A 2011 study projected that the frequency and magnitude of both maximum and minimum temperatures would increase significantly as a result of global warming. According to the
Fifth National Climate Assessment published in 2023, coastal states, including California, Florida, Louisiana, and Texas are experiencing "more significant storms and extreme swings in precipitation".
Wildfires (pink) and smoldering brush in the
Tumbleweed Fire, which burned 1,000 acres of vegetation north of Los Angeles in July 2021 talks about climate change and wildfires at the
North Complex Fire in 2020 Numerous studies have found that climate change is increasing the frequency of large and explosive
wildfires in California in particular. The economic and human health damages of recent fire seasons has been estimated to be as high as $148.5 billion, or roughly 1.5% of California's annual GDP. This damage is mostly a result of smoke-related air pollution. As a consequence of further global warming, it is projected that there will be an increase in risk due to climate-driven wildfires in the coming decades. In addition, due to human fire suppression methods, there is a build of fuels in some ecosystems, making them more vulnerable to wildfires. There is greater risk of fires occurring in denser, drier forests, where historically these fires have occurred in low-density areas. Lastly, with increases in human population, communities have expanded into areas that are at higher risk to wildfire threat, making these same populations more vulnerable to structural damage and death due to wildfires. Since 1990, the average annual number of homes lost to wildfires has increased by 300%. Almost 900,000 of western US residences were in high risk wildfire areas as of 2017 with nearly 35% of wildfires in California starting within these high risk areas. In 2019, after "red flag" warning about the possibility of wildfires was declared in some areas of California, the electricity company "Pacific Gas and Electric (PG&E)" begun to shut down power, for preventing inflammation of trees that touch the electricity lines. Millions can be impacted. The climatic conditions that cause this warning became more frequent because of climate change. If the temperatures keep rising, such power outages could become common. Recent wildfire seasons have broken number of records. The
2018 season became the deadliest and most destructive in the state's history, with 103 people killed and 24,226 buildings damaged or destroyed. The
2020 season became the largest in the state's recorded history in terms of area burned, with more than 4 million acres burned across the state in 9,917 wildfires. Out of six of the biggest fires ever recorded in the state of California, five took place in 2020. In 2017, a study projected that the single largest threat to Los Angeles County hospitals related to climate change is the direct impact of the expected increase in wildfires. In Los Angeles County, 34% of hospitals are located within one mile of fire hazard severity zones. Additionally, one of these hospitals was also deemed in danger of
coastal flooding due to the effects of climate change as concluded by the study. This latter issue was also included and focused on, as the study likewise concluded that this would become a greater hazard as
sea level rise due to increase annual temperatures. In January 2025 Southern California wildfires were deadly and affected millions of people. The two largest fires, the Eaton Fire in Altadena and the Palisades Fire in Pacific Palisades burned over 37,000 acres and killed 31 people. In Altadena, the Eaton Fire killed 19 people. 18 victims lived west of Lake Avenue, a predominately black neighborhood in Altadena. Residents from west Altadena received emergency evacuation orders hours after those in east Altadena, after the fire had already reached those residents' homes. Altadena has long been a culturally diverse area of Los Angeles with long-term homeowners. According to census data, almost 60% of Altadena's population are people of color, and over 75% of Black Altadena residents own their home (which is over double the national rate of Black home ownership). In the Eaton fire, over 9,000 structures burned, with over 6,000 homes lost. Many homes in Altadena have been passed down generationally, and there is fear that there will be climate gentrification as families and elderly move away from the burn scar. These fires in Los Angeles placed thousands under evacuations, with shelters overwhelmed with families, pets, and wildlife. In both the Palisades and Altadena, vast numbers of wildlife were displaced. Larger animals like bears and mountain lions were forced into neighborhoods; new bird species moved into new nests and areas across Los Angeles, while aquatic wildlife such as fish and newts sheltered-in-place. It is unclear about the effects of Monarch Butterflies in the region, who cluster on trees in the region. Studies show that insects and less mobile invertebrates such as aphids, parasitoid wasps, and springtails are essentially gone from the region as wind speeds and the expansion of the fire moved too quickly for them to fly away or find shelter. Smoke is more toxic from