Stable boundary layers: Observations,models and variability part I: Modelling and measurements

Selected field measurements of evening stable boundary layers are presented in detail comparable with published Large Eddy Simulation results. Such models appear to match idealized theories more closely than do some boundary-layer observations. Any attempt to compare detailed observations with idealized models therefore highlights the variability of the real boundary layer.Here direct turbulence measurements across the stable boundary layer from a heterogeneous and an ideal site are contrasted. Recommendations are made for the information needed to distinguish heterogeneous and ideal cases.The companion paper (Part II) discusses further the issues of data, analysis in the presence of variability, and the effects of averaging over heterogeneous terrain.Part of UK Meteorological Office Atmospheric Process Research Division.     

Climate-smart agriculture: perspectives and framings

This paper offers a systematic analysis of the concepts and contexts that frame the climate-smart agriculture (CSA) discourse in the academic and policy literature. Documents (n?=?113) related to CSA and published in peer-reviewed journals, books, working papers, and scientific reports from 2004 to 2016 were reviewed. Three key trends emerged from the analysis: studies are biased towards global policy agendas; research focuses on scientific and technical issues; and the integration of mitigation, adaptation, and food security (the three pillars of CSA) is becoming a popular scholarly solution. Findings suggest that CSA is a fairly new concept used to describe a range of adaptation and mitigation practices without a specific set of criteria. Although CSA is often framed around the three pillars, the underlying issues constructing the discourse differ at global, developing, and developed country scales. Although there is increasing research on developing countries, particularly in relation to how CSA can transform smallholder agriculture, there is a paucity of research documenting the experiences from developed countries. The findings suggest that research on CSA needs to move beyond solely focussing on scientific approaches and only in certain geographical contexts. If CSA is to be applicable for farmers across the globe, then cross-disciplinary research that is underpinned by broad socio-economic and political contexts is essential to understand how differences in narratives might affect implementation on-the-ground in both developing and developed countries.

POLICY RELEVANCE

Although policy makers are increasingly supportive of the climate-smart agriculture (CSA) approach, the rhetoric has largely been developed on the basis of scientific and technical arguments. The political implications of varying perspectives have resulted in a growing divide between how developing and developed countries frame solutions to the impacts of climate change on agriculture under the 2015 Paris Agreement. Different framings are part of the explanation for why the scope of CSA is being rethought, with the scientific community redirecting attention to seeking a separate work programme under the United Nations Framework Convention on Climate Change (UNFCCC). The current policy framing of CSA will give no new policy direction unless it grounds itself in the smallholder farmer and civil society contexts.     

Soil Carbon: Policy and Economics

Agricultural soils provide a prospective way of mitigating the increasing atmospheric concentration of CO₂. A number of agricultural practices are known to stimulate the accumulation of additional soil carbon and early indications are that some might sequester carbon at relatively modest costs with generally positive environmental effects. We discuss, under 10 themes, policy and economic issues that will determine whether programs for sequestration of carbon in agricultural soils can succeed. The issues involve contexts for implementation, economics, private property rights, agricultural policy, and institutional and social structures. Ultimately, success will depend on the incentive structure developed and the way in which carbon sequestration is integrated into the total fabric of agricultural policy.     

Lightning and climate: A review

Research on regional and global lightning activity and the global electrical circuit is summarized. This area of activity has greatly expanded through observations of lightning by satellite and through increased use of the natural (Schumann) resonances of the Earth–ionosphere cavity. The global electrical circuit provides a natural framework for monitoring global change on many time scales. Lightning is responsive to temperature on many time scales, but the sensitivity to temperature appears to diminish at the longer time scales.     

区间系统与区间优化模型——理论与应用

区间系统与区间优化模型是一种应用广泛的描述不确定性问题的数学模型.本文综述区间系统与区间优化模型在理论与应用方面的研究进展.特别地,本文将介绍区间线性系统的解和可解性问题、区间线性优化模型的最优解和最优性问题以及区间二次优化模型的最优解和最优性问题,最后简单概述它们的各种应用实例.     

