Scripps Researchers Assess the Future of Climate in California

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Scripps Institution of Oceanography, UC San Diego, climate scientists on the latest understanding of climate impacts on California of concern to the state's economic future

  1. What are the most serious threats facing Northern California because of climate change?
  2. What are the most serious threats facing Southern California because of climate change?
  3. How will climate change affect precipitation and water availability in California?
  4. How will rising sea levels affect coastal communities? Are certain parts of California's coastline more vulnerable to sea-level rise than others?
  5. How will climate change affect the health of the Pacific Ocean?
  6. To what extent will climate change increase the frequency and severity of heat waves in California? Which part(s) of the state will be most affected by heat waves? How severe will these heat waves be? Which populations will be most vulnerable to the effects of these heat waves?
  7. To what extent will climate change increase the frequency and severity of wildfires in California? Which parts of the state are likely to be most affected?
  8. What impact will climate change have on agriculture in California, including production of field crops, fruits and nuts, and vegetables?
  9. How will climate change affect the Sacramento-San Joaquin Delta? What repercussions could there be for the rest of the state?
  10. How will climate change affect the reliability of the state's electricity system?
  11. What other critical infrastructure in California could be affected by climate change?
  12. Will climate change impacts in California have broader national consequences? If so, how?
  13. Is it reasonable to expect that climate change could harm California's economic competitiveness? If so, please explain how.
  14. Is there other information regarding the impacts of climate change on California that you would like to share?

Contributors

1) What are the most serious threats facing Northern California because of climate change?

Climate Change projections, from a growing ensemble of international climate modeling centers, indicate that global and regional climate in California will continue to shift to a warmer climate during the next several decades.   The changes that are projected will result in a climate that is warmer than the warmest climate that modern Californians have experienced historically (IPCC 2007).  Thus it is expected that climate change will impact, broadly, most of the human and natural systems in Northern and Southern California.  Among the many symptoms of climate change, the following components and impacts are likely to pose challenges in Northern California:

  • Heat waves—increase in intensity, duration, frequency and humidity, which impact population, supply and demand for energy and water, and natural systems in California. With more frequent, more intense and more long-lasting heat waves there is the potential for an increase in heat-related illness to the public, animals, and plants.
  • Sea-level rise, as it impacts people, property, infrastructure, and water supply along the northern California coast and estuaries (especially the San Francisco Bay/Sacramento and San Joaquin Delta). 
  • Loss of spring snowpack in Sierra Nevada and other mountain regions which depend on snow for water supply, ecosystem services, and recreation.
  • Increased wintertime flood frequency and intensity, especially in watersheds that are currently fed by snowmelt runoff.
  • Increase in wildfires, especially in forested areas of Sierra Nevada and coast ranges.
  • Increase in pests, a challenge to farmers in Central Valley and other agricultural regions. Some insects (e.g. mosquitos) may change their range and population dynamics, possibly creating a greater threat of vector-borne diseases, which may affect humans and animals.
  • Ecosystem impacts in many of Northern California’s rich, diverse, and unique ecosystems.
  • Electrical system impacts, as they affect the supply and transmission and demand for electricity, especially during summer when electrical demand reaches its peak.

2) What are the most serious threats facing Southern California because of climate change?

  • Heat waves—increase in intensity, duration, frequency and humidity, which impact population, supply and demand for energy and water, and natural systems in California. With more frequent, more intense and more durable heat waves there is the potential for an increase in heat-related illness to the public, animals and plants.
  • Sea-level rise as it impacts people, property, infrastructure, and water supply along the southern California coast.
  • Water supply shortage and diminished reliability to domestic, industrial, and agricultural users who depend on both local and imported (Northern California and Colorado River) water. 
  • Increase in wildfires, especially in forested regions of Southern California, which are prone to increased wildfire threat as summers become hotter and drier, and the dry “fuel” season becomes longer and possibly more intense. 
  • Air quality degradation, in particular atmospheric ozone increases, which threatens human and ecosystem health. California’s two most problematic air basins are the Los Angeles and the San Joaquin air basins.  
  • Larger floods from moister winter storms, especially in settings where hill and mountain slopes act to generate heavy precipitation.  
  • Pests, a challenge to farmers in Central Valley and other agricultural regions. Some insects (e.g. mosquitos) may change their range and population dynamics, possibly creating a greater threat of vector-borne diseases, which may affect humans and animals.
  • Ecosystem impacts in many of Southern California’s rich, diverse, and unique ecosystems.
  • Electrical system impacts, as they affect the supply and transmission and demand for electricity, especially during summer when electrical demand reaches its peak.

