Showing papers on "Runaway climate change published in 1998"

Climate forcings in the Industrial era

Abstract: The forcings that drive long-term climate change are not known with an accuracy sufficient to define future climate change. Anthropogenic greenhouse gases (GHGs), which are well measured, cause a strong positive (warming) forcing. But other, poorly measured, anthropogenic forcings, especially changes of atmospheric aerosols, clouds, and land-use patterns, cause a negative forcing that tends to offset greenhouse warming. One consequence of this partial balance is that the natural forcing due to solar irradiance changes may play a larger role in long-term climate change than inferred from comparison with GHGs alone. Current trends in GHG climate forcings are smaller than in popular "business as usual" or 1% per year CO2 growth scenarios. The summary implication is a paradigm change for long-term climate projections: uncertainties in climate forcings have supplanted global climate sensitivity as the predominant issue.

Toward a Real Global Warming Treaty

Abstract: In December 1997 the worlds nations met in Kyoto to grapple with the problem of global warming The Kyoto conference garnered a wide variety of assessments, ranging from "a notable success" through "a useful first step ' to "a grave disappointment and setback" for those concerned with the future of the planet Whatever one thinks of Kyoto in terms of environmentalist politics, the troubling fact remains that its underlying approach is bound to fail Because it is premised on setting national emissions targets, the Kyoto strategy will not be able to solve the alleged problem of global climate change resulting from greenhouse gas emissions The likely failure of Kyoto should be used as the impetus for a hard look at the prospects for a treaty on global climate change The Framework Convention on Climate Change signed in 1992 in Rio de Janeiro drew wide international attention to the danger of gradual global warming from humanity's use of fossil fuels and other activities Rio committed signatory governments to do something about global climate change, but it did not commit them to take any specific actions Since Rio, governments of most rich countries under took to reduce their levels of carbon dioxide emissions to estimated

A climate change scenario for the tropics

Abstract: This paper describes the construction of a climate change scenario for a region representing the ‘extended’ Tropics — 30° N to 30° S — using a methodology that combines results from a simple climate model and a Global Climate Model (GCM) transient climate change experiment. The estimated date by which this climate change scenario might be realized ranges from as early as the end of the 2030s to as late as well into the 22nd century. The central estimate is for this scenario to describe the climate of the 2060s, which would represent a global warming rate of about 0.2 °C per decade, with associated atmospheric CO2 concentrations estimated to be about 560 ppmv, 55% higher than 1990 levels. The role of anthropogenic aerosols in offsetting part of this future global warming and altering the regional character of the changes has not been considered. The paper presents changes in mean temperature; mean rainfall; rainfall seasonality, variability, frequency, and intensity and soil moisture. These patterns of change derive from only one GCM climate change experiment; different experiments would yield different patterns for the same global warming. There is also some discussion about possible changes in tropical cyclone (TC) activity, although since TCs remain poorly modelled in GCMs, the full range of possibilities (from reduced activity, through no change, to increased activity) should be considered in any impact assessment.

A common-sense climate index: Is climate changing noticeably?

Abstract: We propose an index of climate change based on practical climate indicators such as heating degree days and the frequency of intense precipitation. We find that in most regions the index is positive, the sense predicted to accompany global warming. In a few regions, especially in Asia and western North America, the index indicates that climate change should be apparent already, but in most places climate trends are too small to stand out above year-to-year variability. The climate index is strongly correlated with global surface temperature, which has increased as rapidly as projected by climate models in the 1980s. We argue that the global area with obvious climate change will increase notably in the next few years. But we show that the growth rate of greenhouse gas climate forcing has declined in recent years, and thus there is an opportunity to keep climate change in the 21st century less than "business-as-usual" scenarios.

Simulations of Climate and Climate Change

Abstract: The difference between “weather” and “climate” is often a common source of misconception and not always clearly defined. A typical definition is that given by the Webster dictionnary (1994), which states that climate is “the average course or condition of the weather at a place usually over a period of years as exhibited by temperature, wind velocity, and precipitation”. The IPCC (1996) defines climate in its simplest term as “the average weather”. Both these definitions are insufficient to truly differentiate between “weather” and “climate”, however, because the notion of temporal scale is not sufficiently emphasized.

