Uptake of anthropogenic CO2 results in gradual acidification of the ocean. The pH of surface seawater has decreased by 0.1 since the beginning of the industrial era, corresponding to a 26% increase in hydrogen ion concentration. The observed pH trends range between a –0.0014 and –0.0024 reduction per year in surface waters. In the ocean interior, natural physical and biological processes, as well as uptake of anthropogenic CO2, can cause changes in pH over decadal and longer time scales (IPCC, 2013).
While more than half of the CO2 emitted is currently removed from the atmosphere within a century, some fraction (about 20%) of emitted CO2 remains in the atmosphere for many millennia. Because of slow removal processes, atmospheric CO2 will continue to increase in the long term even if its emission is substantially reduced from present levels. Methane (CH4) is removed by chemical processes in the atmosphere, while nitrous oxide (N2O) and some halocarbons are destroyed in the upper atmosphere by solar radiation. These processes each operate at different time scales ranging from years to millennia. A measure for this is the lifetime of a gas in the atmosphere, defined as the time it takes for a perturbation to be reduced to 37% of its initial amount. While for CH4, N2O, and other trace gases such as hydrochlorofluorocarbon-22, a refrigerant fluid, such lifetimes can be reasonably determined (for CH4 it is about 12 years, for N2O about 110 years and for HCFC-22 about 12 years). A lifetime for CO2 cannot be defined (IPCC, 2007).
[See page 5-331 for the original comment] The assumptions and calculations for vehicle trips in all scenarios is presented in Section 4.N, Traffic and Circulation, starting on page 4.N-71. Calculations of trip generation are presented in Tables 4.N-12 through 4.N-16.
[See page 5-331 for the original comment] Cumulative impacts of proposed Baylands development, in combination with other past, present, and reasonably foreseeable future projects on specific segments of the US 101 freeway is presented in Table 4.N-33.
Congestion on US 101 results from the combination of trips generated by Brisbane residents and businesses, as well as residents and businesses in San Francisco, San Mateo and Santa Clara counties, and elsewhere.
As stated on page 4.N-74, trip distribution was derived from several reputable sources, including the MTC Regional Travel Demand Model, the Candlestick/ Hunters Point EIR, the Bay Area Travel Survey 2000, the C/CAG Travel Demand Model, and the San Francisco Transportation Impact Analysis Guidelines.