3) How will climate change affect precipitation and water availability in California?

California has an extremely volatile precipitation climate with the greatest year-to-year variation of annual total precipitation in the United States.  Climate change is expected to affect the delivery of water to California in the following ways:

  1. A potential impact of climate change will occur if the amount of precipitation changes.  A complication is that global climate models indicate that precipitation change over California is not well defined, but several models exhibit a general move toward drier conditions in the very southern parts of California and somewhat wetter conditions in Northern California.  These changes are superimposed upon the familiar structure of great interannual variability.  There are a lot of differences amongst the models, which emphasizes the large uncertainty in the precipitation projections, and also underscores the importance of using the projections with caution.  In a composite of several models, the patterns of change of precipitation start to appear in the first 30 years of the record, and become stronger by the end of the 21st Century.  There is more agreement among the models that there will be seasonal shifts in precipitation, with somewhat more during winter and less during the spring.  Such a change might pose operating or regulatory challenges for California’s water managers, because in some cases, winter precipitation may not be able to be stored in order to preserve reservoir capacity for possible flood flows.
  1. Another climate change impact, which is quite certain to occur, is that as our climate warms, the precipitation that falls in California’s high-yield mountain watersheds is going to shift toward more immediate rainfall runoff rather than storing water in the snowpack.  This transition has already begun—most low and middle elevation stations exhibit trends toward more rain and less snow, and snow courses at these elevations are recording lower amounts of water content in the snowpack in relation to the amount of precipitation they have received.  In association with these changes, there has been a decline in the proportion of later season runoff; this has important implications because the late spring-summer runoff is vital to ecosystem function, as well as for agriculture and other human consumptions.  With substantial, progressive warming projected over the 21st Century, the amount of water stored in the California snowpack in spring will continue to decline.  Estimates are for losses of 50% to more than 75% of the present-day April 1 snow water content by 2100 using recent climate model projections. This is very significant considering California’s dry summers – a basic feature of California’s Mediterranean-type climate that is not expected to change.
  1. Another effect involving changes in the California water cycle is that precipitation in the most intense storm events may become more intense as the atmosphere moistens due to increases in the ocean evaporation and spin-up of the global hydrological cycle.  Thus, despite California’s seat in a semi-arid climate zone, the potential for the occurrence of occasional great floods may increase.  
  1. Another possible set of impacts will be felt when droughts occur. Well before modern settlement in the medieval period, there is evidence that Central California was gripped by a decades-long drought.  While intense dry spells have occurred during the more recent era (indicated by recent tree rings and instrumental data), they did not occur in an era with markedly warmer temperatures.   Also, during the modern era, droughts that we have experienced did not have the long duration that is indicated by proxy evidence (sediments, tree rings) of extreme droughts during the medieval period. Any natural drought cycles will be exacerbated by warmer temperatures that will increase evaporation as well as demand for fresh water.
  1. Finally, water availability may be compromised because of the loss of the spring snowpack, greater evaporative losses, vegetative demand for water, and likely declines in snowmelt-fed Colorado River flows, which make up an important part of Southern California’s water supply. Warming in regions such as the Western United States implies that sustainability of reliable water supplies will require changes in water management. These adaptations will potentially exacerbate conflicts of water allocation to meet human demands and goals of biological conservation plans.

4) How will rising sea levels affect coastal communities? Are certain parts of California’s coastline more vulnerable to sea-level rise than others?

