The challenge of identifying greenhouse gas-induced climatic change

Meeting the challenge of identifying greenhouse gas-induced climatic change involves three steps. First, observations of critical variables must be assembled, evaluated, and analyzed to determine that there has been a statistically significant change. Second, reliable theoretical (model) calculations must be conducted to provide a definitive set of changes for which to search. Third, a quantitative and statistically significant association must be made between the projected and observed changes to exclude the possibility that the changes are due to natural variability or other factors. This paper provides a qualitative overview of scientific progress in successfully fulfilling these three steps

The Environmental Effects of Nuclear War

Substantial environmental disruption will significantly add to the disastrous consequences caused by the direct thermal, blast, and radiological effects brought on by a major nuclear war. Local fallout could cover several percent of the Northern Hemisphere with potentially lethal doses. Smoke from post-nuclear fires could darken the skies and induce temperature decreases of tens of degrees in continental interiors. Stratospheric ozone could be significantly reduced due to nitric oxide injections and smoke-induced circulation changes. The environmental effects spread the consequences of a nuclear war to the world population, adding to the potentially large disruptive effects a further reason to avoid such a catastrophe. 27 refs., 4 figs

Climate Change: The Evidence Mounts Up

This article was published in Nature and summarized the presentations of a six-day symposium held 3-8 July 1995 on Climate Variability and Forcing over the past mellennium. Our present climate is unusually warm, and the pattern of warming over the past century strongly suggests an anthropogenic influence from greenhouse gas and sulphate aerosols. That was the message emerging from a week-long symposium examining climate variability over the past 1,000 years, which brought together results from a growing array of observational techniques, analyses of natural records and model results

Mitigation of short-lived greenhouse gases as the foundation for a fair and effective climate compromise between China and the West

Short-lived greenhouse gases that also contribute to air pollution are playing a major role in global warming. Black carbon alone is likely the second or third most important climate forcing agent. The short atmospheric lifetime of these pollutants means that, unlike CO2, reducing emissions produces a decrease in atmospheric concentration and a reduction of the radiative forcing that drives climate change. Black carbon and tropospheric ozone also have large negative effects at the regional and local level contributing substantially to indoor and urban air pollution and the formation of Atmospheric Brown Clouds that disrupt regional climate. Moreover, technologies to reduce emissions are available, cost-effective, and have already been widely deployed in developed countries. Reducing these short-lived greenhouse gases is therefore a mitigation pathway for industrializing countries that is both appropriate to their level of development and highly climatically effective. It is also consistent with both responsibility and capability fairness principles, both of which play important roles in the international climate regime. As such, it offers a way out of the current deadlock between developed and developing countries in which each group asks for more substantial emissions reduction commitments from the other before taking action. China, as the world’s largest black carbon emitter, should push for substantial CO2 mitigation commitments from the developed countries in return for aggressive action to reduce its own soot emissions. This action is consistent with China’s own development strategy and would contribute substantially to the mitigation of climate change

National Assessment of the Potential Consequences of Climate Variability and Change for the United States

The first U.S. National Assessment of the PotentialConsequences of Climate Variability and Change for theUnited States is being conducted under the auspices of theU.S. Global Change Research Program (USGCRP). TheUSGCRP was established through the Global ChangeResearch Act of 1990 (P.L. 101-606) and mandatedthrough the statute with the responsibility to undertakeperiodic scientific assessments of the potentialconsequences of global change for the United States. Thegoal of the National Assessment is to analyze andevaluate what is known about the potential consequencesof climate variability and change for the nation in thecontext of other pressures on the public, the environment,and the nation\u27s resources. The conduct of the nationalassessment process will involve a broad spectrum ofstakeholders from state, local, tribal, and Federalgovernments; business; labor; academia; non-profitorganizations; and the general public. The assessmentwill link research by scientists to specific needs of thestakeholders, and will provide planners, managers,organizations, and the public with the information neededto increase resilience to climate variability and cope withclimate change. The national assessment will becomprised of three components: (1) National synthesis,(2) Sectoral analyses (agriculture, forestry, waterresources, human health, and the coastal zone), and(3) Regional analyses. To facilitate comparison,integration, and synthesis of each of the assessmentcomponents, all regional, sectoral, and synthesis analyseswill use a common set of scenarios for climate change and changes in socio-economic conditions. Specific responsibilities have been defined for oversight of the components of the national assessment and forcoordination activities. A National Assessment SynthesisTeam (NAST) will provide overall intellectual oversightof the national assessment process and has responsibilityfor the development of the Synthesis Report. A NationalAssessment Working Group under the auspices of theUSGCRP has lead responsibility for organizing andsponsoring the sectoral analyses and oversight andcoordination responsibilities for regional analyses. ANational Assessment Coordination Office has beenestablished to facilitate coordination of the entire nationalassessment process. The National Assessment SynthesisReport is targeted for completion by January 1, 2000, andis intended to satisfy the mandate for an assessmentdefined in P.L. 101-606 and serve as part of the U.S.contribution to the IPCC Third Assessment Report

Comprehensive system models: Strategies for evaluation

The task of evaluating comprehensive earth system models is vast involving validations of every model component at every scale of organization, as well as tests of all the individual linkages. Even the most detailed evaluation of each of the component processes and the individual links among them should not, however, engender confidence in the performance of the whole. The integrated earth system is so rich with complex feedback loops, often involving components of the atmosphere, oceans, biosphere, and cryosphere, that it is certain to exhibit emergent properties very difficult to predict from the perspective of a narrow focus on any individual component of the system. Therefore, a substantial share of the task of evaluating comprehensive earth system models must reside at the level of whole system evaluations. Since complete, integrated atmosphere/ ocean/ biosphere/ hydrology models are not yet operational, questions of evaluation must be addressed at the level of the kinds of earth system processes that the models should be competent to simulate, rather than at the level of specific performance criteria. Here, we have tried to identify examples of earth system processes that are difficult to simulate with existing models and that involve a rich enough suite of feedbacks that they are unlikely to be satisfactorily described by highly simplified or toy models. Our purpose is not to specify a checklist of evaluation criteria but to introduce characteristics of the earth system that may present useful opportunities for model testing and, of course, improvement

Decomposition of radiational effects of model feedbacks

Three separate doubled CO/sub 2/ experiments with the statistical dynamic model are used to illustrate efforts to study the climate dynamics, feedbacks, and interrelationships of meteorological parameters by decomposing and isolating their individual effects on radiation transport

Understanding Climatic Impacts, Vulnerabilities, and Adaptation in the United States: Building a Capacity for Assessment

Based on the experience of the U.S. National Assessment, we propose a program of research and analysis to advance capability for assessment of climate impacts, vulnerabilities, and adaptation options. We identify specific priorities for scientific research on the responses of ecological and socioeconomic systems to climate and other stresses; for improvement in the climatic inputs to impact assessments; and for further development of assessment methods to improve their practical utility to decision-makers. Finally, we propose a new institutional model for assessment, based principally on regional efforts that integrate observations, research, data, applications, and assessment on climate and linked environmental-change issues. The proposed program will require effective collaboration between scientists, resource managers, and other stakeholders, all of whose expertise is needed to define and prioritize key regional issues, characterize relevant uncertainties, and assess potential responses. While both scientifically and organizationally challenging, such an integrated program holds the best promise of advancing our capacity to manage resources and the economy adaptively under a changing climate