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The incorporation of diffusive and convective processes into symmetry methods for determination of the effect of time-dependent forcing on oceanic basic-scale flows provides a realistic steady solution. The numerical solutions of the ideal thermocline equations show that the oscillations cause changes in the heat fluxes and time-averaged mass of the steady state solution. Symmetry of the time-dependent thermocline equation gives wave-like solutions using arbitrary steady solutions. The steady solution can be useful in annual fluctuations in thermocline depth.

The benefits of implementing negative emission technologies for a century (years 2070-2170) on the global warming response to cumulative carbon emissions until year 2420 are assessed with a comprehensive set of intermediate complexity Earth system model integrations. Model integrations include 82 different model realisations covering a wide range of plausible climate states. The global warming response is assessed in terms of two key climate metrics: the effective transient climate response to cumulative CO2 emissions (eTCRE), measuring the surface warming response to cumulative carbon emissions and associated non-CO2 (RCP4.5) forcing, and the zero emissions commitment (ZEC), measuring the extent of any continued warming after net zero is reached. The TCRE is approximated from eTCRE by removing the contributions of non-CO2 forcing as 2.15 °C EgC-1 (with a 10-90 % range of 1.6 to 2.8 °C EgC-1). During the net positive emission phases, the eTCRE decreases from 2.62 (1.90 to 3.65) to 2.30 (1.73 to 3.23) °C EgC-1 due to a weakening in the increase in radiative forcing with an increase in atmospheric carbon, which is partly opposed by an increasing fraction of the radiative forcing warming the surface as the ocean stratifies. During the negative and zero emission phases, a progressive reduction of the eTCRE to 2.0 (1.4 to 2.8) °C EgC-1 is driven by the reducing airborne fraction as CO2 is drawn down by the ocean. The model uncertainty in the slopes of warming versus cumulative CO2 emissions varies from being controlled by the radiative feedback parameter during positive emissions to also being affected by ocean circulation and carbon-cycle parameters during zero or net-negative emissions. There is hysteresis in atmospheric CO[sub 2] and surface warming, where atmospheric CO2 and surface temperature are higher after peak emissions compared with before peak emissions. The continued warming after emissions cease defining the ZEC for the model mean without carbon capture is -0.01 °C at 25 years and decreases in time to -0.15 °C at 90 years after emissions cease. However, there is a spread in the ensemble with a temperature overshoot occurring in 50 % of the ensemble members at year 25. The ZEC only becomes negative in all ensemble members if modest carbon capture is included. Hence, incorporating negative emissions enhances the ability to meet climate targets and avoid risk of continued warming after net zero is reached. [ABSTRACT FROM AUTHOR]

This article reports the results of a collaborative effort to estimate agricultural productivities in past societies using Seshat: Global History Databank. We focus on 30 Natural Geographic Areas (NGAs) distributed over 10 major world regions (Europe, Africa, Southwest Asia, South Asia, Southeast Asia, East Asia, Central Eurasia, North America, South America, and Oceania). The conceptual framework that we use to obtain these estimates combines the influences of the production technologies (and how they change with time), climate change, and effects of artificial selection into a Relative Yield Coefficient, indicating how agricultural productivity changed over time in each NGA between the Neolithic and the 20th century. We then use estimates of historical yield in each NGA to translate the Relative Yield Coefficient into an Estimated Yield (tonnes per hectare per year) trajectory. We tested the proposed methodology in two ways. For eight NGAs, in which we had more than one historical yield estimate, we used the earliest estimate to anchor the trajectory and compared the ensuing trajectory to the remaining estimates. We also compared the end points of the estimated NGA trajectories to the earliest (the 1960s decade) FAO data on crop productivities in the modern countries encompassing Seshat NGAs. We discuss the benefits of this methodology over previous efforts to estimate agricultural productivities in world history. [ABSTRACT FROM AUTHOR]

An idealized, two-dimensional, numerical investigation of the nonlinear development of instabilities, focusing almost exclusively on the double-diffusive case is described. Nonlinearity arising from changes in diffusive regime is found to be more important than advective nonlinearity in promoting global equilibration.