Sea-level rise under current estimates will approach or exceed 1 meter above present day mean sea level by 2100, a rate of rise that is much greater than recent historical rates over the last several hundred years.  The greatest impacts will occur when sea-level rise is compounded by the effects of a severe storm on top of high tides, further amplified by a short term heightened sea level driven by El Niño conditions.  In other words, extreme waves and tides on top of rising sea level will be more extreme and impactful.  Such events will affect ecosystems, structures, and people. By the end of the 21st Century, if sea level rises at the upper end of projected rates, conditions during large winter storms will inundate critical infrastructure along the California Coast, including roads, hospitals, schools, emergency facilities, wastewater treatment plants, and power plants. Low-lying areas and wave-exposed areas of California’s open coast are most vulnerable to sea-level rise.  Sea-level rise could drive greater erosion of California’s beaches, which are an important tourist attraction and driver of economic activity in many of the state’s coastal communities. Replenishing beaches is expensive, and armoring beaches diminishes their tourist appeal. California’s abilities to  plan and cope with pending sea-level rise issues have a relatively sound scientific foundation, but are still challenged by institutional and economic obstacles. 

Additionally, estuaries are vulnerable, including the San Francisco Bay/Delta, which is the West Coast’s largest estuary and a key hub of the California water system.

5) How will climate change affect the health of the Pacific Ocean?

Climate change due to the human addition of CO2 and other greenhouse gases to the atmosphere has four main effects on ocean health. First, the ocean warms, affecting weather, density stratification, ocean circulation, and marine ecosystems, including fisheries. Second, sea level rises, affecting storm surge, inundation, wetlands and estuaries, and beach and cliff erosion. Third and fourth, ocean oxygen is decreasing and acidity is increasing, affecting ecosystems, including fisheries. These four processes are of varying importance in oceanic, coastal, and nearshore (surf zone and beach) regions.

All four effects are important to California and the Pacific Ocean.  Storm frequency and intensity, hence severity, are predicted to increase, with effects on commerce and safety. Fish habitats are predicted to decrease due to density stratification and deoxygenation, affecting fisheries and aquaculture. Shifts of spawning centers of some marine fishes have already occurred. In the absence of mitigation efforts, shellfish production is predicted to decrease due to ocean acidification Harmful algal blooms, which affect ecosystems, fisheries, aquaculture, and recreation (e.g., beaches), have increased and may continue to increase in occurrence. Tourism and recreation, including beach-going, fishing, boating, surfing, and whale watching are predicted to be affected by sea-level rise, deoxygenation, acidification, and warming. The physical and chemical basis for these effects is well known and widely accepted. Thus, the four main processes are predicted with a high degree of confidence. The response of ecosystem services to these processes continues to be a focus of research.

There is some evidence for intensified coastal upwelling of deep waters off California, possibly due to a warming-induced temperature differential between land and sea. The upwelled waters off California, naturally low in oxygen and pH, may act to modify coastal ecosystems in several ways including: (1) reduction of suitable habitat for midwater and benthic organisms, causing habitat compression and avoidance movements that alter species interactions and increase susceptibility to harvest  (2) exposure of sessile and less mobile species or life stages to oxygen stress (hypoxia) or low pH (acidification) with consequences for California’s fisheries and aquaculture, especially for calcifying species like mussels, clams, and oysters; and (3) enhancing primary production that may benefit some species (e.g., large fish,) but lead to greater microalgial respiration and further oxygen/pH reductions. Macrophyte habitats (kelp, seagrass, marsh grass), by removing CO2, may provide important, localized refuges from these effects and thus could require special consideration as a remediation tool.  Many questions remain about the ability of organisms to adapt to changing conditions in the ocean, and this is a major subject for research at present. Climate change will interact with other types of stressors imposed by human activities in coastal waters, including altered circulation, habitat modifications, pollution, and introductions of invasive species, which are reshaping the coastal environment with unpredictable consequences for the resilience of coastal ecosystems and the ecosystem services upon which humans depend.  

6) To what extent will climate change increase the frequency and severity of heat waves in California? Which part(s) of the state will be most affected by heat waves? How severe will these heat waves be? Which populations will be most vulnerable to the effects of these heat waves?

