Climate change involves natural and man-made changes to weather patterns that occur over millions of years or over multiple decades.
In the past 150 years, human industrial activity has accelerated the rate of change in the climate due to the increase in greenhouse gases (carbon dioxide, methane, and nitrous oxide). Scientific studies describing this climate change continue to be produced and its expected impacts continue to be assessed.
Climate change is having “a significant and measurable impact” on California’s environment, based on the analysis of 36 indicators of climate change and its effects, according to a 2013 report by the Office of Environmental Health Hazard Assessment, Indicators of Climate Change in California.
The indicators showed how that climate change is occurring from the Pacific Coast to the Central Valley to the Sierra Nevada, with decreasing spring snowmelt runoff, rising sea levels, shrinking glaciers, increasing wildfires, warming lakes and ocean waters, and the gradual migration of many plants and animals to higher elevations.
Already, California is confronting rising demand for water and diminishing supplies. At the same time, the state’s water infrastructure such as levees is aging and in disrepair—conditions expected to be made worse by climate change.
Climate Change in California Overview
Facts and figures for the potential impact of climate change continue to be unveiled. Recent reports by the California EPA and the CEC and CNRA have concluded:
- Precipitation patterns are changing, with more rain, less snow and shrinking glaciers in the Sierra Nevada (the primary source of much of California’s fresh water supplies)
- Less snowpack and earlier springtime melting is reducing hydropower capacity
- The Sacramento San Joaquin Delta—California’s water hub—is sinking, putting levees at risk for failure and cities such as Sacramento at risk for flooding
- Rising sea levels will also worsen coastal flooding and possibly swamp key infrastructure such as airports and ports
- Hotter temperatures will also lead to more wildfires of increased intensity; already of more than half of California’s largest wildfires have been in the last decade
- Dry weather will lead to more tree deaths and altered vegetation patterns, with some plants moving to higher ground
- More wildlife is also expected to change habitat, with some already migrating to higher ground
- Hotter weather will also likely lead to more potentially lethal heat waves and related water shortages and droughts
- Oceans and lakes are likely to see their average water temperatures rise (Lake Tahoe has risen by nearly 1 degree in the past three decades)
- Shortened chill periods in winter needed for growing fruits and nuts
- Native freshwater fish are particularly vulnerable to climate change and a 2013 University of California, Davis study found 82 percent of California native fish species are at risk of extinction
In a 2017 report, Anthropogenic Warming Impacts on California Snowpack During Drought, researchers with the Department of Atmospheric and Oceanic Sciences at University of California, Los Angeles, found that anthropogenic warming reduced average snowpack levels by 25 percent and that under a severe drought scenario, “further snowpack declines of 60 percent to 85 percent are expected, depending on emissions scenario.”
Climate Change Next Steps
The focus on climate change has prompted many in the water community to call for a comprehensive response on the part of state, federal and local officials.
Many water agencies are already including climate change impacts in their long-term planning, factoring in a need for increased conservation, groundwater banking and new surface storage projects. Also under consideration by some water districts and agencies are desalination and importing water from other groundwater basins.
In 2006, then California Gov. Arnold Schwarzenegger signed into law Assembly Bill 32, making the state the first in the nation to impose a cap on all greenhouse gas emissions. The law aims to reduce the state’s emissions of carbon dioxide and other greenhouse gases by an estimated 25 percent by 2020.
In 2016, Gov. Jerry Brown signed legislation that requires California’s emissions fall to 40 percent below 1990 levels by 2030. Brown followed that up in 2017 by signing legislation to extend AB 32, which requires oil refineries, power plants, food processors and other facilities to purchase permits to release carbon dioxide into the atmosphere.
Still, some are skeptical of proposals to limit emissions of greenhouse gases and the potential economic impacts of such actions. Political debate has centered on the merits of the science used to justify various claims. Meanwhile, some in the business community say efforts to enact greenhouse gas emission reductions in California through arbitrary means are counterproductive, given the scale of global emissions and the fact that companies could move their operations to places without emissions caps.
While the state works to balance the needs of multiple interests, climate change and population growth pose additional future challenges.
The state’s population of about 39.5 million in 2017 was expected to reach 45.8 million by 2036, according to the California Department of Finance. Climate change adds complexities and questions to this growth and related environmental impacts in the future.
These remain key issues as state experts work to determine how to best incorporate a changing climate into water management planning, including flood planning due to a sea level rise, peak flow changes and a reduced snow pack.