气候变化对农业影响评价方法研究进展

近年来,在全球气候变化背景下,气候变化的影响评价研究越来越受到各国科学家和政府的重视,特别是对农业的影响评估研究更为重要.文章主要对观测和模拟在气候变化对农业的影响评价研究中的应用进展进行了介绍,并对该领域未来的研究方向进行了展望,认为加强研究极端天气气候事件的影响;发展农业影响评价集成模式;进一步利用区域气候模式嵌套农业影响评价模式对区域气候变化的影响进行评价,并对其影响的不确定性进行评估.     

Meeting Concentration Targets in the Post-Kyoto World: Does Kyoto Further a Least Cost Strategy?

Preliminary analysis based on an aggregate model of global carbon emissions suggests that constraining emissions to the levels that would be imposed by compliance with the results of the Kyoto negotiations can increase the discounted cost of ultimately limiting atmospheric concentrations. Kyoto targets can be either too restrictive or too permissive depending upon the (currently unknown) trajectory of carbon emissions over the near- to medium-term and the (as yet unspecified) concentration target that frames long-term policy. The discounted cost of meeting low concentration targets like 450 ppmv. is diminished by allowing large sinks and/or by imposing more restrictive near-term emissions benchmarks (even if only Annex B countries are bound by the Kyoto accord). Conversely, the cost of achieving high concentration targets like 650 ppmv. is diminished by disallowing sinks and/or by imposing less restrictive emissions benchmarks. Intermediate concentration targets like 550 ppmv. look like high concentration targets (favoring no sinks and expanded near-term emissions) along low emissions paths; but they look like low concentration targets (favoring the opposite) along high emissions paths. Emissions trajectories that lie above the median, but not excessively so, represent cases for which adjustments in the Kyoto emissions benchmarks and/or negotiated allowances for sinks have the smallest effect on the cost of mitigation.     

Simulated seasonal movement of precipitation zone in rainy season over China and its change on CO_2-doubling

In this paper, an investigation of simulated monthly precipitations from April to September is made. Though the precipitations are sometimes overestimated or underestimated, the geographical advance and recession of precipitation zones are well simulated by the UKMO global climate model with a simple mixed-layer ocean. Main characteristics of large-scale precipitation distribution are changed less on CO2-doubling, but the change is significant in some regions. The change in precipitation threatens us while the dry region is imposed by rainfall defect or the wet region by abundant rainfall induced by CO2-doubling.     

Active Amplification of the Terrestrial Albedo to Mitigate Climate Change: An Exploratory Study

To date, international efforts to mitigate climate change have focussed on reducing emissions of greenhouse gases in the energy, transportation and agriculture sectors, and on sequestering atmospheric carbon dioxide in forests. Here, the potential to complement these efforts by actions to enhance the reflectance of solar insolation by the human settlement and grassland components of the Earth's terrestrial surface is explored. Preliminary estimates derived using a static two dimensional radiative transfer model indicate that such efforts could amplify the overall planetary albedo enough to offset the current global annual average level of radiative forcing caused by anthropogenic greenhouse gases by as much as 30% or 0.76 Wm^{− 2}. Terrestrial albedo amplification may thus extend, by about 25 years, the time available to advance the development and use of low-emission energy conversion technologies which ultimately remain essential to mitigate long-term climate change. While a scoping analysis indicates the technical feasibility of sufficiently enhancing human settlement and grassland albedos to levels needed to achieve reductions in radiative forcing projected here, additional study is required on two fronts. Firstly, the modelled radiative forcing reductions are static estimates. As they would generate climate feedbacks, more detailed dynamic climate modelling would be needed to confirm the stationary value of the radiative forcing reduction that would result from land surface albedo amplification. Secondly, land surface albedo amplification schemes may have important economic and environmental impacts. Accurate ex ante impact assessments would be required to validate global implementation of related measures as a viable mitigation strategy.     

Effects of Climate Change on Population Persistence of Desert-Dwelling Mountain Sheep in California

Abstract:  Metapopulations may be very sensitive to global climate change, particularly if temperature and precipitation change rapidly. We present an analysis of the role of climate and other factors in determining metapopulation structure based on presence and absence data. We compared existing and historical population distributions of desert bighorn sheep ( Ovis canadensis ) to determine whether regional climate patterns were correlated with local extinction. To examine all mountain ranges known to hold or to have held desert bighorn populations in California and score for variables describing climate, metapopulation dynamics, human impacts, and other environmental factors, we used a geographic information system (GIS) and paper maps. We used logistic regression and hierarchical partitioning to assess the relationship among these variables and the current status of each population (extinct or extant). Parameters related to climate—elevation, precipitation, and presence of dependable springs—were strongly correlated with population persistence in the twentieth century. Populations inhabiting lower, drier mountain ranges were more likely to go extinct. The presence of domestic sheep grazing allotments was negatively correlated with population persistence. We used conditional extinction probabilities generated by the logistic-regression model to rank native, naturally recolonized, and reintroduced populations by vulnerability to extinction under several climate-change scenarios. Thus risk of extinction in metapopulations can be evaluated for global-climate-change scenarios even when few demographic data are available.     

