Effects of Global Warming

So, what are the implications again?

"Present CO₂ concentrations in the atmosphere are 130% of pre-industrial levels. The surface temperature this century is warmer than any other century since at least 1400 A.D. The temperature has increased by about 0.5 - 1.1° F over the last century and is projected to rise another 2 - 6.5°F by the year 2100. The last two decades have been the warmest in this century. Sea level has risen about 4 to l0 inches and is projected to rise another 6 - 38 inches by the year 2100. Mountain glaciers have retreated worldwide this century." LINK

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Background

Socially important water issues generally involve water cycle variability. This variability is evidenced, for example, in droughts, which can severely strain water and energy supplies, and floods, which are usually accompanied by infrastructure damage and sometimes by loss of life. The demands on finite water resources and potential damage from droughts and floods are increasing steadily with world population. Quantifying and understanding variations in the water cycle -- and the extent to which humans can modify them or work around them -- is thus becoming increasingly critical.

Any useful analysis of hydrological variability must consider a broad range of spatial scales. At the global scale, water transport is controlled by atmospheric circulation patterns, which are determined in part by ocean temperatures and evaporative fluxes. Land-ocean contrasts in these variables lead to the development of monsoons, which have a tremendous impact on the climates of many regions. At continental scales, precipitation at the land surface is balanced by evapotranspiration, surface and subsurface moisture storage, and streamflow. The quantification of streamflow flux and its dependence on complex continental geomorphology and land cover is critical in managing water resources over large areas. At regional and local scales, convective precipitation is influenced by the structure of the atmosphere near the land surface, the boundary layer, and thus by the nature of the land surface, which is subject to human modification. At these scales, soil, vegetation, geological, and topographic structures lead to unique streamflow and groundwater behavior.

Characterizing hydrological variability also requires considering multiple time scales. Variability at decadal and longer time scales is evidenced, for example, in the Pacific Decadal Oscillation¹ at decadal time scales, and in the paleoclimatic record at even longer (decadal to century) time scales. The El Niño phenomenon, which has significant hydrological impacts throughout the world, has a typical repeat interval of several years. Droughts occur over seasonal to interannual time scales, while individual precipitation events and the physical mechanisms that control them occur over time scales of minutes to hours. Superimposed on these modes of variability are slow "permanent" trends that may be caused in part by increasing concentrations of greenhouse gases and land cover change. LINK

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LINK to an EPA Webpage :

"Climate Change Expected to Lead to Stronger Hurricanes

A comprehensive new computer modeling study suggests that hurricanes will become more intense as the climate warms, with stronger winds and heavier rainfall. The study projects an average 6 percent increase in maximum hurricane winds by the year 2080, along with an 18 percent increase in the rate of precipitation within 60 miles (100 kilometers) of the storm’s core. The increase in intensity amounts to roughly a half step in the 5-category hurricane scale. These specific projections are based on the assumption that carbon dioxide concentrations in the atmosphere will increase by 1 percent per year (compounded) over the next 80 years, which is higher than the current rate of about 0.6 to 0.7 percent per year.

The study’s authors do not expect the changes in hurricane intensity to be detectable “for decades to come,” but warn that there may be a gradually increasing risk of highly destructive category 5 storms over the course of this century.

The study’s basic findings are consistent across nine different climate models and a range of characterizations of physical processes in a hurricane model, bolstering the conclusions. Previous studies based on input from one climate model had also shown a tendency toward stronger hurricanes in warmer climates, but it was unclear how much of this effect was due to assumptions in the model.

The authors, Thomas R. Knutson of NOAA’s Geophysical Fluid Dynamics Laboratory (Princeton, New Jersey) and Robert Tuleya of Old Dominion University (Norfolk, Virginia) did not explore whether climate change would affect the frequency of hurricanes. Past research on this question has been inconclusive, with conflicting results. Knutson and Tuleya’s findings are reported in the 15 September 2004 issue of the Journal of Climate (vol. 17, pp. 3477-3495)." SAME LINK