The Water-Energy-Food Nexus approach to the governance of natural resources seeks to identify and address the synergies and trade-offs amongst traditionally separated sectors, to capture significant feedbacks that have so far remained insufficiently understood and regulated. One key specificity of the Nexus approach is the need for intersectoral, cross-scale and stakeholder integration, which is particularly challenging due to the lack of policy coordination prevailing in many countries. Yet, some emerging integrated policy processes, such as those aimed at implementing nationally determined contributions (NDCs) under the 2015 Paris Agreement, may offer a sufficient level of integration to mainstream the Nexus approach. This article focuses on the potential of such NDC processes in Brazil. NDC processes in China, the European Union, India and Mexico are used as indicators associated with higher or lower degrees of integration for a more specific analysis of the case of Brazil. The article concludes that the barriers to sectoral integration raised by the dominant position of the agricultural sector in Brazil as regards, among other things, environmental legislation, are unlikely to be overcome by internal action. This represents a threat to achieving the target of zero deforestation in Brazil, considering the cropland-livestock forestry feedbacks involved in the growing demand for agricultural commodities from China. NDCs already provide space for international cooperation, which could be further developed to include measures for linking demand for agricultural commodities from the EU and China, and massive land-use change and deforestation in Brazil. Key policy insights The NDCs from India, China, EU, Mexico and Brazil recognize, to varying extents, the Nexus approach in their climate policies, particularly the link with water uses in agriculture. The NDCs from EU, Mexico and Brazil include some elaborated Nexus issues related to indirect land use-forestry-agriculture. Sectoral integration could be progressively strengthened under the Nexus approach as part of the five-yearly updates of the NDCs. The NDCs from Brazil and China could provide a policy window to integrate indirect land use-forestry-agriculture collaborative measures, for the purposes of tackling the deforestation trade-off resulting from Brazilian exports of soybeans to China. [ABSTRACT FROM AUTHOR]

The concentration of CO2 in the atmosphere is sensitive to changes in the depth at which sinking particulate organic matter is remineralised: often described as a change in the exponent "b" of the Martin curve. Sediment trap observations from deep and intermediate depths suggest there is a spatially heterogeneous pattern of b, particularly varying with latitude, but disagree over the exact spatial patterns. Here we use a biogeochemical model of the phosphorus cycle coupled with a steady-state representation of ocean circulation to explore the sensitivity of preformed phosphate and atmospheric CO2 to spatial variability in remineralisation depths. A Latin hypercube sampling method is used to simultaneously vary the Martin curve indepedently within 15 different regions, as a basis for a regression-based analysis used to derive a quantitative measure of sensitivity. Approximately 30% of the sensitivity of atmospheric CO2 to changes in remineralisation depths is driven by changes in the Subantarctic region (36° S to 60° S), simliar in magnitude to the Pacific basin despite the much smaller area and lower productivity. Overall, the absolute magnitude of sensitivity is controlled by export production but the relative spatial patterns in sensitivity are predominantly constrained by ocean circulation pathways. The high sensitivity in the Subantarctic regions is driven by a combination of high export production and the high connectivity of these regions to regions important for the export of preformed nutrients such as the Southern Ocean and North Atlantic. Overall, regionally varying remineralisation depths contribute to variability in CO2 of between %5-15 ppm relative to a global mean change in remineralisation depth. Future changes in the environmental and ecological drivers of remineralisation, such as temperature and ocean acidification, are expected to be most significant in the high latitudes where CO2 sensitivity to remineralisation is also highest. The importance of ocean circulation pathways to the high sensitivity in Subantarctic regions also has significance for past climates given the importance of circulation changes in the Southern Ocean. [ABSTRACT FROM AUTHOR]

