A. What is Climate Change?

Climate change refers to long-term changes in temperature, precipitation, wind patterns, and other elements of the earth's climate system. The Intergovernmental Panel on Climate Change (IPCC) defines climate change as "any change in climate over time, whether due to natural variability or as a result of human activity." An ever-increasing body of scientific research attributes these climatological changes to greenhouse gases (GHGs), particularly those generated from the human production and use of fossil fuels.

Return to Top

B. What is the Greenhouse Effect?

Historically, atmospheric gases such as water vapor, carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), ozone (O3), halocarbons (HFC's) and others have trapped terrestrial radiation in the Earth's atmosphere, which has maintained a temperature and climate hospitable to life over much of the Earth. This is a condition known as the "greenhouse effect." Different greenhouse gases have different effects on the Earth's energy balance.

Return to Top

C. Is the Earth Warming?

Scientists believe that the earth is warming faster than at any time in the previous 1,000 years. The average global surface temperature has increased by 1.1 degrees Fahrenheit since the 19th century. The 10 warmest years of the last century all occurred within the last 15 years - 1998 was the warmest year on record. As atmospheric concentrations of greenhouse gases rise, so do temperatures, because less heat is able to escape the atmosphere. This rise in temperature is accompanied by climatic changes, some dramatic and some subtle, that affect how organisms live, adapt, and survive on the planet.

Return to Top

D. How Certain is the Climate Change Science?

While the climate system is very complex and difficult to model precisely, the Intergovernmental Panel on Climate Change (IPCC) is increasingly certain that humans have a discernible influence on the global climate. Confirmation of the measured warming trend is substantiated by the rise in sea level of between four and 10 inches that has occurred since 1900 and the decrease in the average snow cover and glacial ice worldwide. Unseasonable weather phenomena are becoming commonplace and intensities appear to be increasing. A continued increase in greenhouse gas emissions, and the associated temperature rise, is likely to accelerate the rate of climate change, producing further impacts.

The primary greenhouse gas contributor is CO2. Scientists have established direct links between increased CO2 concentrations and the atmospheric warming that has occurred since the industrial revolution. After remaining relatively constant from 1000 to 1700 c.e., CO2 concentrations began to rise sharply and have increased 30% since pre-industrial times. They are continuing to increase by approximately one-half percent per year.

Additional Information: www.ipcc.ch

Return to Top

E. Where Do Greenhouse Gases Come From?

Greenhouse gas emissions resulting from human activities are substantially increasing the atmospheric levels of the greenhouse gases which include carbon dioxide, methane, halocarbons (HFCs), and nitrous oxide. Carbon dioxide emissions have increased 30% during the past century largely due to fossil fuel combustion which produces the largest amount of CO2 emissions (about 80% of United States GHG emissions and about 87% of California emissions). In California, approximately 43% of the CO2 emissions come from cars and trucks. Methane emissions have doubled in the past 100 years. Over the same period, nitrous oxide levels have risen about 15%. Agriculture is a major source of both methane and nitrous oxide, with additional methane coming primarily from landfills. Halocarbons are another greenhouse gas. Most halocarbon emissions come from their use as refrigerants, solvents, propellant agent, and industrial processes. Manufactured compounds, like HFCs, persist in the atmosphere for long periods of time and have far greater effects at lower concentrations as compared to CO2. Although the amount released of these compounds is small, they are very effective at trapping heat in the atmosphere.

Return to Top

A. What Are The Potential Impacts For California's Water?

Over the past 150 years, monitored mountain glaciers have been shrinking. If glaciers continue to shrink, summer water flows will drop sharply, disrupting a source of water for irrigation and power in many areas that rely on mountain watersheds. This in turn will likely lead to more flooding during the winter and worsen drought conditions. In California's Central Valley, for example, melting snow provides much of the summer water supply; warmer temperatures would cause the snow to melt earlier and thus reduce summer supplies even if rainfall increased during the spring. Instead of increasing the amount of water supply available, the disrupted cycle is likely to cause excess rainfall and run-off, thus causing flooding and overflow of reservoirs which are not equipped to contain such large inflows of water.

