addressing climate change adaptation in regional transportation plans

Addressing Climate Change Adaptation in Regional Transportation PlansA Guide for California MPOs and RTPAsWhat is the Significance of Changes inExtreme Climate?The type and frequency of extreme eventsare expected to change at the global scaleand can occur even with small changes inclimate means.Shifts in mean climate conditions canexacerbate extreme conditions resulting inhigher, more frequent, and more prolongedheat waves, greater flooding and erosionimpacts of coastal storm surges, and shifts inwatershed runoff and timing. In planning foradapting transportation infrastructure to thechanging climate, trends in extreme eventswill play a major role in understanding therisk to transportation assets.Source: Mastrandrea et al., 2009. Precipitation projections show more variabilitybetween models and emission scenarios. Ingeneral, longer dry spells will become morecommon with occasional intense rainfall events. Occasional intense rainfall events will continueto occur, with no significant change in the trend ofprojected frequency of heavy precipitation events. The frequency of large coastal storms andheavy precipitation events does not appear tochange significantly over the 21 st century.However, storms will still impact the coast moreseverely due to higher sea levels that can result inhigher storm surges, more extensive inlandflooding, and increased erosion.3.3 CLIMATE CHANGE PROJECTIONS AND SCENARIOMODELINGWhat is the Difference between a ClimateProjection and a Prediction?Due to the inherent uncertainty in theevolution of global economic and technologicfactors future climate scenarios representprojections, rather than predictions, of futureclimate conditions. Projections consider arange of plausible pathways in globalresource use (emissions), differences inglobal climate models, and varying estimatesof climate sensitivity to emissionconcentrations. This range represents thedistribution of uncertainty in the many toolsused to project future climate conditions.The range and timing of climate changeimpacts under a variety of possible futureconditions provides a spectrum of climatechange risk which serves as the basis foradaptation planning.Predicting human-induced changes in climate overthe next 100 years requires: A prediction of global GHG emissions for thenext century. A global carbon cycle model to convert theseemissions into changes in carbon dioxideconcentrations (and similar models for calculatingconcentrations of other GHG and aerosols). A general circulation model (GCM), which usesthe GHG and aerosol concentration information toproject future climate variations. Downscaling of the GCM results to a regionallevel through a procedure which takes account ofthe influence of topography on local climate. Thiscan be done either statistically or with a higherresolution regional climate model (RCM).3-6 Cambridge Systematics, Inc.