Climate Processes and Change

Abstract: The 1997 Kyoto summit on climate change demonstrates the world community's desire to protect future generations from harmful effects induced by the anthropogenic emission of greenhouse gases. On the other hand, the worldwide impacts of the 1997–1998 El Nino Southern Oscillation (ENSO) event serve as a reminder of how natural variability can strongly influence weather. In this book, Bryant provides a bird's-eye view of natural climate change over the last 2 million years, rather than the fish's-eye view of the more recent possible anthropogenic global warming. The key feature that sets this text apart is the perspective of climate change on a larger timescale. The author recognizes that climate is not constant, and that only small perturbations are necessary to shift climate into an extreme state. If this is the case, however, anthropogenic greenhouse gas forcing may also produce extreme climate change. Climate Processes and Change also differs from other texts by raising the awareness of uncertainties in historical observations, trends, and the complex and nonlinear relationships between observations and theory.

Unlocking the climate puzzle.

Abstract: Global climate depends on compounding factors interacting in subtle and complex ways that have not been fully understood In 1995 a study by the Intergovernmental Panel on Climate Change (IPCC) concluded that there is a discernible human influence on global climate Although specific consequences of human activity are ambiguous such an ability to alter the atmosphere is incontestable In view of such it is noted that studies on climate patterns are helping scientists make projections on future climate changes in the world In the case of the greenhouse effect it has been projected that in the next 100 years global average temperatures will rise by 1-35 degrees This warming of the magnitude anticipated by the IPCC could prompt widespread calamity A most probable effect is that the average amount of precipitation in any given event will be greater In turn an increased precipitation may cause dry regions to become more arid and many wet areas to experience increased rainfall However it is noted that these projections have been made with the use of general circulation models which have been known to provide only a range of projected temperature change resulting in uncertainty of the projections

Simulation of the thermal regime of permafrost in northeast china under climate warming

Abstract: Changes in the thermal regime of permafrost are generally determined by climatic processes under natural conditions and climatic or ground surface changes caused by human activities. One of the latter concerns is global climatic warming caused by increasing concentration of greenhouse gases in the atmosphere. Scientists predict that climate warming caused by manOs activities will far exceed those from natural processes during the next century. The IPCC impact assessment on climate change (1990) gives a consequent increase of the global mean annual temperature in the range of 1.5¼C to 4~5¼C for a doubling of CO 2 in the atmosphere between now and the years 2025 to 2050 under a Obusiness-as-usualO scenario. The 1995 report predicts a rise in the global mean surface temperature of about 1~3.5¼C using climate models that take into account greenhouse gases and aerosols by 2100 (IPCC, 1996). Climate warming could result in an increase in active layer thickness overlying permafrost, a rise in ground temperatures, and thinning of permafrost. Research concerning future changes in the geothermal regime of permafrost is therefore important for analyzing present construction, determining design principles for different types of construction, and determining its influence on the geological environment under a warming climate. The response of permafrost thickness and ground temperature to climate change under continuous warming is likely to be disequilibrium. Changes in the permafrost geothermal regime are dependent not only on an increase in air temperature, but also on (1) the ground moisture content, including ice and unfrozen water, the thermal conductivity and specific heat capacity of frozen and unfrozen ground, (2) the geothermal gradient below the permafrost base, (3) the annual range of air temperature changes in the local regions, and (4) the ground surface conditions. Therefore, the response of permafrost to climatic change will differ in different sectors of the same region and in different regions.

Energy and Climate

Abstract: The climatic changes caused by the increasing release of “greenhouse gases” into the earth’s atmosphere will exceed all previous environmental crises in their scope. In spite of considerable uncertainties in interpreting already existing data and models (see Box on p.130 [4.1]) as well as in the prevailing opinion of experts, an overall warming of the lower atmosphere from anthropogenic influences is considered probable [4.2; 4.3].

Role of aerosols in radiative forcing of climate change: Global mean and uncertainties

Abstract: Anthropogenically induced climate change is of great current interest because of increases in atmospheric loading of infrared active (greenhouse) gases over the past 150 years and the inferred resultant increase in infrared radiation flux in the troposphere. However, the climate change ascribed to such increases, not to mention predictions of future climate change in response to prospective changes in the earth`s radiation budget, is based virtually entirely on climate model simulations of how the earth`s climate would respond to changes in radiation rather than on empirically established relationships between changes in the earth`s radiation budget and climate change. There is thus an urgent need to evaluate the performance of climate models to ascertain the accuracy with which they represent the changes in temperature and other indicia of climate that have been observed over the industrial period. Such an evaluation, however, requires an accurate assessment of the totality of changes in the earth`s radiation budget in both the longwave (thermal infrared) and shortwave (solar) spectral regions, not just of changes in the longwave due to increased concentrations of long-lived greenhouse gases.