The National Academies Press

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Pages 29-46

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From page 29... ... CHANGES IN RAINFALL AND STREAMFLOW Increases of precipitation in high latitudes and drying of the already semi-arid regions at lower latitudes are projected with increasing global warming, with seasonal changes in several regions expected to be about 5-10% per degree of warming. However, patterns of precipitation change show much larger variability across models than patterns of temperature. Read the entire page →
From page 30... ... FIGURE O.1 Estimated changes in precipitation per degree of global warming in the three driest consecutive months at each grid point from a multi-model analysis using 22 models (relative to 1900-1950 as the baseline period) Read the entire page →
From page 31... ... Thus, warming of a few degrees can be expected to lead to large perturbations to water resources, especially in the southwestern and southern parts of the United States, many of which are already facing water resources challenges due to growing population and environmental issues. {5.3} CHANGES IN EXTREME TEMPERATURE, PRECIPITATION, AND CLIMATE DYNAMICS Temperature Extremes Extreme temperatures are expected to increase in a warmer world. Read the entire page →
From page 32... ... Each pair consisted of an average over A2,O2.epsB1 global emissions scenarios of one IPCC As A1B, and sessment Report 4 (AR4) GCM model's output, derived from 30-year runoff averages centered on the years bitmap for which the global average temperature increases were 1.0°C, 1.5°C, and 2.0°C, minus the 30-year model average runoff for 1971-2000, divided by the global temperature change. Read the entire page →
From page 33... ... is likely to increase roughly by 1-4% per degree C global warming, or by 3-12% per degree C for the cube of this wind speed, often taken as a rough measure of the destructive potential of storm winds. For the North Atlantic, the changes in hurricane statistics are more uncertain than the global values, depending in large part on the spatial structure of the warming of the tropical oceans, and not just on the local warming in the Atlantic. Read the entire page →
From page 34... ... Models project a clearly defined linear relationship between annual Arctic sea ice area decreases and global averaged surface air temperature. According to an analysis of an ensemble of models, annually averaged Arctic sea ice area reductions of about 15% are expected per degree C of global av erage warming (see Figure O.4) Read the entire page →
From page 35... ... The relationship between annual average sea ice area and the global average temperature suggests that ice recovery may occur if temperatures decrease. {4.7} Snow Cover and Snowpack Current trends in snow cover over the Northern Hemisphere suggest that the snow cover season has shortened and spring melt is occurring earlier compared to the past 50-100 years. Read the entire page →
From page 36... ... {4.7} Ice Sheets and Glaciers Ice mass loss is occurring in some parts of Greenland and Antarctica, but contributions of the great ice sheets to sea level rise of coming decades and the next century remain uncertain. For 1993-2003, the estimated contri butions to sea level rise (SLR) Read the entire page →
From page 37... ... Global sea level rise is a consequence of global warming and is caused by ocean water expansion and loss of ice stored on land (glaciers, small ice caps, and ice sheets) Read the entire page →
From page 38... ... As a point of comparison, the global Local Warming (C˚) for: Low Latitudes 0 1.2 2.4 3.6 4.8 Mid-High Latitudes 0 1.5 3.0 4.5 6.0 FIGURE O.5 Projected changes in yields of several crops worldwide as a function of global warming (relative to pre-industrial temperatures) Read the entire page →
From page 39... ... These estimates do not include additional losses due to weeds, insects, and pathogens, changes in water resources available for irrigation, effects of increased flood or drought frequencies, or responses to temperature extremes. {5.1} Global warming of 2°C would be expected to lead to average yield losses of U.S. Read the entire page →
From page 40... ... may experience a decrease in wildfires, because warming without increases in precipitation would reduce biomass production and hence limit the avail ability of fuel. Uncertainties include understanding of local soil moisture changes with global warming. Read the entire page →
From page 41... ... OVERVIEW OF CLIMATE CHANGES AND ILLUSTRATIVE IMPACTS 41 FIGURE O.6 Percent increase (relative to 1950-2003) in median annual area burned for ecoprovinces of the West with a 1°C increase in global average temperature. Read the entire page →
From page 42... ... Observations indicate a strong negative relationship between marine primary productivity and warming in the tropics and subtropics, most likely due to reduced nutrient supply, and low-latitude primary production is projected to decline on basin-scales under future climate warming. Primary production in some temperate and polar regions is projected to increase due to warming, reduced vertical mix ing, and reduced sea ice cover. Read the entire page →
From page 43... ... Indirect impacts of ocean acidification on non-calcifying organisms and marine ecosystems as a whole are possible but more difficult to characterize from present understanding. {5.8} Impacts of 21st Century Sea Level Rise Depending on socioeconomic development, population growth, and intensity of adaptation, it has been projected that 0.5 m of sea level rise would increase the number of people at risk from coastal flooding each year by between 5 and 200 million; as many as 4 million of these people could be permanently displaced as a result. Read the entire page →
From page 44... ... {5.2} Infrastructure Impacts Climate change impacts on infrastructure -- including transportation, buildings, and energy -- are primarily driven by changes in the frequency and intensity of temperature extremes and heat waves, heavy rainfall and snow events, and sea level rise. Many impacts are directly tied to changes in climate thresholds, such as number of days above or below a certain temperature, or amount of rainfall accumulated in a 24-hour period, rather than mean temperatures. Read the entire page →
From page 45... ... The frequency and severity of heat waves in Europe and North America are projected to increase under climate change. Under a 2°C increase in global mean temperature, for example, the average number of days per year with maximum temperatures exceeding 38°C or 100°F across much of the south and central United States could increase by a factor of 3 relative to the 1961-1990 average. Read the entire page →
From page 46... ... 46 CLIMATE STABILIZATION TARGETS CO2 levels affect the length of the pollen season and the characteristics of the plans themselves, with some species shown to increase their pollen producing capacity and even their toxicity. {5.6} Ecology and Ecosystems For at least the past 40 years, many species have been and are currently shifting the phenology (timing) Read the entire page →

From page 29...

... CHANGES IN RAINFALL AND STREAMFLOW Increases of precipitation in high latitudes and drying of the already semi-arid regions at lower latitudes are projected with increasing global warming, with seasonal changes in several regions expected to be about 5-10% per degree of warming. However, patterns of precipitation change show much larger variability across models than patterns of temperature.