The early Eocene, from about 56 Ma, with high atmospheric CO2 levels, offers an analogue for the response of the Earth's climate system to anthropogenic fossil fuel burning. In this study, we present an ensemble of 50 Earth system model runs with an early Eocene palaeogeography and variation in the forcing values of atmospheric CO2 and the Earth's orbital parameters. Relationships between simple summary metrics of model outputs and the forcing parameters are identified by linear modelling, providing estimates of the relative magnitudes of the effects of atmospheric CO2 and each of the orbital parameters on important climatic features, including tropical-polar temperature difference, ocean-land temperature contrast, Asian, African and South (S.) American monsoon rains, and climate sensitivity. Our results indicate that although CO2 exerts a dominant control on most of the climatic features examined in this study, the orbital parameters also strongly influence important components of the ocean-atmosphere system in a greenhouse Earth. In our ensemble, atmospheric CO2 spans the range 280-3000 ppm, and this variation accounts for over 90% of the effects on mean air temperature, southern winter high-latitude ocean-land temperature contrast and northern winter tropical-polar temperature difference. However, the variation of precession accounts for over 80% of the influence of the forcing parameters on the Asian and African monsoon rainfall, and obliquity variation accounts for over 65% of the effects on winter ocean-land temperature contrast in high northern latitudes and northern summer tropical-polar temperature difference. Our results indicate a bimodal climate sensitivity, with values of 4.36 and 2.54 °C, dependent on low or high states of atmospheric CO2 concentration, respectively, with a threshold at approximately 1000 ppm in this model, and due to a saturated vegetation-albedo feedback. Our method gives a quantitative ranking of the influence of each of the forcing parameters on key climatic model outputs, with additional spatial information from singular value decomposition providing insights into likely physical mechanisms. The results demonstrate the importance of orbital variation as an agent of change in climates of the past, and we demonstrate that emulators derived from our modelling output can be used as rapid and efficient surrogates of the full complexity model to provide estimates of climate conditions from any set of forcing parameters. [ABSTRACT FROM AUTHOR]

The research described in this paper is undertaken under the banner of the smart city, a concept that captures the way urban spaces are re-made by the incursion of new technology. Much of smart is centred on converting everyday activities into data, and using this data to generate knowledge mediated by technology. Ordinary citizens, those that may have their lives impacted by the technology, usually are not properly involved in the 'smartification' process. Their perceptions, concerns and expectations should inform the conception and development of smart technologies at the same extent. How to engage general public with smart cities research is the central challenge for the Making Metrics Meaningful (MMM) project. Applying a rapid participatory method, 'Imagine' over a five-month period (March - July) the research sought to gain insights from the general public into novel forms of information system innovation. This brief paper describes the nature of the accelerated research undertaken and explores some of the themes which emerged in the analysis. Generic themes, beyond the remit of an explicit transport focus, are developed and pointers towards further research directions are discussed. Participatory methods, including engaging with self-selected transport users actively through both picture creation and programmatically specific musical 'signatures' as well as group discussion, were found to be effective in eliciting users' own concerns, needs and ideas for novel information systems. [ABSTRACT FROM AUTHOR]

