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SAN LEANDRO SHORELINE DEVELOPMENT DRAFT EIR <br />CITY OF SAN LEANDRO <br />GREENHOUSE GAS EMISSIONS <br />ages, and the global mean temperature is rising at a rate that cannot be explained by natural causes <br />alone. 14 Human activities are directly altering the chemical composition of the atmosphere through the <br />buildup of climate change pollutants.t5 <br />Projections of climate change depend heavily upon future human activity. Therefore, climate models are <br />based on different emission scenarios that account for historic trends in emissions as well as observations <br />on the climate record that assess the human influence of the trend and projections for extreme weather <br />events. Climate -change scenarios are affected by varying degrees of uncertainty. For example, climate <br />trends include varying degrees of certainty on the magnitude of the direction of the trends for: <br />■ warmer and fewer cold days and nights over most land areas; <br />■ warmer and more frequent hot days and nights over most land areas; <br />■ an increase in frequency of warm spells/heat waves over most land areas; <br />■ an increase in frequency of heavy precipitation events (or proportion of total rainfall from heavy falls) <br />over most areas; <br />■ areas affected by drought increases; <br />■ intense tropical cyclone activity increases; and <br />■ increased incidence of extreme high sea level (excludes tsunamis). <br />IPCC's "2007 IPCC Fourth Assessment Report" projects that the global mean temperature increase from <br />1990 to 2100 under different climate -change scenarios will range from 1.4 to 5.8 degrees Celsius (2.5 to <br />10.4 degrees Fahrenheit). In the past, gradual changes in the earth's temperature changed the <br />distribution of species, availability of water, etc. However, human activities are accelerating this process so <br />that environmental impacts associated with climate change no longer occur in a geologic time frame, but <br />within a human lifetime.16 <br />Potential Climate Change Impacts for California <br />Like the variability in the projections of the expected increase in global surface temperatures, the <br />environmental consequences of gradual changes in the Earth's temperature are also hard to predict. In <br />California and western North America, observations of the climate have shown: 1) a trend toward warmer <br />winter and spring temperatures, 2) a smaller fraction of precipitation falling as snow, 3) a decrease in the <br />amount of spring snow accumulation in the lower and middle elevation mountain zones, 4) shift in the <br />timing of snowmelt of 5 to 30 days earlier in the spring, and 5) a similar shift (5 to 30 days earlier) in the <br />timing of spring flower blooms." According to the California Climate Action Team—a committee of State <br />agency secretaries and the heads of agency, boards, and departments, led by the Secretary of the <br />California Environmental Protection Agency—even if actions could be taken to immediately curtail climate <br />14 At the end of the last ice age, the concentration of CO2 increased by around 100 ppm (parts per million) over about <br />8,000 years, or approximately 1.25 ppm per century. Since the start of the industrial revolution, the rate of increase has <br />accelerated markedly. The rate of CO2 accumulation currently stands at around 150 ppm/century—more than 200 times faster <br />than the background rate for the past 15,000 years. <br />15 California Climate Action Team, 2006. Climate Action Team Report to Governor Schwarzenegger and the Legislature, <br />March. <br />16 Intergovernmental Panel on Climate Change, 2007. Fourth Assessment Report: Climate Change 2007, New York: <br />Cambridge University Press. <br />17 California Climate Action Team, 2006. Climate Action Team Report to Governor Schwarzenegger and the Legislature, <br />March. <br />PLACEWORKS 4.6-5 <br />