Environmental Policy Collection - 31 Matching Results

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Thresholds of Climate Change in Ecosystems

Description: This Report (SAP 4.2) focuses on the thresholds of Climate Change in Ecosystems. As defined in this Synthesis and Assessment Report, 'an ecological threshold is the point at which there is an abrupt change in an ecosystem quality, property, or phenomenon, or where small changes in one or more external conditions produce large and persistent responses in an ecosystem'.Ecological thresholds occur when external factors, positive feedbacks, or nonlinear instabilities in a system cause changes to propagate in a domino-like fashion that is potentially irreversible. This report reviews threshold changes in North American ecosystems that are potentially induced by climatic change and addresses the significant challenges these threshold crossings impose on resource and land managers. Sudden changes to ecosystems and the goods and services they provide are not well understood, but they are extremely important if natural resource managers are to succeed in developing adaptation strategies in a changing world. The report provides an overview of what is known about ecological thresholds and where they are likely to occur. It also identifies those areas where research is most needed to improve knowledge and understand the uncertainties regarding them. The report suggests a suite of potential actions that land and resource managers could use to improve the likelihood of success for the resources they manage, even under conditions of incomplete understanding of what drives thresholds of change and when changes will occur.
Date: January 2009
Creator: U.S. Climate Change Science Program and the Subcommittee on Global Change Research
Partner: UNT Libraries

Trends in Emissions of Ozone-Depleting Substances, Ozone Layer Recovery, and Implications for Ultraviolet Radiation Exposure

Description: This Synthesis and Assessment Product (SAP 2.4) focuses on the Climate models. Depletion of the stratospheric ozone layer by human-produced ozone-depleting substances has been recognized as a global environmental issue for more than three decades, and the international effort to address the issue via the United Nations Montreal Protocol marked its 20-year anniversary in 2007. Scientific understanding underpinned the Protocol at its inception and ever since. As scientific knowledge advanced and evolved, the Protocol evolved through amendment and adjustment. Policy-relevant science has documented the rise, and now the beginning decline, of the atmospheric abundances of many ozone-depleting substances in response to actions taken by the nations of the world. Projections are for a return of ozone-depleting chemicals (compounds containing chlorine and bromine) to their "pre-ozone-depletion" (pre-1980) levels by the middle of this century for the midlatitudes; the polar regions are expected to follow suit within 20 years after that. Since the 1980s, global ozone sustained a depletion of about 5 percent in the midlatitudes of both the Northern Hemisphere and Southern Hemisphere, where most of the Earth's population resides; it is now showing signs of turning the corner towards increasing ozone. The large seasonal depletions in the polar regions are likely to continue over the next decade but are expected to subside over the next few decades.
Date: November 2008
Creator: US Climate Change Science Program and the Subcommittee on Global Change Research.
Partner: UNT Libraries

Uses and Limitations of Observations, Data, Forecasts, and Other Projections in Decision Support for Selected Sectors and Regions

Description: This Synthesis and Assessment Product (SAP), Uses and Limitations of Observations, Data, Forecasts, and Other Projections in Decision Support for Selected Sectors and Regions. This is part of a series of 21 SAPs produced by the CCSP aimed at providing current assessments of climate change science to inform public debate, policy, and operational decisions. This SAP focuses on the use of climate observations, data, forecasts, and other projections in decision support.
Date: August 2008
Creator: U.S. Climate Change Science Program and the Subcommittee on Global Change Research
Partner: UNT Libraries

Weather and Climate Extremes in a Changing Climate : Frequently Asked Questions

Description: This brochure corresponds with the Weather and Climate Extremes in a Changing Climate Synthesis and Assessment Report by the U.S. Climate Change Science Program. It highlights observed changes and likely projections in North American weather, and how changes in North American weather are likely to have an adverse economic effect.
Date: 2008
Creator: Climate Change Science Program (U.S.)
Partner: UNT Libraries

Weather and Climate Extremes in a Changing Climate. Regions of Focus: North America, Hawaii, Caribbean, and U.S. Pacific Islands

Description: This document is part of the Synthesis and Assessment Products described in the U.S. Climate Change Science Program (CCSP) Strategic Plan. Changes in extreme weather and climate events have significant impacts and are among the most serious challenges to society in coping with a changing climate. This Synthesis and Assessment Product (SAP 3.3) focuses on weather and climate extremes in a changing climate. Many extremes and their associated impacts are now changing. For example, in recent decades most of North America has been experiencing more unusually hot days and nights, fewer unusually cold days and nights, and fewer frost days. Heavy downpours have become more frequent and intense. Droughts are becoming more severe in some regions, though there are no clear trends for North America as a whole. The power and frequency of Atlantic hurricanes have increased substantially in recent decades, though North American mainland land-falling hurricanes do not appear to have increased over the past century. Outside the tropics, storm tracks are shifting northward and the strongest storms are becoming even stronger. It is well established through formal attribution studies that the global warming of the past 50 years is due primarily to human-induced increases in heat-trapping gases. Such studies have only recently been used to determine the causes of some changes in extremes at the scale of a continent. Certain aspects of observed increases in temperature extremes have been linked to human influences. The increase in heavy precipitation events is associated with an increase in water vapor, and the latter has been attributed to human-induced warming. No formal attribution studies for changes in drought severity in North America have been attempted. There is evidence suggesting a human contribution to recent changes in hurricane activity as well as in storms outside the tropics, though a confident assessment will require ...
Date: June 2008
Creator: U.S. Climate Change Science Program and the Subcommittee on Global Change Research.
Partner: UNT Libraries