During the Last Glacial Maximum (LGM), atmospheric CO2 was around 90 ppmv lower than during the preindustrial period. Despite years of research, however, the exact mechanisms leading to the glacial atmospheric CO2 drop are still not entirely understood. Here, a large (471-member) ensemble of GENIE-1 simulations is used to simulate the equilibrium LGM minus preindustrial atmospheric CO2 concentration difference (ΔCO2). The ensemble has previously been weakly constrained with modern observations and was designed to allow for a wide range of large-scale feedback response strengths. Out of the 471 simulations, 315 complete without evidence of numerical instability, and with a ΔCO2 that centres around -20 ppmv. Roughly a quarter of the 315 runs predict a more significant atmospheric CO2 drop, between ~ 30 and 90 ppmv. This range captures the error in the model's process representations and the impact of processes which may be important for ΔCO2 but are not included in the model. These runs jointly constitute what we refer to as the plausible glacial atmospheric CO2 change-filtered (PGACF) ensemble. Our analyses suggest that decreasing LGM atmospheric CO2 tends to be associated with decreasing SSTs, increasing sea ice area, a weakening of the Atlantic Meridional Overturning Circulation (AMOC), a strengthening of the Antarctic Bottom Water (AABW) cell in the Atlantic Ocean, a decreasing ocean biological productivity, an increasing CaCO3 weathering flux, an increasing terrestrial biosphere carbon inventory and an increasing deep-sea CaCO3 burial flux. The increases in terrestrial biosphere carbon are predominantly due to our choice to preserve rather than destroy carbon in ice sheet areas. However, the ensemble soil respiration also tends to decrease significantly more than net photosynthesis, resulting in relatively large increases in non-burial carbon. In a majority of simulations, the terrestrial biosphere carbon increases are also accompanied by decreases in ocean carbon and increases in lithospheric carbon. In total, however, we find there are 5 different ways of achieving a plausible ΔCO2 in terms of the sign of individual carbon reservoir changes. The PGACF ensemble members also predict both positive and negative changes in global particulate organic carbon (POC) flux, AMOC and AABW cell strengths, and global CaCO3 burial flux. Comparison of the PGACF ensemble results against observations suggests that the simulated LGM physical climate and biogeochemical changes are mostly of the right sign and magnitude or within the range of observational error, except for the change in global deep-sea CaCO3 burial flux - which tends to be overestimated. We note that changing CaCO3 weathering flux is a variable parameter (included to account for variation in both the CaCO3 weathering rate and the un-modelled CaCO3 shallow water deposition flux), and this parameter is strongly associated with changes in global CaCO3 burial rate. The increasing terrestrial carbon inventory is also likely to have contributed to the LGM increase in deep-sea CaCO3 burial flux via the process of carbonate compensation. However, we do not yet rule out either of these processes as causes of ΔCO2 since missing processes such as Si fertilisation, Si leakage and the effect of decreasing SSTs on CaCO3 production may have introduced a high LGM global CaCO3 burial rate bias. Including these processes would, all else held constant, lower the rain ratio seen by the sediments and result in a decrease in atmospheric CO2 and increase in ocean carbon. Despite not modelling Δ14C(atm (DIC)) and δ13C(atm (DIC)), we also highlight some ways in which our results may potentially be reconciled with these records. [ABSTRACT FROM AUTHOR]

The early Eocene, from about 56 Ma, with high atmospheric CO2 levels, offers an analogue for the response of the Earth's climate system to anthropogenic fossil fuel burning. In this study we present an ensemble of 50 Earth system model runs with an early Eocene palaeogeography and variation in the forcing values of atmospheric CO2 and the Earth's orbital parameters. Two-dimensional model output fields are reduced to scalar values through simple summarising algorithms and by singular value decomposition. Relationships between these scalar results and the forcing parameters are identified by linear modelling, providing estimates of the relative magnitudes of the effects of atmospheric CO2 and each of the orbital parameters on important climatic features, including tropical-polar temperature difference, ocean-land temperature contrast, and Asian, African and S. American monsoon rains. Our results indicate that although CO2 exerts a dominant control on most of the climatic features examined in this study, the orbital parameters also strongly influence important components of the ocean-atmosphere system in a greenhouse Earth. In our ensemble, atmospheric CO2 spans the range 280-3000 ppm, and this variation accounts for over 95 % of the effects on mean air temperature, southern winter high-latitude ocean-land temperature contrast and northern winter tropical-polar temperature difference. However, the variation of precession accounts for over 75 % of the influence of the forcing parameters on the Asian and African monsoon rainfall, and obliquity variation accounts for over 65 % of the effects on winter ocean-land temperature contrast in high northern latitudes. Our method gives a quantitative ranking of the influence of each of the forcing parameters on key climatic model outputs, with additional spatial information from our singular value decomposition approach providing insights into likely physical mechanisms. The results demonstrate the importance of orbital variation as an agent of change in climates of the past. [ABSTRACT FROM AUTHOR]