Virtually all climate model projections indicate that average conditions will warm during the next several decades as greenhouse gases continue to accumulate in the atmosphere.  Estimates are that heat wave frequency, duration, and intensity will increase markedly over the 21st Century.  For example, models suggest that by the mid 2060s, four out of five Julys in Sacramento will be hotter than the hottest July experienced since record-keeping began. Similar results are found for other areas in the state. Models also project that although all locations will warm, the relative increment in temperature during the worst heat waves will be greatest along the coast.

This has energy and public health implications, since the state’s population density is high near the coast and the residents are relatively unused to high temperatures there. The incidence of warm, humid nights is likely to increase disproportionately (Gershunov and Guirguis, 2012), which also has public health implications as it reduces the ability for people and buildings to cool between successive days of high afternoon temperatures.  The flavor of heat waves is also changing; they are becoming more humid and thus hotter at night and this trend is expected to continue. The combination of increasing heat and humidity results in accentuated nighttime (minimum temperature) warming strongly impacts the health people, animals, and plants.

In general, poverty increases susceptibility to extreme weather events and California is not immune to this global rule. During the July 2006 heat wave, 90% of hyperthermia-caused deaths (140 total according to coroners reports) occurred in zip codes where more than 50% of the residents lived below Federal Poverty Threshold (Trent 2007, CDPH). Geographically, although coastal regions are not projected to warm as much as the interior on average in summer, coastal heat waves are projected to become relatively more intense during both day and night. Coastal communities are least acclimated to heat due to marine-influenced cool summers on average and lack of air conditioning penetration (Sailor and Pavlova 2003). Since coastal heat waves are projected to increase by the largest margin relative to typically cool summer coastal temperatures, impacts on public health are expected to be most severe on the densely populated and un-acclimated coastal California.

7) To what extent will climate change increase the frequency and severity of wildfires in California? Which parts of the state are likely to be most affected? 

As summers become longer and hotter and forest fuels get drier, large wildfires are likely to occur more frequently. California’s shrub lands are already dry in summer, and thus warming will probably not produce large changes in fire activity in these regions.  However, climate warming will lead to earlier and more intense seasonal drying of larger tree forest species, and thus would result in greater fuel for wildfires in forested regions.  The drying of forests will likely be exacerbated as spring and early summer snow packs decline due to more rainfall, less snowfall, and earlier snowmelt—researchers have found a sudden and dramatic increase in fires in forested areas in the western United States in the mid 1980s that they link, quite strongly but not entirely, to climate warming. A temperature increase of less than 1 degree Celsius was associated with a 300 percent increase in the number of fires and a 600 percent increase in the areas burned.  The temperature increase also lengthened the fire season by 78 days. The average large fire in the 1970s typically burned for a week. In the 2000s, big fires lasted for an average of five weeks.

Climate model and wildfire model estimates suggest that the frequency and the size (acres burned) of forest fires will increase in future decades.  Model projections indicate that average temperatures will increase by 1.5 degrees C to 5.8 degrees C by the end of the 21st century.  Under these scenarios, there will be markedly more wildfires in the future, and the impacts on people, infrastructure, ecosystems, and carbon storage in the state would be substantial. 

8) What impact will climate change have on agriculture in California, including production of field crops, fruits and nuts, and vegetables?

California is home to a $30 billion agriculture industry that employs more than one million workers. It is the largest and most diverse agriculture industry in the nation, producing more than 300 commodities, including half the country’s fruits and vegetables. Increased heat-trapping emissions are expected to cause widespread changes to this industry, reducing the quantity and quality of agricultural products statewide. Although higher carbon dioxide levels can stimulate plant production and increase plant water-use efficiency, California farmers will face greater water demand for crops and a less reliable water supply as temperatures rise. Crop growth and development will change, as will the intensity and frequency of pest and disease outbreaks. Rising temperatures will likely aggravate ozone pollution, which makes plants more susceptible to disease and pests and interferes with plant growth. Plant growth tends to be slow at low temperatures, increasing with rising temperatures up to a threshold. However, faster growth can result in less-than-optimal development for many crops, so rising temperatures are likely to worsen the quantity and quality of yield for a number of California’s agricultural products. Moreover, exceeding the species-specific temperature thresholds causes dangerous stress. Plants and animals will be more susceptible to increased heat wave activity, in particular.