The shortage of water in the summer due to runoff changes could worsen drought and increase diversions of rivers in California. This would mean higher cost and further adverse effects downstream. Together with changing temperatures, flows, and the ability of watersheds to assimilate wastes and pollutants, changing runoff patterns could also have the potential to alter water quality significantly. Additionally, sewage systems could be overwhelmed by storm runoff and high tides.

Rising sea levels can cause an increase in the intrusion of salt water into coastal aquifers, contaminating fresh water supplies. Sea level rise could especially affect the Sacramento San Joaquin River Delta, the hub of California's water transfer system. Higher tide levels would pose additional problems to the precarious Delta levee systems with a risk of more inland inundation and the corresponding threat to export water quality.

Return to Top

B. What Are The Potential Impacts For California's Agriculture?

Potential impacts, such as reduced water supply, more severe droughts, more winter floods, and drier growing seasons will affect agriculture (a $26 billion Californian industry in 1997). Many farms especially in the fruit and nut business require long-term investments, making fast adaptation difficult, and could thus experience serious losses if decisions continue to be made with no regard to expected climate changes.

Water is needed year-round, especially for perennial crops. Perennial Crop growers can not shift quickly to new types of cultivars and they need reasonable water supply projections such as several decades for trees and vines. Problems with crops can persist many years if there is an extreme weather or pest-related event. Fruit trees are particularly vulnerable. Too much rain or too little rain can be a problem, as well as pest impacts, too much or too little fog, less frost days, and changes in the timing of the season can all disrupt their market.

In order to better deal with water shortage issues, irrigation practices need to improve, because there is already an increase in salts in the land. Some areas may lose productive capacity in a matter of decades with or without climate change, but climate change could make the problem worse. Even vineyards can be susceptible to fungi because of increased rainfall at the wrong time.

Coastal agriculture is also at risk due to potential impacts of sea level rise. Even if farmers move crops closer to the fog, they may permanently lose agriculture lands to the ocean.

Return to Top

C. What Are The Potential Impacts For California's Fishing Industry?

Studies found that as a result of changes in ocean conditions, the distribution and abundance of major fish stocks will change substantially. Impacts to fisheries related to El Nino/ Southern Oscillation illustrate how climate directly impacts marine fisheries on short term scales. Higher sea surface temperatures in 1997-1998 during the El Nino had a great impact on market squid, California's largest fishery by volume. The California Regional Assessment reports that landings fell to less than 1,000 metric tons in that season, down from a 110,000 tons in the 1996-1997 season. Other unusual events also occurred such as poor salmon returns, a series of plankton blooms, and seabird die-offs.

Return to Top

D. What Are The Potential Impacts For California's Coastline?

With climate changes, recreational facilities and developed coastlines will also be more vulnerable to hurricanes, storm surges, flooding increases. Increasing population growth in coastal areas is a reason for further concern, since these areas could be more vulnerable to climate change impacts. Impacts of expected sea level rise and increased storm surges are numerous. Beachfront homes and harbors as well as wetlands may flood. Sewage systems may be overwhelmed by storm runoff and high tides. Coastal airports are vulnerable to flooding (San Francisco, Oakland and Santa Barbara). Jetties and seawalls may have to be raised and strengthened to protect harbors which are used for shipping, recreation, and tourism.

Return to Top

E. What Are The Potential Impacts For California's Forests?

The California Regional Assessment notes that an increase in the number and extent of areas burned by wildfires in recent years, and modeling results under changing climate conditions suggest that fires may be hotter, move faster, and be more difficult to contain under future climate conditions. The factors which contribute to the risk of catastrophic fires (fuel loads, high temperatures, dry conditions, and wind) are typically present already in summer and fall seasons in California, but can exist at other times of the year, especially in drought conditions. Public safety is an issue as more home and tourism developments on coastal hills and mountains and the foothills and higher elevations in the Sierra Nevada are highly susceptible to catastrophic wild fires.

Other climate impacts affecting forestry are: Higher CO2 concentrations which may increase growth, drought which can kill forests, changes in mineral nutrients, and pest population dynamics. However, more research is needed to understand whether total plant material is expected to increase or decrease in California due to climate changes. Today's models of the Sierra Nevada and North Western California provide contradictory results on this subject.

