melt contributed at least 0.6 m but less than 10% probability it exceeded 3.5 m, a value which is lower than several recent estimates (Cuffey and Marshall, 2000; Tarasov and Peltier, 2003; Lhomme et al., 2005; Robinson et al., 2011). Our combined modeling and paleo-data approach suggests that the Greenland ice sheet is less sensitive to orbital forcing than previously thought, and implicates Antarctic melt as providing a substantial contribution to Last Interglacial sea-level rise. [ABSTRACT FROM AUTHOR]

Henriksson et al. (2010), hereafter HALTL10, criticise Annan and Hargreaves (2006a) (AH06) primarily on the grounds that we assumed that different sources of data were conditionally independent given the climate sensitivity. While we consider this approximation to have been a reasonable one in the circumstances (and provided arguments to justify this approach), we also acknowledged its importance in our original paper and performed several sensitivity analyses. The alternative calculations presented by HALTL10 appear to strengthen rather than contradict our conclusion. HALTL10 additionally criticise Annan and Hargreaves (2009) (AH09) for proposing a Cauchy-type prior (as an alternative to the use of a uniform prior which was widespread up to that time) "without sufficient support", and further claim that our choice was irrationally based on an economic assessment. We are surprised by these baseless claims, especially considering that the proposed prior was justified at some length both on the basis of both the "Charney report" (National Research Council, 1979) and basic physical arguments, and also in light of our elementary demonstration of the pathological failings of the most commonly-used alternative. Thus, these claims are factually incorrect. [ABSTRACT FROM AUTHOR]

Three levels of municipal solid waste compost (MSWC) and two application rates of compost tea made with MSWC were applied to strawberries for two years. The highest Level of application of MSWC significantly increased the concentrations of most extractable soil mineral elements except for Ni which was increased in the highest compost tea application rate. Despite large differences in soil mineral element concentrations among treatments, plant and fruit uptake were generally unaffected by treatments. Notably however, compost tea applications increased fruit Na levels perhaps due to increased uptake of Na by leaves compared to roots. Generally, the composts and compost teas produced fruit of equal quality in terms of total antioxidant capacity and vitamin C but all treatments failed to provide sufficient N to strawberry plants and all fruit appeared to have leather rot; consequently, yield was decreased. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

We have extended the GEN1E-I Earth system model to include a representation of sedimentary stratigraphy and the preservation of biogenic carbonates delivered to the ocean floor. This has enabled us to take a novel approach in diagnosing modem marine carbon cycling: assimilating observation of the calcium carbonate (CaCO3) content of deep-sea sediments with an ensemble Kalman filter. The resulting calibrated model predicts a mean surface sediment content (32.5 wt%) close to the observed value (34.8 wt%), and a global burial rate of CaCO3 in deep sea sediments of 0.121 PgC yr-1, in line with recent budget estimates of 0.10–0.14 PgC yr-1. We employ the GENIE-1 model in quantifying the multimillennial-scale fate of fossil fuel CO2 emitted to the atmosphere. In the absence of any interaction between ocean and sediments, an equilibrium partitioning of CO2 is reached within ∼1000 years of emissions ceasing, with 34% (645 ppm) remaining in the atmosphere out of a total fossil fuel bum of 4173 PgC. An additional 12% of CO2 emissions (223 ppm) are sequestered as bicarbonate ions (HCO3-) by reaction with deep-sea carbonates (‘seafloor CaCO3 neutralization’) on a timescale of ∼1.7 ka. Excess of carbonate weathering on land over deep-sea burial results in a further net transformation of 14% of CO2 emissions (261 ppm) into HCO3- (‘terrestrial CaCO3 neutralization’) on a timescale of ∼8.3 ka. We have also assessed the importance of a changing climate in modulating the stabilization of atmospheric CO2 through ocean-sediment interaction. Increased ocean stratification suppresses particulate organic carbon export, which in turn enhances seafloor CaCO3 preservation. The resulting reduction in the sequestration of fossil fuel CO2 represents a new positive feedback on millennial-scale climate change. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

This paper describes the development and application of a technique for using satellite altimeter measurements as boundary data to drive the nearshore spectral wave model, SWAN. The aim was to assess the impact in coastal areas of extreme events or changes in offshore climatology and to extend the usefulness of satellite altimetry further inshore. For the purpose of verifying the technique, three test areas where both bathymetry and some in situ data were available were chosen. The technique could, potentially, be applied to any coastal location where there is bathymetric information although, as the results reported in this paper show, intelligence must be used in adapting the methodology for different sites. It is also necessary to have information on the local wind field from either models or measurements. The experiments at the three test areas demonstrated that there is not a simple relationship between the offshore wave height climate and the inshore climate in a particular region. Important complicating factors are bathymetry, tidal range and incident wave angle. As was most clearly demonstrated in the Carmarthen Bay test area, bathymetric complexity leads to high spatial variation in the amount of wave energy dissipated close to the coast. In the study of extreme wave events described in this paper the exact value of the local wind field was not found to be critical. This work was a first trial combining wave climatology derived from satellite altimetry with a third generation coastal wave model so was necessarily experimental. The general trends and patterns of spatial variation obtained are encouraging but there remains significant, unquantifiable uncertainty in the results. Better observations of nearshore waves, improved understanding of the joint probability distribution of water level and waves as well as more knowledge of future climate change would all improve accuracy. [ABSTRACT FROM AUTHOR]