Commodities that are likely to be hard hit include wine grapes, fruits, and nuts, as well as dairy production. The heat wave of July 2006 resulted in cattle and chicken mortality in the tens of thousands, and severely impacted dairy, poultry, and egg production (USAgNet, 31 July 2006). About 25,000 cattle in central California, or 1% of the dairy herd was lost during that heat wave alone (http://news.bbc.co.uk/2/hi/americas/5223172.stm). Impacts included disruption to animal breeding and 10% reduction in milk production in the Central Valley. Such heat waves are projected to become progressively more common over this century.  Extreme heat impacts have had terrible impacts on cattle and other farm animals in the state, and it is expected that these events could pose an increased threat in the future.  Costs to agriculture from climate change would have consequences not only within California, but to the nation (see response to question 12).  

9) How will climate change affect the Sacramento-San Joaquin Delta? What repercussions could there be for the rest of the state?

The San Francisco Bay is the largest estuary on the US West Coast.  The Bay/Delta is heavily populated and contains critical infrastructure, including water conveyance,  electrical transmission, and roads.  It provides habitat for endemic species and for native fishes, including Pacific salmon and steelhead trout, and has great social and economic significance as the source of runoff that provides drinking water to 25 million people and irrigation water to a million hectares of farmland, producing crops valued at $36 billion per year.

The San Francisco Bay/Delta is an interconnected river network, estuary, and coastal ocean, and thus is affected by multiple factors, underpinned by climate processes and changes that are atmospheric, oceanic, and hydrologic in their nature.  Altered regional patterns of temperature, precipitation and sea level could cascade to provoke local impacts such as modified water supplies, increasing risks of coastal flooding, and growing challenges to the sustainability of native species. 

Catastrophic failure of multiple levees in the Delta would have far-reaching consequences to people, infrastructure, and ecosystems (see response to question 12).  In addition, however, even without a series of levee failures, a recent analysis of two scenarios guided by quite different climate model projections (Cloern et al 2011) yielded the following conclusions:

Today's extremes could become tomorrow's norms.  Biological community changes are inevitable.  Expected outcomes include increasing extinction risk of native species and continuing emergence of nonnative species as dominant components of biological communities. Fishes endemic to the Delta, such as delta smelt, are adapted to cool, turbid, low-salinity habitats. Sustaining populations of these species will become increasingly difficult as Delta waters warm, clear, and become more saline. Of the four runs of Chinook salmon that spawn in the Sacramento-San Joaquin drainage, the winter run is at exceptional risk because its spawning is timed such that eggs develop in summer, when projected river temperatures reach lethal level. Communities of fish and their zooplankton prey in the Delta have become increasingly dominated by nonnative species, whose successful invasions have been facilitated by synergistic effects of climate anomalies (extended drought) and flow management.

The challenge of meeting California's water demands will intensify.  California's water supply (annual unimpaired runoff) is projected to decline or remain steady, and demands are likely to increase as populations and temperatures rise. Deficits of surface runoff are now met with groundwater pumping. However, pumping between 1998 and 2010 depleted 48.5 km3 of water from the Central Valley groundwater system, and continued groundwater depletion at this rate is unsustainable. Future strategies of water management will require adaptations such as aggressively increasing water-use efficiency, reducing surface water deliveries, capturing more runoff in surface storage or groundwater recharge, and implementing programs of integrated regional water management. Model results suggest that the inherent large annual variability of precipitation will persist, even as longer-term trends of warming and possibly drying take hold. Therefore, water-resource planning should also include contingencies for longer dry seasons, extended droughts, and extreme floods due to shifts from snow to rain. Diminishing snow packs result in earlier reservoir inflow, so reservoir operations must adapt to a shift toward more water being managed as a hazard (flood control) and less as a resource (reservoir storage). Additional freshwater releases to mitigate increased salinity intrusion into the estuary will be required to maintain quality of drinking water to communities that use the Delta as their municipal water supply. These adaptations to maintain water supply for human consumptive uses will potentially constrain availability of water to meet objectives of habitat conservation plans, such as restoring natural flow and salinity variability to promote recovery of native biota in the Delta.