Climate Change and Agricultural Soils: Impacts and Adaptation

This article reviews the current state of knowledge on the response of soils to climate change, and the implications such changes have for agriculture. The article is based on the material reported in the IPCC second assessment report (Watson et al., 1996) and updated with more recent information, where appropriate. The review highlights the importance of understanding the dynamics of soil processes when addressing climate change impacts on agriculture. Rapid soil responses to climate change (e.g. soil water, organic carbon and erodibility) have been widely investigated and reported in the literature. However, it is important that longer-term processes (e.g. pedogenesis) are not ignored by the research community because these have potentially important implications for long-term agricultural land use and are often irreversible. The use of good land management practices, as currently understood, provides the best strategy for adaptation to the impact of climate change on soils. However, it appears likely that farmers will need to carefully reconsider their management options, and land use change is likely to result from different crop selections that are more appropriate to the changing conditions. Perhaps the greatest impact of climate change on soils will arise from climate-induced changes in land use and management.     

Stable boundary layers: observations,models and variability part II: Data analysis and averaging effects

As argued in Part I (Derbyshire, 1995), variability is a key issue in stable boundary layers, and differences in variability between observations and idealized models may imply sytematic biases. Here we discuss how data analysis can be geared to allow for variability and thus consistency with models. Instrumental errors, smoothing methods and vertical discretization are considered. We then show how statistical averaging broadly improves the agreement of heterogeneous results in Part I with the Brost-Wyngaard closure. Recommendations are made for the information needed to analyze apparent differences between homogeneous and heterogeneous stable boundary layers.Part of UK Meteorological Office Atmospheric Processes Research Division     

Sufferer and cause: Indian livestock and climate change

Climate change poses formidable challenge to the development of livestock sector in India. The anticipated rise in temperature between 2.3 and 4.8°C over the entire country together with increased precipitation resulting from climate change is likely to aggravate the heat stress in dairy animals, adversely affecting their productive and reproductive performance, and hence reducing the total area where high yielding dairy cattle can be economically reared. Given the vulnerability of India to rise in sea level, the impact of increased intensity of extreme events on the livestock sector would be large and devastating for the low-income rural areas. The predicted negative impact of climate change on Indian agriculture would also adversely affect livestock production by aggravating the feed and fodder shortages. The livestock sector which will be a sufferer of climate change is itself a large source of methane emissions, an important greenhouse gas. In India, although the emission rate per animal is much lower than the developed countries, due to vast livestock population the total annual methane emissions are about 9–10 Tg from enteric fermentation and animal wastes.     

Decentralization, forests and livelihoods: Theory and narrative

This paper discusses the theory of decentralized forest management, the associated narrative and the underlying hypotheses. That discussion informs the assessment of whether decentralization can lead to forest conservation. The paper argues that the ideal model of democratic decentralization described in the literature is unlikely to be implemented given the governance constraints present in many tropical forest countries. Even if that model could be implemented, it is shown that decentralization cannot be expected to necessarily lead to forest conservation. The policies required to complement the current decentralization model are discussed, including financial incentives and monitoring and evaluation mechanisms.     

Seasonal and Diurnal Ozone Variations: Observations and Modeling

Ozone mixing ratios observed by the Bordeaux microwave radiometer between 1995 and 2002 in an altitude range 25–75 km show diurnal variations in the mesosphere and seasonal variations in terms of annual and semi-annual oscillations (SAO) in the stratosphere and in the mesosphere. The observations with 10–15 km altitude resolution are presented and compared to photochemical and transport model results.Diurnal ozone variations are analyzed by averaging the years 1995–1997 for four representative months and six altitude levels. The photochemical models show a good agreement with the observations for altitudes higher than 50 km. Seasonal ozone variations mainly appear as an annual cycle in the middle and upper stratosphere and a semi-annual cycle in the mesosphere with amplitude and phase depending on altitude. Higher resolution (2 km) HALOE (halogen occultation experiment) ozone observations show a phase reversal of the SAO between 44 and 64 km. In HALOE data, a tendancy for an opposite water vapour cycle can be identified in the altitude range 40–60 km.Generally, the relative variations at all altitudes are well explained by the transport model (up to 54 km) and the photochemical models. Only a newly developed photochemical model (1-D) with improved time-dependent treatment of water vapour profiles and solar flux manages to reproduce fairly well the absolute values.     

