addressing climate change adaptation in regional transportation plans

Addressing Climate Change Adaptation in Regional Transportation PlansA Guide for California MPOs and RTPAsSummer average temperatures will increase more quickly than winteraverage temperatures.Average inland areas are likely to increase more quickly than coastal regions.Extreme heat events will become more common, last longer, and cover largerareas.Temperature changes over the next 30 to 40 years are already largelydetermined by past emissions. By 2050, temperatures are projected toincrease by an additional 1.8 to 5.4°F, regardless of future emissions.After 2050, temperature projections diverge for different emission scenarios.By 2100, the models project temperature increases between 3.6 to 9°F.PrecipitationProjected changes in precipitation are less clear cut than for temperature. Theseasonal pattern of cool and wet winters and hot and dry summers, typical of aMediterranean climate, is likely to continue. However, the amount ofprecipitation is likely to change, but where and how much rain and snowfalldiffers with both model and emission scenario. Based on Cayan et al. (2012), theprojections suggest the followingThe majority of models suggest drier conditions by mid-century (5 to8 percent less rainfall) with drier conditions persisting through the end of thecentury (9 to 12 percent less annual rainfall);More precipitation will fall as rain rather than as snow, with importantimplications for water resources;Higher temperatures hasten snowmelt and increase evaporation, which willmake for a generally drier climate; andRainfall and meltwater will run off earlier in the year.Sea-Level RiseSea level has been measured at the Presidio tide gauge in San Francisco since1854, which has recorded a rise in relative sea level of 7.6 inches per century inthe last 100 years (NRC, 2012). Rates of relative sea-level rise vary along thecoast in relation to vertical land movement: the observed rise per century is8.0 inches in San Diego, 3.3 inches in Los Angeles, and 2.7 inches in Port SanLuis; and is falling in Crescent City at a rate of 2.9 inches per century (NRC 2012,Table 4.6). Present sea-level rise projections suggest that global sea levels in the21 st century can be expected to be much higher, which will result in higher ratesof relative sea-level rise. These projections are summarized in the State ofCalifornia Sea-Level Rise Interim Guidance Document (OPC, 2010); and have beenincorporated into the Caltrans Guidance on Incorporating Sea-Level Rise (Caltrans2011):3-4 Cambridge Systematics, Inc.