Projected average annual area burned by wildfire in California for 2035–2064 and 2070–2099. Data: Westerling, 2018. Graphic: CNRA

By Tony Barboza , Bettina Boxall, and Rosanna Xia
27 August 2018

(Los Angeles Times) – Heat waves will grow more severe and persistent, shortening the lives of thousands of Californians. Wildfires will burn more of the state’s forests. The ocean will rise higher and faster, exposing California to billions in damage along the coast.

These are some of the threats California will face from climate change in coming decades, according to a new statewide assessment released Monday by the California Natural Resources Agency.

The projections come as Californians contend with destructive wildfires, brutal heat spells, and record ocean temperatures that scientists say have the fingerprints of global warming.

“This year has been kind of a harbinger of potential problems to come,” said Daniel Cayan, a climate researcher at the Scripps Institution of Oceanography and one of the scientists coordinating the report. “The number of extremes that we’ve seen is consistent with what model projections are pointing to, and they’re giving us an example of what we need to prepare for.”

State leaders vowed to act on the research, even as the Trump administration moves to unravel climate change regulations and allow more pollution from cars, trucks and coal-fired power plants.

“In California, facts and science still matter,” Gov. Jerry Brown said in a statement. “These findings are profoundly serious and will continue to guide us as we confront the apocalyptic threat of irreversible climate change.”

The state’s assessment draws on the latest science, including more than 40 new peer-reviewed studies, to project the effects of the continued rise in greenhouse gases on California’s weather, water, ecosystems and people and offer guidance on how officials across the state might adapt.

Flood risk at Seal Beach, California. Scientists modeled a 100-year flood — a severe but realistic storm that has a 1 in 100 chance of occurring in any given year this century — based on the latest climate science and sea level rise projections. Graphic: Los Angeles Times

It’s the fourth such report since 2006, when Gov. Arnold Schwarzenegger ordered a climate change assessment as precursor to the Global Warming Solutions Act, the pioneering law California adopted that year to cut greenhouse gas emissions to 1990 levels.

This latest one for the first time scales down global climate models to project climate’s effect at the regional level or smaller. That approach is intended to provide local officials on the ground with more relevant, community-level information they can use to prepare.

“The difference between the San Joaquin Valley and the nearby coastal or Sierra Nevada mountains is enormous, so we have to have ways to unpack the large-scale global model calculations,” Cayan said. [more]

Climate change will be deadlier, more destructive and costlier for California than previously believed, state warns

Projected daily maximum sea level at La Jolla constructed from the eight hourly simulations that conform to RCP 4.5 and RCP 8.5 simulations. Envelopes of 50th-95th percentile daily maximum of RCP 4.5 and RCP 8.5 projections are shown in light blue and light red. The maximum annual value from 99.9 percentile RCP 4.5 and RCP 8.5 projections are shown as solid blue and solid red lines. Maximum observed historical sea level at La Jolla is shown as blue inverted triangle. Graphic: CNRA

By Robert Monroe
27 August 2018   

SACRAMENTO (UCSD) – The State of California today released California’s Fourth Climate Change Assessment, which details new information on the impacts of climate change and provides planning tools to support the state’s response.

Among the assessment’s warnings are that two-thirds of Southern California’s beaches could completely disappear and the average area burned by wildfires could nearly double by 2100. Dan Cayan, a climate scientist at Scripps Institution of Oceanography at the University of California San Diego, served as editor-in-chief of the assessment and researchers from Scripps and California Sea Grant contributed to several of its technical and summary reports.

"To prepare for climate changes and to avoid possible catastrophic impacts, California needs a massive platter of scientific information,” Cayan said. “The Assessment supplies such information in finer spatial detail and with greater attention to episodic events, illustrating an extensive set of changes that may confront us over the next several decades."