The Gaia Hypothesis: Conjectures and Refutations

The uncertainties surrounding global climate change provide ample evidence, if any were necessary, of the need for a whole-system view of the Earth. Arguably the most visible – and controversial – attempt to understand Earth as a system has been Lovelock's Gaia theory. Gaia has been a fruitful hypothesis generator, and has prompted many intriguing conjectures about how biological processes might contribute to planetary-scale regulation of atmospheric chemistry and climate. In many important cases, however, these conjectures are refuted by the available data. For example, Gaia theory predicts that the composition of the atmosphere should be tightly regulated by biological processes, but rates of carbon uptake into the biosphere have accelerated by only about 2% in response to the 35% rise in atmospheric CO₂ since pre-industrial times. Gaia theory would predict that atmospheric CO₂ should be more sensitively regulated by terrestrial ecosystem uptake (which is biologically mediated) than by ocean uptake (which is primarily abiotic), but both processes are about equally insensitive to atmospheric CO₂ levels. Gaia theory predicts that biological feedbacks should make the Earth system less sensitive to perturbation, but the best available data suggest that the net effect of biologically mediated feedbacks will be to amplify, not reduce, the Earth system's sensitivity to anthropogenic climate change. Gaia theory predicts that biological by-products in the atmosphere should act as planetary climate regulators, but the Vostok ice core indicates that CO₂, CH₄, and dimethyl sulfide – all biological by-products – function to make the Earth warmer when it is warm, and colder when it is cold. Gaia theory predicts that biological feedbacks should regulate Earth's climate over the long term, but peaks in paleotemperature correspond to peaks in paleo-CO₂ in records stretching back to the Permian; thus if CO₂ is biologically regulated as part of a global thermostat, that thermostat has been hooked up backwards for at least the past 300 million years. Gaia theory predicts that organisms alter their environment to their own benefit, but throughout most of the surface ocean (comprising more than half of the globe), nutrient depletion by plankton has almost created a biological desert, and is kept in check only by the nutrient starvation of the plankton themselves. Lastly, where organisms enhance their environment for themselves, they create positive feedback; thus Gaia theory's two central principles – first, that organisms stabilize their environment, and second, that organisms alter their environment in ways that benefit them – are mutually inconsistent with one another. These examples suggest that the further development of Gaia theory will require more deliberate comparison of theory and data.     

Precipitation Change: Model Simulations and Paleoreconstructions

Zonal-scale patterns of precipitation change, as reconstructed for the Mid-Pliocene and the two Pleistocene optima, are compared with those generated in standard 2 × CO₂–1 × CO₂ equilibrium experiments by two high-resolution GCMs of equal sensitivities of global precipitation and temperature to CO₂ doubling. We find that the three warm paleoclimates, despite differences in boundary conditions/forcings, exhibit a similarity in zonal-scale patterns of change for precipitation over land in the Northern Hemisphere (NH); the between-epoch pattern correlation is 0.9 on the average. The two models give marked differences in zonal distribution of precipitation anomalies at mid-latitudes; the between-model pattern correlation for changes of precipitation over NH land is 0.4. The response of precipitation over the NH land area to the NH warming is about 10%/°C in the paleodata compared to 3%/°C in the models. The largest model/paleodata descrepancy refers to the present-day desert belt, where a large precipitation anomaly persists in all epochs. North of 50 N, the absolute values of the zonally-averaged precipitation anomalies simulated by both models fall in the range implied by the three warm paleoclimates, but they are systematically lower than the anomalies of the Mid-Pliocene. If our reconsructions are valid and if climate changes in the Mid-Pliocene were driven solely by CO₂ changes, then our results suggest that models are underestimating the magnitude of the precipitation response, especially in the regions of subtropical deserts; the magnitude of the simulated temperature response at high latitudes is also underestimated. At least part of the reported model/paleodata discordance appears to be due to lack of interactive land surface package in the models examined.     

Global carbon mechanisms: lessons and implications

We outline the theoretical and political background to the global carbon mechanisms and how they emerged in the form of the Kyoto Protocol??s Clean Development Mechanism, Joint Implementation, and Intergovernmental Emissions Trading. We present empirical data on the response to date and the variants that have arisen. Based on this, we analyse the issues and evidence on the main controversies around additionality, efficiency and effectiveness of the instruments. The final part of the paper considers some of the implications for future development.