PREDICTING CHANGE IN NON-LINEAR SYSTEMS

Complex systems are characterizedby surprising switches to new behaviours. Evaluating and predicting these changes demands anunderstanding of the behaviour of the whole system. The combined ecosystem-climate system shows chaoticor pseudorandom behaviour, stochastic or trulyrandom behaviour, as well as simple bifurcation andsemi-stability. Semistability involves the suddenchange from a destabilized attractor to a newstable attractor which may occur after an apparentlyunpredictable time delay. We present some recentresults for analyzing time series data and for usingsimulations of non-linear models to predict these changes.     

On the optimal control of carbon dioxide emissions: an application of FUND

This paper presents the Climate Framework for Uncertainty, Negotiation and Distribution (FUND), an integrated assessment model of climate change, and discusses selected results. FUND is a nine‐region model of the world economy and its interactions with climate, running in time steps of one year from 1990 to 2200. The model consists of scenarios for economy and population, which are perturbed by climate change and greenhouse gas emission reduction policy. Each region optimizes its net present welfare. Policy variables are energy and carbon efficiency improvement, and sequestering carbon dioxide in forests. It is found that reducing conventional air pollution is a major reason to abate carbon dioxide emissions. Climate change is an additional reason to abate emissions. Reducing and changing energy use is preferred as an option over sequestering carbon. Under non‐cooperation, free riding as well as assurance behaviour is observed in the model. The scope for joint implementation is limited. Under cooperation, optimal emission abatement is (slightly) higher than under non‐cooperation, but the global coalition is not self‐enforcing while side payments are insufficient. Optimal emission control under non‐cooperation is less than currently discussed under the Framework Convention on Climate Change, but higher than observed in practice. This revised version was published online in July 2006 with corrections to the Cover Date.     

Monitoring the Hydrology of Canadian Prairie Wetlands to Detect the Effects of Climate Change and Land Use Changes

There are millions of small isolatedwetlands in the semi-arid Canadian prairies. These`sloughs' are refuges for wildlife in an area that isotherwise intensively used for agriculture. They areparticularly important as waterfowl habitat, with morethan half of all North American ducks nesting inprairie sloughs. The water levels and ecology of thewetlands are sensitive to atmospheric change and tochanges of agricultural practices in the surroundingfields. Monitoring of the hydrological conditions ofthe wetlands across the region is vital for detectinglong-term trends and for studying the processes thatcontrol the water balance of the wetlands. Suchmonitoring therefore requires extensive regional-scaledata complemented by intensive measurements at a fewlocations. At present, wetlands are being enumeratedacross the region once each year and year-roundmonitoring is being carried out at a few locations. Theregional-scale data can be statistically related toregional climate data, but such analyses cast littlelight on the hydrological processes and have limitedpredictive value when climate and land use arechanging. The intensive monitoring network has providedimportant insights but it now needs to be expanded andrevised to meet new questions concerning the effects ofclimate change and land use.     

Adaptation to What and Why?

Adaptation in response to anthropogenic climate change seeks to maintain viability by maximising benefits and minimising losses. It is necessary because some climatic change is now inevitable, despite the international focus on mitigation measures. Indeed, the measures agreed at Kyoto would by themselves result in only a small reduction in the climate changes to be expected over the next century.Discussion of the expected changes and possible impacts leads to the following conclusions regarding climate change scenarios in relation to impacts and adaptation: Climate change in the foreseeable future will not be some new stable "equilibrium" climate, but rather an ongoing "transient" process; Climate change predictions relevant to impacts on most sectors and ecosystems are still highly uncertain; There is a need for a greater focus on developing countries and tropical regions, and on relevant key variables, including the magnitude and frequency of extreme events; The focus should shift from single predictions, or extreme ranges of uncertainty, to risk assessment; Thresholds critical to impacted sectors and ecosystems should be identified, and expressed as functions of climatic variables; Planned adaptations will be necessary to cope with multiple stresses, including those due to non-climatic changes; A major task of adaptation science is to identify the limits of adaptation, i.e., to identify "dangerous levels of greenhouse gases" beyond which adaptation becomes impractical or prohibitively expensive.     

The Kyoto Protocol and non-CO2 Greenhouse Gases and Carbon Sinks

Many trace constituents other than carbon dioxide affect the radiative budget of the atmosphere. The existing international agreement to limit greenhouse gases, the Kyoto Protocol, includes carbon dioxide (CO₂), methane (CH₄), nitrous oxide (N₂O), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), sulfur hexafluoride (SF₆) and credit for some carbon sinks. We investigate technological options for reducing emissions of these gases and the economic implications of including other greenhouse gases and sinks in the climate change control policy. We conduct an integreated assessment of costs using the MIT Emissions Prediction and Policy Analysis (EPPA) model combined with estimates of abatement costs for non-CO₂ greenhouse gases and sinks. We find that failure to take advantage of the other gas and sink flexibility would nearly double aggregate Annex B costs. Including all the GHGs and sinks is actually cheaper than if only CO₂ had been included in the Protocol and their inclusion achieves greater overall abatement. There remains considerable uncertainty in these estimates, the magnitude of the savings depends heavily on reference projections of emissions, for example, but these uncertainties do not change the overall conclusion that non-CO₂ GHGs are an important part of a climate control policy.