urban fires due to what is being burned, which includes automobiles, plastics, metals, rubber, pesticides, paint, carpets, and anything else found in homes. Even in areas outside of the burn scar, smoke and ash will travel up to thousands of miles, depending on weather conditions. Wildfire smoke can make anyone sick, but children, elderly, and people with pre-existing medical conditions such as asthma are more likely to have health problems during and following smoke exposure. During the Los Angeles fires in January 2025, more than 600,000 students had school canceled due to wildfire damage, ash, and smoke. More than 80% of students in Los Angeles Unified School District are in poverty, who were unable to access education, resources, and food due to closures and evacuations. Thousands of students from Altadena and the Pacific Palisades whose schools burned down were not able to be funneled into neighboring districts and schools for many weeks to months, and many entered classrooms that had high student-teacher ratios and were unable to get the academic and emotional support they needed. Wildfires disproportionately affect many different communities of people. The Eaton Fire in Altadena was ignited from sparks on power lines owned by Southern California Edison Power, who failed to shut off power during 100-mile winds. Data shows that power plants are often placed in neighborhoods occupied by people of color and who are low-income, which is reflected by Altadena's racial populations. Children are also disproportionately affected by wildfires, as they are more susceptible to health effects, often have school canceled due to air quality or evacuations, and cannot vote for legislation that affects them and the climate. Elderly and disabled communities are also dramatically affected by health concerns associated with wildfires, and many are unable to evacuate without assistance. People that are low-income often do not have the financial resources to evacuate, and if losing their home, do not have the resources to find new homes, participate in lawsuits, and find personal essentials like clothing and toiletries. Wildfires are linked to climate justice because climate change exacerbates wildfires, and different communities disproportionately suffer due to intersectional identities (including all organisms in ecosystems). The winds generated in the January 2025 Los Angeles fires are a result of the orographic effect occurring on the San Gabriel and Santa Monica Mountain ranges, which is amplified by decreased precipitation leeward side and increased wind on the windward side of the mountains. [1]
Controlled burns Wildfire suppression has resulted in wildfires becoming more severe and common, as dead and untamed brush is used as fuel by wildfires. A study performed in 2023 generated different forms of wildfire management, and built modeling framework that stimulated different wildfire conditions (wind, fuel, moisture, ignitions, growth, suppression, ecology). This simulation found that suppression bias directly influences fire activity and ecological responses in the environment. This is an example of climate injustice as marginalized communities are most affected by wildfires, including wildlife. While laws and regulations in California encourage controlled burns, there are often many environmental reviews and permits required that limit accessibility of performing controlled burns. This prevents many Indigenous tribes from being able to practice their culture, which includes controlled burns for vegetation management, ecological regeneration, and clearing brush to hunt. The combination of fire suppression practices and human-driven climate change have increased the severity of wildfires. A study reviewed socioeconomic patterns that are related to reduced overall health, and health and found that PM2.5 is generated in a variety of industrial settings, including wildfires. Regions with high PM2.5 were correlated with high rates of poverty, housing inequities, linguistic isolation, unemployment, cardiovascular-related emergency department visits, and lower rates of education. Additionally, PM2.5 exposure is linked to health issues including dementia, Altzheimer's, preterm birth, and lung and brain cancer. These health effects and socioeconomic effects are amplified by wildfires and are a form of climate injustice. [i] Fire is a traditional cultural practice for many indigenous communities throughout California. Norton-Smith et al. notes, "The exclusion of fire from landscapes creates a situation of denied access to traditional foods and spiritual practices, puts cultural identity at risk and infringes upon political sovereignty. On a more individual level, the altered forest conditions create social strain for the individuals who hold the most responsibilities to tend to specific places and provide food to the community for subsistence as well as ceremonial purposes." Chapin et al. (2008) found that the greatest wildfire risk is associated in areas where wildfire suppression has occurred.. Fire suppression continues to be an expression of settler colonialism, as well as exacerbating anthropogenic climate change and preventing stewardship with the land.