10) How will climate change affect the reliability of the state’s electricity system?

Climate change is likely to have a small but harmful impact on the state’s electricity system.  The likely impacts of climate change will be felt mainly in three ways: the state’s hydro system; the effects of heat on long-distance transmission lines; and increased demand for electricity.

California obtains 70% of its electricity from in-state generators.  Of those, 21% are from hydro-electric generation.  All hydro facilities are vulnerable to changes in water flow, but high altitude hydro units are particularly vulnerable because they depend directly on snow pack.  According to a study done for the Third Assessment of Climate Impacts in California, these high-elevation plants account for about three-quarters of California’s in-state hydro power generation and they face substantial challenges in adapting to a shift in snowpack. One of the chief adaptations would be to increase the size of storage reservoirs, which is probably impractical.  One of the major uncertainties in this analysis concerns whether warming will produce drier or wetter outcomes; in dry scenarios generation from these plants might decrease 20% (with a similar but smaller decline in total revenues from operating these power plants) but in wet scenarios there are smaller but positive changes in output and revenues.  Fossil-fired power plants are unlikely to experience great changes in output as a direct response to climate change, although they require water for cooling and outputs from these plants are likely to decline with the regulation of emissions, and that could accelerate a transition to other energy sources such as renewables.  If that transition occurs rapidly and without adequate planning there could be harmful impacts on reliability since wind and solar generators are variable and intermittent in their output, and electric power systems that have integrated large amounts of these energy sources (e.g., Germany, Denmark, West Texas) have already begun to face threats to grid stability and reliability. 

Second, higher temperatures and wildfires from climate change are highly likely to affect the state’s long-distance transmission network.  The rating of power lines is extremely sensitive to heat (hot lines stretch and sag, and sagging lines hit trees and other obstacles that can yield short circuits).  Power lines are also essentially inoperable under conditions of fire.  Adaptations to these climate impacts include more extensive sensor networks that could allow power lines to operate more closely to their theoretical limits as well as redundant networks, although the latter approach is likely to be expensive and probably impractical given the difficulties already in siting new power lines.  Along critical path lines, extreme heat or wildfire could lead to more system blackouts. 

Third, higher temperatures are likely to lead to greater demand for electricity. Over the next century, simulated demand for electricity especially in inland areas (where power is needed for air conditioning) could rise as much as 25%.  Statewide, over the next century total electricity demand could rise 1% to 10% due to climate change alone, with those results highly sensitive to the scenario for climate change that unfolds.

To get an idea of the order of magnitude of these potential combined impacts, researchers have calculated the impact that the high-end temperature projections for the end of this century would have on the current electricity system. Their finding is that under this hypothetical scenario, generating capacity would have to be up to 38 percent higher in comparison to our current climate.  In addition, a warming planet would also reduce energy generation and revenues from hydropower generation a system that currently provides from 10 to 20 percent of the electricity generated in California. Hydropower generation is an important source of electricity during peak demand periods during the hot months of the year. However, this service would be compromised if the number of heat waves or their severity increases, as expected, from a warming planet.  

11) What other critical infrastructure in California could be affected by climate change?

There is no simple answer to this question because infrastructure is highly diverse.  In addition to the likely impacts on the electric power system created by greater demand for power, as well as vulnerabilities in the hydro system and in transmission lines, the effects of climate change will likely impact California’s infrastructure in two ways. 

