Levels Of Atmospheric Greenhouse Gases Research Articles

The “faint young Sun paradox”: further exploration of the role of dynamical heat-flux feed backs in maintaining global climate stability

AbstractThe climate-modeling problems associated with global change underline the importance of understanding paleoclimates. The available evidence, which suggests that the Earth has never been fully glaciated, poses an especially serious problem for the early Earth when the Sun was about 20–30% fainter than today. In conventional explanations of this “faint young Sun paradox”, presumed very high levels of atmospheric greenhouse gases are required to prevent runaway glaciation of the Earth. Here we explore other possible explanations of this paradox. As an extension of our previous work on this subject, we illustrate how-dynamical beat-flux feed backs may have prevented the early Earth from freezing. Our simulations are carried out using a two-dimensional, seasonal-climate model with physically based parameterizations for atmospheric meridional-heat transport and sea ice. It ís found that dynamical heat-flux feed backs alone may have protected the Archean Earth against a runaway glaciation to a considerable degree.

Climate and Vegetation Change in the Central Grasslands Biogeographic Area

The purpose of this document is to describe the intent of climate change research being funded by the National Park Service (NPS) in the Central Grasslands (CEGR) Biogeographic Area (BGA). For the purposes of this document, the CEGR BGA is broadly defined as areas of historical or potential grassland extending from the southern Canadian provinces to northern Mexico and from the foothills of the Rocky Mountains to western Indiana. The majority of NPS units containing prairie within this BGA are short-grass, northern mixed-grass, or tall-grass ecosystems. Increasing levels of atmospheric greenhouse gases (C02, CH4, CFCs, etc.) are expected to induce dramatic changes in the world's climate over the next 30-100 years. General circulation model (GCM) simulations for a doubling of C02 have projected 2-3xC increases in mean global temperatures and major transformations of land surface hydrology. Extensive modification of the land surface due to land use changes (e.g. deforestation, irrigation) are also anticipated to have important effects on atmospheric circulation and climate.

The potential effects of climatic change on agricultural insect pests

Climate and weather can substantially influence the development and distribution of insects. Anthropogenically induced climatic change arising from increasing levels of atmospheric greenhouse gases would, therefore, be likely to have a significant effect on agricultural insect pests. Current best estimates of changes in climate indicate an increase in global mean annual temperatures of 1°C by 2025 and 3°C by the end of the next century. Such increases in temperature have a number of implications for temperature-dependent insect pests in mid-latitude regions. Changes in climate may result in changes in geographical distribution, increased overwintering, changes in population growth rates, increases in the number of generations, extension of the development season, changes in crop-pest synchrony, changes in interspecific interactions and increased risk of invasion by migrant pests. To illustrate some of these effects, results of a study investigating the impact of climatic change on the European corn borer ( Ostrinia nubilalis) in Europe are shown. Under the climatic changes projected by the Goddard Institute for Space Studies general circulation model, northward shifts in the potential distribution of the European corn borer of up to 1220 km are estimated to occur, with an additional generation found in nearly all regions where it is currently known to occur. A number of priorities for future research into the effects of climatic changes on agricultural insect pests can be identified. These include: examination of the influence of climatic variables on insect pests, long-term monitoring of pest population levels and insect behaviour, consideration of possible climatic changes in research into pest management systems and identification of potential migrants.

Climate change and the response of forests

Abstract The global climate has warmed by over 0·5°C during the last 125 years. Models of the Earth's temperature reponse to increasing levels of atmospheric carbon dioxide and other greenhouse gases estimate that the average global surface temperature will rise about 4°C by the mid twenty-first century. High latitudes will warm more than lower latitudes and winters more than summers. Forests will undergo enormous changes as temperatures increase and precipitation patterns shift. It is doubtful that forest movement will meet the rate of climate change. Many sensitive hardwood tree species, such as paper and yellow birch, sugar maple and black ash, may die. Boreal forests will replace tundra and mixed hardwood forests will replace them. Much of the change expected in the location and composition of forests may be detected by means of remote sensing.

Law: Environmental Impact Statements and Climate Change

Recent demands by atmospheric scientists and policy makers for immediate, comprehensive, and effective responses to the threat of global climate change have focused political attention on policies and laws that affect the quality of the environment. In January, the Reagan White House blocked the issuance of policy guidance that would have directed federal agencies to consider global climate change in the preparation of environmental impact statements (EIS). The Bush administration now has an early opportunity to reverse this decision. Using detailed computer models of the Earth's climate, atmospheric scientists have produced startling scenarios of the future climate conditions that will results from increased atmospheric levels of greenhouse gases. These projection a predict higher average temperatures, changes in patterns of precipitation, greater seasonal and annual variability in weather, and an increased frequency of such extreme events as droughts and floods. Planning for adaptation to a changing climate will be far more difficult than acting now to reduce greenhouse-gas emissions. While current models depict global changes reasonably well, they cannot accurately predict local and regional changes in the temperature and precipitation patterns. Unresolved questions about future impacts only underscore the need to act now to reduce emissions of greenhouse gases. The soonermore » action is taken, the more effective it will be. If policy responses are delayed, the eventual magnitude of climate change will be greater, and more radical measures will be required. In 1969, the National Environmental Policy Act (NEPA) mandated that every arm of the federal government integrate environmental values into all aspects of work, At the heart of NEPA lies a strict requirement that the preparation of a detailed EIS precede all major Federal actions significantly affecting the quality of the human environment.« less

ASSESSING POTENTIAL CLIMATE CHANGE IMPACTS ON WATER SUPPLY AND DEMAND IN SOUTHERN ALBERTA

The potential effects of climate warming due to increasing atmospheric levels of greenhouse gases are poorly defined. The predicted time frame for significant warming to occur is within the time frame of concern to most water resource planning and development. Some estimates must be made of the potential effects, so that managers and planners may adjust middle and long term policies and programs to deal with reasonable warming scenarios.This study presents a water balance assessment of supply and demand variations for the Oldman River basin in Alberta under a range of climate warming scenarios. The Oldman River basin, as a semi-arid region with intensive water-based development, is regarded as a region with a high-risk of adverse effects due to greenhouse warming. A crop consumptive use model is used to simulate the soil water demands for irrigated crops over the basin under five climate scenarios. Historical irrigation diversion demands are adjusted to reflect the increased crop demands under warming. Th...