Drought , which is experiencing its worst drought in 1,200 years, precipitated by
climate change, and is therefore
water rationing Research conducted in 2022 found that, through 1,200 years of data available in the region, the
ongoing drought in the southwestern United States was the most severe drought ever recorded in the region. In the absence of climate change, the drought would have likely ended in 2005, which was categorized as a wet year. The flow of the Colorado River, supplying water to seven states, had "[shrunk] to the lowest two-year average in more than a century". Temperature rise caused by climate change has been estimated to be a considerable contributor to the severity of the drought, with 88% of the western United States being categorized as drought-stricken, as
anthropogenic warming substantially increases the likelihood of California droughts.'''''' According to the
NOAA Drought Task Force report of 2014, the drought is not part of a long-term change in precipitation and was a symptom of the natural variability, although the record-high temperature that accompanied the recent drought may have been amplified due to human-induced global warming. If the temperature rise continues, the drought will become worse. A water due to low
snowpack prompted Californian Governor
Jerry Brown to issue a series of stringent mandatory water restrictions on April 1, 2015. In February 2014, the effects of the California drought caused the
California Department of Water Resources to develop plans for a temporary reduction of water allocations to farmland by up to 50% at the time. During that period, California's 38 million residents experienced 13 consecutive months of drought. This is particularly an issue for the state's 44.7 billion dollar agricultural industry, which produces nearly half of all American-grown fruits, nuts, and vegetables. However, a study published in 2016 found that the net effect of climate change has made agricultural droughts less likely, with the authors stating that "Our results indicate that the current severe impacts of drought on California's agricultural sector, its forests, and other plant ecosystems have not been substantially caused by long-term climate change." As California continues to experience droughts, different communities are affected in disproportionate ways. UC Davis found that California's surface water costs triple during droughts. Furthermore, the cost of water varies if water systems rely on groundwater because treatment and delivery costs are relatively low. The Public Policy Institute of California notes that average water bills vary considerably across urban water systems, there are no guideline for determining if water bills are too high, and that public water agencies are restricted in assisting low-income households with water bills. Thus, people in different socioeconomic groups are impacted differently from rising water costs. Racial disparities have also been linked to not having access to water. San Francisco and Los Angeles are ranked as some of the highest metropolitan areas in the United States with the highest percentages of households lacking complete plumbing. The Journalist's Resource from Harvard Kennedy School introduces the idea of "plumbing poverty," where infrastructure provision is clearly racialized and historically produced in the United States. Research conducted by Carolina Balazs and Isha Ray and published in the American Journal of Public Health (April 2014) found that from 2005 to 2010, groundwater pumped from wells in the San Joaquin Valley have been chronically contaminated with arsenic, levels above the accepted amount set by the World Health Organization (WHO). Exposure to arsenic can cause long-term health effects such as skin, lung, and bladder cancer, cardiovascular disease, neurological issues, or short-term effects such as nausea, vommiting, and diarrhea. These policies were designed to deprive residents of drinking water resources. The 1973 Tulare County General Plan stated that "non-viable communities would, as a consequence of withholding major public facilities such as sewer and water systems, enter a process of long term, natural decline as residents depart for improved opportunities in nearby communities." This is an example of systematic environmental injustice, where essential services in Tulare County were intentionally poisoning residents, which also contaminated ecosystems and damaged plants, animals, and soil health.
Atmospheric rivers and megafloods Atmospheric rivers are powerful weather events that pick-up moisture from the ocean and transport water across the land and are responsible for half of California's annual precipitation events. They commonly cause flooding, landslides, power outages, and damage to structures. A study published in
Science Advances in 2022 stated that climate-caused changes in
atmospheric rivers affecting California had already doubled the likelihood of
megafloods since 1920—which can involve of rain and/or melted snow in the mountains per month, or of snow in the
Sierra Nevada—and runoff in a future extreme storm scenario is predicted to be 200 to 400% greater than historical values in the Sierra Nevada. Atmospheric rivers are crucial for building the state's snowpack and refilling reservoirs and groundwater but often cause significant damage to communities. With global warming and climate change, warmer atmospheres hold more vapor, making atmospheric rivers more intense and extreme. Wind is commonly associated with atmospheric rivers, and typically cause damage to homes and buildings, uproot trees and telephone poles, cause power outages, and injure people from flying debris. Effects from atmospheric rivers have varying effects on different communities and people. People who are low income may live in more severely affected areas, have less access to resources for repairs, and be more exposed to debris and active hazards.
Forest management Drought-surviving
sugar pines around Lake Tahoe have been found among 129 million trees in California killed between 2012 and 2016 by drought and
bark beetles. Thousands of seedlings descended from these trees are being planted south-facing slopes on the lake basin's north side with the hope that they carry
genes that make them more resilient to drought, waning snowpack and other effects of global warming in the forests of
Sierra Nevada. The 2022 IPCC report on climate change and mitigation suggests that California land management needs to consider the changing climate when updating their forest management practices, especially when considering fire management. In forests of the southwestern United States, climate change and fire exclusion management practices have led to increased severity of wildfires. Prescribed burning is an effective fire management tool that, when utilized in savanna ecosystems early in the dry season, has also been shown to reduce emissions. The results on whether or not
prescribed burning also reduces emissions in forests are inconclusive and needing further study.