First, all infrastructure along the coastline and vulnerable to higher sea level and storm surges will be exposed. Sea-level rise due to climate change will increase the risk of failure of levees that protect the islands in the Sacramento-San Joaquin Delta.  Recent studies also indicate that the entire Delta area is subsiding which further reduces the protection afforded by the current levees (Brooks et al., 2012a,b). Water levels are going up with sea-level rise while the levees, and the Delta in general, seem to be experiencing a long-term downward vertical movement.  A major failure of the Delta will impact the supply of water to central and southern California because the Delta is used as a major conveyance facility in the transport of water from Northern California to the more arid parts of the state.  In addition, important energy facilities are located in the Delta, such as underground natural gas storage facilities, natural gas pipelines, and electrical transmission lines (see Figure 1.2 in Lund et al, 2007).  Important coastal infrastructure such as the San Francisco and the Oakland International airports, ports, roads and railways, wastewater treatment plants, buildings, and power plants are also in areas that have been identified as being exposed to increased risk of coastal flooding due to sea-level rise (Herberger et al., 2011).  By the end of this century, Herberger et al. estimated that coastal flooding will threaten up to about $100 billion worth of property in California. Protective measures would be implemented but it is unclear, so far, what specific actions and by when they should be undertaken. An initial study for the Port of Los Angeles suggests at least for the parts of the port investigated, that no immediate protective measures should be implemented but that the vulnerability of the Port of Los Angeles should be considered during the periodic evaluations of major improvements to this important port (Lempert et al., 2012).

Second, some infrastructure is vulnerable to fires, floods, and other extreme events that could become more likely with climate change.  Those include roads and settlements in fire-prone areas, as well as waterways that may need to be resized to handle larger storm surges.  The state’s water transport system could be highly exposed to risk of flood and drought; in a warmer world evaporation from long distance transport is also likely to be higher, leading perhaps to the need for adaptive responses such as covering. 

Public health services could be severely impacted by more frequent and intense heat waves. Impacts of recent heat waves on hospitalizations and emergency department visits were highly significant (Knowlton et al. 2009, Gershunov et al. 2011, Guirguis et al. 2013) and such impacts are expected to become more frequent and intense. Particularly if aggravated by power failures, they can become severe.

12) Will climate change impacts in California have broader national consequences? If so, how?

Yes—California’s food, water, energy, transportation, economy, ecosystems, diseases, regulatory structures, and other institutions are highly linked to other regions of the United States, so that impacts within California and beyond California will influence the State and the nation.

Agriculturally, increased temperatures are estimated to produce an overall reduction in yields for annual crops (Lee et al., 2011) and perennials (Lobell and Field, 2011).  Economic analyses suggest that the impacts would be negative (Schlenker et al., 2007; Deschenes and Kolstad, 2011; Medellín-Azuara et al., 2011), which would increase the cost of food.  The economic costs could be higher than what economic studies have reported, so far, if inland flooding increases in the rest of this century, as is suggested by some scientists (Da et al., 2011).  Historically, inland flooding has been the most costly type of weather related extreme events (Lobell et al., 2011).  California produces approximately 99 percent of a large number of specialty crops such as almonds, grapes, peaches, walnuts, artichokes, and pistachios.  California also produces nearly half of U.S. grown fruits, nuts, and vegetables (CDFA, 2010).  Therefore, negative impacts to California’s agricultural sector from climate change would have national ramifications. 

A potentially catastrophic failure of the levees in the Sacramento-San Joaquin Delta, regardless of the reason for this failure (e.g., a seismic event, flooding due to storms and sea-level rise), would disrupt the transfer of water to about two-thirds of all Californians and to millions of acres of irrigated farmland.  In addition, the important infrastructure already in place in the delta will be affected with unknown cascading effects.  As noted above, important coastal infrastructure could be severely affected by sea-level rise. Given that California contributes about 13 percent of the nation’s economic output, these types of severe economic and social impacts would have national repercussions.

13) Is it reasonable to expect that climate change could harm California’s economic competitiveness? If so, please explain how.

