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California Department of Transportation
Caltrans Transportation Planning Planning Offices Office of Regional and Interagency Planning Climate Change Branch

About Climate Change

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What is the greenhouse effect?

earth, sun.jpghttp://science.howstuffworks.com/environmental/green-science/global-warming.htm
The sun provides energy necessary for life on earth.  Energy in the form of heat from the sun enters the earth’s atmosphere where some is absorbed by the earth and some is reflected back into space.  Greenhouse gases (GHGs) naturally present in the atmosphere absorb the reflected heat, warming the planet.    These GHGs work in a very delicate balance to regulate our climate by trapping heat, acting like a blanket around the earth.    Without GHGs, the planet would be too cold to support life as we know it, but as the amount of GHGs in the atmosphere increases, this blanket effect is intensified and the atmosphere warms at an exponential rate.  This phenomenon is known as the greenhouse effect. 

http://climate.nasa.gov/images/normPage-3.jpg - Good image

What is the difference between weather and climate?

Weather is local (city level) and short-term (weeks to months).  If it rains in your town next week, that is weather.   Weather describes temperature, precipitation, cloudiness, wind etc. which can change minute-to-minute, month-to-month, season-to-season.
Climate refers to the average weather conditions over long periods of time (years) across large areas (states and countries).  An easy way to remember the difference is climate is what you expect, like a wet winter and weather is what you get, a warm clear day (NASA).   

Is climate change the same phenomenon as global warming?

Although very closely related, climate change and global warming are slightly different however; the two terms are often interchanged.  Global warming is what is causing the climate to change.  As GHGs are increasingly released into the atmosphere, temperatures increase.   Global warming is a planet-wide phenomenon.

Climate change refers to the numerous effects of global warming, including temperature changes, storms, changes to precipitation patterns, and rising sea levels.  Climate change refers to the changes on a regional or local level.

How is the climate in California changing?

  • Temperature
    Overall temperatures in California are expected to increase in the future.  The largest temperature increases are projected to occur during summer months in the evening hours.  Extreme heat events will occur more often and cover larger areas.
  • Precipitation
    It is unclear how precipitation patterns will change in the future. The California Energy Commission projects that in the higher elevations, precipitation will fall as rain rather than snow.  This will have major implications on the state water system.
  • Extreme Events
    California has already experienced extreme weather related impacts to the transportation system. Extreme events such as wildfires, floods, droughts, and intense storms will become occur more frequently and be more severe.
  • Attach fact sheet

What will the impact of these changes be on the transportation system in California?

  • Extreme Heat
    According to the California Energy Commission, California has been warming at a rate consistent with worldwide averages.  Extreme heat events in the state are expected to become more common, last longer and affect large areas.  Impacts of extreme heat events include; buckling or cracking of concrete, thermal expansion of bridge joints, warping of railroad tracks, and may require roadwork be conducted at night during cooler temperatures.
    Attach fact sheet
  • Sea-Level Rise
    California has over 1,000 miles of coastline with major population centers and significant transportation infrastructure.  Changes in sea level especially during storm events at high tide could pose great threat to transportation infrastructure including roadways, rail lines, ports, airports, and underground rail and subway facilities. 
    In addition to flooded infrastructure bridges are vulnerable to scour.  Scouring occurs when swift moving water removes sediment from the base of bridge supports.  Scour greatly compromises bridge integrity, and can lead to bridge failure.  As sea levels rise, and extreme storms occur more often, the threat of catastrophic scour is increased.
  • Precipitation Changes
    California is expected to retain its Mediterranean climate of cool wet winters and warm dry summers.  Overall, it is unlikely that typical seasonal precipitation patterns will change drastically, however significant regional variations are expected. 
    It is expected that the Sierra Nevada mountain range will get more precipitation in the form of rain rather than snow which will affect runoff and increase the potential for landslides and roadway washout.  Changes in the timing and intensity of precipitation events could lead to more rock and snow slides and slope failure.  Traditionally dry regions that experience more extreme events are at high risk for system disruption from washouts.

Why is Caltrans concerned with climate change? 

Continued global warming could lead to environmental impacts to the state’s transportation infrastructure and if not addressed, could increase long term costs for the maintenance and operation of the state highway system and could impair public mobility and safety. 

What is Caltrans doing in response to climate change?

Caltrans supports climate change mitigation measures, practices, and business operations to minimize GHG emissions.  We advocate and support sustainable practices throughout all Caltrans activities to help mitigate for future climate change and adapt to climate impacts on the State Highway System.     
Garth Hopkins
Chief, Office of Regional & Interagency Planning
garth_hopkins@dot.ca.gov
(916) 654-8175		 La Nae Van Valen
Senior Transportation Planner
la_nae_van_valen@dot.ca.gov
(916) 657-4458
Julia Biggar
Associate Transportation Planner
julia_biggar@dot.ca.gov
(916) 654-6344
 Rachel Cotroneo
Associate Environmental Planner
rachel_cotroneo@dot.ca.gov
(916) 654-2618
Susan Ejlalmaneshan
Transportation Planner
susan_ejlalmaneshan@dot.ca.gov
(916) 653-3362