The compilation of original climate research includes 44 technical reports and 13 summary reports on climate change impacts to help ready the state for a future punctuated by severe wildfires, more frequent and longer droughts, rising sea levels, increased flooding, coastal erosion and extreme heat events. The peer-reviewed research translates global models into scaled-down, regionally-relevant reports to fill information gaps and support decisions at the local, regional and state levels.

“In California, facts and science still matter,” said Governor Edmund G. Brown Jr. “These findings are profoundly serious and will continue to guide us as we confront the apocalyptic threat of irreversible climate change.”

Projected percent changes in average annual California household electricity consumption in 2080-2099 for RCP 8.5 relative to a 2000-2015 baseline. Data: Auffhammer, 2018. Graphic: CNRA

California has completed three prior Climate Change Assessments. Since the release of California’s Third Climate Change Assessment in 2012, the state has experienced several of the most extreme natural events in its recorded history, including a severe five-year drought, an unprecedented tree mortality crisis, damaging floods driven by atmospheric rivers, and increasingly large and destructive wildfires.

The Fourth Assessment suggests these events will worsen in the future. Among the key findings:

  • Wildfire: Climate change will make forests more susceptible to extreme wildfires. By the year 2100, if greenhouse gas emissions continue to rise, one study found that the average area burned by wildfires would increase 77 percent and the frequency of extreme wildfires burning more than 25,000 acres would increase by nearly 50 percent. In the areas that have the highest fire risk, the cost of wildfire insurance is estimated to rise by 18 percent by 2055. Additionally, the percentage of property insured in California would decrease.
  • Sea-Level Rise: Under mid to high sea-level rise scenarios, up to 67 percent of Southern California beaches may completely erode by 2100 without large-scale human interventions. Statewide damages could reach nearly $17.9 billion from inundation of residential and commercial buildings if sea-level rise reaches 20 inches, which is within range of mid-century projections. A 100-year coastal flood, on top of this level of sea-level rise, would almost double the cost of damages. Updated modeling can help local planners analyze vulnerabilities in their area.
  • Energy: Higher temperatures will increase annual electricity demand for homes, primarily for use of air conditioning units. High demand is projected in inland regions and Southern California. More moderate increases are projected in cooler coastal areas. Increases in peak hourly demand during the hot months of the year could be more pronounced. This is a critical finding for California’s electric system, because generating capacity must match peak electricity demand.
  • Extreme Heat Events and Impacts on Public Health: Heat-related illnesses and deaths are projected to worsen drastically throughout the state. By mid-century, the Central Valley is projected to experience heat waves that average two weeks longer than those today, and the hot spells could occur four to 10 times more often in the Northern Sierra region. A new California Heat Assessment Tool (CHAT) could support public health departments as they work to reduce heat-related deaths and illnesses.

The latest reports also detail the unique and disproportionate climate threats to vulnerable communities and tribal communities, with a focus on working collaboratively with these communities on research and solutions for resilience.

In addition, a report set for release in early September will highlight how California can better integrate climate impacts in design processes for critical infrastructure. The report by a working group established by AB 2800 (Quirk) of 2016 reflects the expertise of multiple scientific and engineering disciplines to help design and construct infrastructure to withstand higher temperatures, more frequent and intense storms, drought, wildfires and sea-level rise.

To access Fourth Assessment technical reports, summary reports, online tools, climate projects and data, and other resources and information developed as part of California’s Fourth Climate Change Assessment, please visit

Recent trends of California statewide natural gas demand for the residential sector (blue line) and Heating Degree Days (HDDs, red line). The lines show an overall decline in HDDs and natural gas consumption for the residential sector. Data Source: ARB Fuel Combustion Data; NOAA HDD Data. Graphic: CNRA

California will convene the Global Climate Action Summit in San Francisco next month. At the summit, representatives from subnational governments, businesses and civil society will showcase the surge of climate action around the world, and make the case that even more must be done.

Adapted from California Natural Resources Agency release.


California Releases New Climate Science, Planning Tools to Prepare for Climate Change Impacts



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