Yes.  California’s competitiveness could be affected by climate change in at least three ways.  First, there may be direct impacts of climate change on productive industries, agriculture is one example (see above), but impacts such as reduction in water availability and increased costs or shortages of electricity in summer would impact a broad range of sectors in the state.  Second, climate change may harm California’s infrastructure.  Essentially all of the world’s most competitive economies have excellent infrastructure, and California (which already struggles to fund and operate its infrastructure effectively) could suffer.  Third, climate change regulation implies extra costs that could affect economic competitiveness—especially in industries that use large amounts of energy.  Already, however, California has relatively high electricity prices, and thanks to extensive reliance on natural gas and renewables, its emissions of warming gases per unit of electric output are relatively low.  Other areas of the country—such as regions that depend heavily on coal-fired electric generation like the Midwest—are likely to see a larger relative increase in energy prices.  On the other hand, emerging problems create opportunities—new technologies that are developed in California can provide resources and services elsewhere, which can provide jobs, and investment in the state.  

14) Is there other information regarding the impacts of climate change on California that you would like to share?

It is crucially important that California realize that its efforts to control emissions must be embedded in an international strategy.  California by itself is just 1% of world emissions.  In order to reduce the emissions that cause dangers from climate change in California, any effort made to control emissions in California should be undertaken with an eye to whether it leverages controls in other jurisdictions as well. This point leads to several practical implications not just for California but also the U.S. Among them is that the adoption of emission trading schemes—as California is now doing under AB32—include opportunities for firms to invest in and earn international offsets, thus helping to ensure that the efforts undertaken in California spread and multiply worldwide (Victor, 2010). 

In addition to assessing potential impacts of climate change, we also need to question the abilities of our social systems to operate effectively in an era in which climate and impacts are not informed by our historical experience. California is only beginning to evaluate the cost of adaptation to climate change.   In some (many?) cases, we have sufficient knowledge to plan and adapt for climate change, but the short term costs (new technical staff, new regulations, and so forth) prevent meaningful action toward solutions—this was underscored by a recent survey of coastal professionals regarding their knowledge and capacity to take action regarding climate changes along the California coast. Climate change will add to and probably exacerbate challenges confronting California from other stressors (population increase, changes in land use, land cover, agriculture, transportation, industry, invasive species, and geopolitics). Some of the greatest changes may occur during extreme events (think of Sandy or Katrina or the 2003 and 2007 wildfires); during such events a number of social and natural systems would likely be affected simultaneously, requiring broad based, cross-cutting action and possibly policy changes. Because we govern and manage at many levels (federal, state, and local), as evidenced by the number of water management entities in California, climate change and the high-impact events will present a different context for thinking about coping (adaptation and mitigation) and will necessitate new partnerships to carry this out.  There are many issues of concern involving built and natural systems, as well as ethical and legal issues. There will be tension across different communities in need of the same resources—the needs of the underserved, the defense of natural systems in the face of growing human demands for resources, and so on. 

Another key issue that is often invisible or given short-shrift is the perpetual struggle by and within agencies, universities, and scientists to collect the information needed for sound decision-making in an era in which information, both short term and long term, is increasingly vital to make sound decisions.  Imagine where we would be were it not for Dave Keeling’s vigilance in sustaining the measurements of CO2 on Mauna Loa.  This is only a single example amongst a myriad of the need for scientific data to support science, decision making and policy across an interconnected web of physical, biological, natural, and human-influenced systems that affect California. 

Historical experience and forward-thinking logic underscores the importance of using and sustaining the best available science for flexible, robust decision-making in the choices California makes to adapt and mitigate climate change impacts. California has had a rich endowment in science expertise and has used this in making progress in assessing impacts and exposing vulnerability to climate change.  But to translate knowledge into action will require continued political leadership and courage, in order to achieve a liveable, thriving future for California.   


Contributors to this report include the following:

Scripps Institution of Oceanography at UC San Diego
Dan Cayan
Dave Checkley
Ralph Keeling
Lisa Levin
Mark Ohman
Alexander Gershunov
David Pierce
Richard Somerville

UC San Diego
David Victor

Collaborators
Guido Franco, California Energy Commission
Susanne Moser, Susanne Moser Consulting

 

 

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