addressing climate change adaptation in regional transportation plans

Addressing Climate Change Adaptation in Regional Transportation PlansA Guide for California MPOs and RTPAsThe warmed Earth emits infrared radiation, which is readily absorbed by GHGin the atmosphere, such as water vapor, carbon dioxide, and methane.Absorption of infrared radiation causes the atmosphere to warm and emit itsown infrared radiation. The Earth’s surface and lower atmosphere warm untilthey reach a temperature where the heat radiation emitted back into space, plusthe directly reflected solar radiation, balance the absorbed energy coming in fromthe sun. As a result, the surface temperature of the Earth is around 59°F onaverage, 90°F warmer than it would be if there was no atmosphere. This is calledthe natural greenhouse effect.If the concentration of GHG is increased, then there will be more absorption ofinfrared radiation. The Earth’s surface and the lower atmosphere will warmfurther until a balance of incoming and outgoing radiation is reached again. Thisextra warming is called the enhanced greenhouse effect. Figure 3.2 shows theobserved increase in global carbon dioxide concentrations over the past 50 years.Its concentration has been building up in the Earth’s atmosphere since thebeginning of the industrial era in the mid-1700s, primarily due to the burning offossil fuels (coal, oil, and natural gas) and the clearing of forests. Humanactivities have also increased the emissions of other GHG, such as methane,nitrous oxide, and halocarbons (Forster et al., 2007).Figure 3.2Atmospheric Carbon Dioxide at Mauna Loa ObservatorySource: National Oceanic and Atmospheric Administration (NOAA), 2010.Figure 3.3 shows that the observed global mean temperature over land and oceanhas also increased over the same time period. The year 2010 tied with 2005 as thewarmest year since records began in 1880. The annual global combined land andocean surface temperature was 1.12°F above the 20 th century average. The 2010combined land and ocean surface temperature in the Northern Hemisphere was3-2 Cambridge Systematics, Inc.