Agriculture Extended periods of higher temperatures are expected to increase
navel orangeworm reproduction, resulting in increased insect damage to
almond,
walnut, and
pistachio crops. California has over 76,000 farms and ranches and is one of the largest and most diverse agricultural industries in the United States. Climate change has increased global warming, which has begun (and will continue) to reduce winter chill hours. It is projected that by 2050, yields of avocados will decrease by 40 percent, and yields of almonds, table grapes, oranges, and walnuts will decrease by 20 percent. Furthermore, climate change reduces the amount of available water for agriculture in both plant and animal cultivation. Soil health and nutrients decrease as soil erosion is amplified by intense winds and rains, and moisture is reduced during droughts. Already, California has lost over one million acres of available agricultural land between 1984 to 2010, and another one million acres are projected to be lost by 2030 from climate change. Millions of people rely on Californian agriculture for access to citrus, fruits, nuts, cattle, and vegetables. It is reported that California produces half of the United States' vegetables, and over three-quarters the country's fruits and nuts. This industry generates billions of dollars annually and employs over 900,000 people, all of which is vital to California's economy. Furthermore, increased temperatures from human driven climate change expand insect life cycles and breeding seasons, leading to more offspring each year. In each generation of offspring, common agricultural pests become more resistant to crops, pesticides, and temperatures. Extreme weather events help distribute pests, and elevated carbon dioxide in the atmosphere weaken plant defenses. Pesticide use is known as one of the most prominent and explicit cases of environmental racism in the United States. Hundreds of thousands of farmworkers, the majority who are Mexican immigrants or from other Latino communities, are poisoned by distributing pesticides and harvesting or transporting those crops. Additionally, their families are poisoned from proximity to pesticides and groundwater and soil contamination. In California, 200 million pounds of pesticides are applied annually and more than half of pesticide use occurs in the eight lowest-income counties. As climate change increases insects and pests, pesticides become more important to maintain healthy crop harvests and support farms. However, many pests are adapting to less harsh chemicals and pesticides, pushing towards more severe chemical usage on farms. The impact of climate change on precipitation in California can lead to the occurrence of severe drought. During droughts in California, farmers leave land
fallow. In 2014 drought season, 430,000 acres of farmland were left to fallow. Farmers anticipate they will fallow a similar number of acres of farmland in 2022.
Fisheries impact Ocean heat waves since 2013 have delayed three
Dungeness crab seasons, due to harmful
algal blooms that contaminate crab meat.
Hydrology and dams Changes in hydrology have occurred as decreased snowpack, especially at lower elevations, melts and has spring run-off earlier in the year. Run-off in the late spring decreases, as snow melts at the end of winter and early spring, which increases river and stream temperatures and raises variability in streamflow. These changes in hydrology and the river system extend the period of flooding and run-off, as well as increasing the grain sizes that can be transported in the channel, which destroys plants and crops. Furthermore, it erodes the river and banks at a higher rate for longer periods of time (decreasing available land and changing the river's natural erosion patterns). The rate of snowpack melting has increased as a result of climate change, as the average global temperature has begun to melt snowpack earlier in the year and not become cold enough for precipitation in the form of snow. California has a long history of dams, most notably the Hoover Dam, Oroville Dam, St, Francis Dam, and Klamath River dams. There were originally a total of six dams on the Klamath river, now only two non-hydroelectric dams remain and are part of the Klamath River watershed. These dams were in place to divert water for irrigation purposes. Recent efforts removed four lower hydroelectric dams (Copco No. 1, Copco No. 2, Iron Gate Dam, and J.C. Boyle Dam) as part of the largest dam removal effort. This removal was part of an effort to improve water quality and fish migration in the river. Dams impact salmon's ability to migrate upstream to spawn, leading to mass fish die-offs. Furthermore, stagnant water created by dams lead to increased water temperature and sediment accumulation, which is ideal for algal blooms. Algal blooms produce toxins that are harmful to plants, animals, and humans by creating "dead zones" that deplete oxygen in the water and block sunlight from reaching aquatic plants and animals. Indigenous tribes actively rely on the Klamath river to practice culture. Salmon and trout struggled to survive and reproduce prior to the dam removal due to unhealthy water conditions. Indigenous tribes rely on salmon for food and to practice traditional fishing methods, which allows them to practice their culture. Furthermore, the removal of these dams have allowed traditional indigenous peoples to descend from the headwaters of the Klamath River in Southern Oregon to the mouth of the Klamath in Northern California, home to the Yurok Tribe. == Sea level rise ==