Return to Top

F. What Are The Potential Impacts For Air Pollution In California?

Projected climate changes will impact the quality of California's air, public health, and environment. Higher temperatures increase the formation of ground level ozone and particulate matter, making it more difficult to meet the health-base air quality standards for these pollutants. Ground-level ozone has been shown to aggravate existing respiratory illnesses such as asthma, reduce lung function, and induce respiratory inflammation. Ambient ozone also reduces agricultural crop yields and impairs ecosystem health.

The particulate matter of most concern - PM10 - has a diameter smaller than 10 micrometers and can easily pass into the lung, contributing to the development of lung tissue damage. PM10 has been implicated in exacerbation of cardiovascular disease, asthma, other respiratory diseases, and associated with increased mortality. Air pollution is also made worse by increases in natural hydrocarbon emissions and evaporative emissions of fuels and solvents which leads to higher levels of ozone and PM10 during hot weather. Warmer temperatures that cause increased use of air conditioners can cause increased air pollutants from power plants and from vehicle operation. In addition, warming, drying, and increased winds could mean hotter, harder-to-control wildfires. These wildfires could result in increased levels of fine particulate matter that could also exceed State and federal standards and harm public health.

Return to Top

G. What Are The Potential Impacts For California's Energy Supply?

California's electricity generation is currently relatively efficient when it comes to emissions of greenhouse gases. The national average for the electricity generation share of total greenhouse gas emissions is approximately 40%, while California electricity accounts for only 16% of statewide emissions. This is in part due to California's significant amount of imported electricity, mild climate, and lack of energy-intensive industry. Over the past two decades, California has developed one of the largest and most diverse renewable electricity generation industries in the world. However, changes in climate of the magnitude predicted by the IPCC would substantially affect electricity generation throughout California and the entire Western States grid, particularly for hydroelectric facilities.

Less snowpack would result in lower levels of hydro generation in the summer and fall seasons due to reduced runoff in those seasons. Additional hydropower may be available during the winter and the spring. However, on balance hydropower is more useful and valuable within the grid mix of generation sources when it is available throughout the peak summer and fall seasons. The Natural gas distribution system may also be damaged because of landslides and fires. Flooding could also impact pipelines, wells and related petroleum extraction equipment. Warmer weather would result in an increased demand for electricity for cooling appliances in homes, and businesses.

Return to Top

H. What Are The Potential Impacts For California's Ecosystems?

The current distribution, abundance, and vitality of species and habitats are strongly dependent on climatic (and microclimatic) conditions. Climate change is expected to result in warmer temperatures year-round, accompanied by substantially wetter winters. Rising sea level will significantly affect coastal wetlands because they are mostly within a few feet of sea level. As the sea rises, these wetlands will move inland. The overall acreage of wetlands will be reduced due to constraints by existing urban development and steeper slopes immediately inland of existing wetlands. Tidal rivers, estuaries, and relatively flat shoreline habitats will be more subject to damage by flooding and erosion. More severe storm surges from the ocean, due to higher sea levels, combined with higher river runoff could significantly increase flood levels by more than the rise in sea level alone. Erosion of beaches would decrease habitat for beach-dependent species, such as seals, shorebirds, and endangered species (for example, snowy plover and least tern). Aquatic habitats are also likely to be significantly affected by climatic changes. Most fish have limits to how hot or cold the water can be before they must either find more hospitable temperatures or die. As temperatures warm, many fish will have to retreat to cooler waters.

Changes in temperature and precipitation patterns would also shift California's current climate zones, and thus habitats associated with these zones, northward by approximately 100 - 400 miles, as well as upwards in elevation by 500-1500 feet. Global climate change would alter the composition, structure and arrangement of the vegetation cover of the state (forest and wildland). Species distribution would move geographically as the climate changes, with forest stands, woodlands and grassland species predicted to move northward and higher in elevation. The entire vegetative community may be affected if non-native invasive species occupy sites and replace native plants. Outbreaks of insects and diseases could compromise forest health and the capability of the forest stands reproduce and to store carbon on a landscape basis. Forest fires are likely to become more frequent and severe if soils become drier. Changes in pest populations could further increase the stress on forests.

Return to Top