Climate in LA / Climate Forecast

This page is about Los Angeles’ changing climate.

1.0 LA’s Past and Present Climate

1.1 What is LA’s climate changing from?

1.2 What is LA’s climate changing to?

1.3 LA’s current climate is going away.

2.0 Climate Forecast for LA

2.1 How hot will it get in LA?

2.2 This is how LA’s climate is changing.

2.3 This is why LA is warming differently in three different locations.

1.0 LA’s Past, Present and Emerging Climate

Climate is the usual weather over a long period of time. Climate is different depending where you are on the globe.

For millions of years, Earth has had roughly 16 general flavors of climate, the same climates we’ve had until the 2000s and 2010s.

These climates are changing noticeably now. Some are changing faster than others. What kind of climate does LA thrive in now, and what kind of climate is LA changing to?

1.1 The longtime balmy climate of Los Angeles has a name. It’s what LA’s climate is changing from.

LA is the crowded, lively city it is largely because it has one of the most comfortable climates in the world. “Hot Summer Mediterranean” is LA’s scientific climate designation. This sub-type of Dry Subtropical Climate (one of the 16 general climates) has warm, sometimes hot, dry summers and mild, rainy winters.

The geography of the City of LA sprawls into the neighboring “Cool/Warm Mediterranean” climate of the LA foothills and the “Semi-Arid” climate of the Baldwin Hills and the Port of Los Angeles on the coast.

Long before people, the region that is now the Los Angeles Basin has had the same pleasant Mediterranean climate for at least 50,000 years. Go back over the most recent 500+ centuries, and the highest summertime temp at future Dodger Stadium ranged between the mid 70˚s to mid 80˚s, with the temp rarely pushing past 90.˚ Just like in the 1990s. Until the climate started to noticeably change.

en.wikipedia.org/wiki/Köppen_climate_classification | en.wikipedia.org/wiki/Climate_of_Los_Angeles

Journal Paper: Holden, Anna,. et al. A 50,000 year insect record from Rancho La Brea, Southern California: Insights into past climate and fossil deposition. Quaternary Science Reviews, 01 May 2017.

1.2 The climate in Los Angeles is changing, but what is it changing to?

A “Dry Whiplash” kind of climate describes LA’s emerging new climate regime. LA’s climate is quickening toward longer periods of total drought. Summertimes will have temps in 110s and 120s. Very hot weather will overtake much of what was LA’s predictably pleasant Fall. The whiplash term comes from University of California researchers describing LA’s surprisingly quick switches between many years of extreme drought and a few weeks of super-voluminous rainstorms …then back to drought again.

Note: LocalClimate.org’s “Dry Whiplash climate” description derives from California’s Fourth Climate Assessment 2018

1.3 Soon, in the late 2040s, LA’s dreamy sweet climate will be an epoch of the past.

The time when LA’s climate will have completely changed is the city’s time of “climate departure.”

“Climate departure” is a kind of geo-temporal tipping point, or point of no return.

For Los Angeles, time of climate departure will be around the year 2048. This is when people in Los Angeles will never again enjoy the area’s comfortable Mediterranean climate. Instead, the LA region will exist in some brand new climate class, with its own set of patterns and characteristics.

In 2018, United Nations (UN) scientists made a shocking, historic warning: Devastating changes in climate will begin to manifest over the next few decades. The changes are happening in real time with the currently growing pace of carbon emissions.

UN scientists estimate that if, by sometime in the 2030s, people have cut dramatically back on burning carbon fuels, a long-term climate apocalypse can be avoided. At least for a while.

In a world with almost no new carbon added to the already warming atmosphere, eventually, the heat can dissipate.

It is still possible, in the 2100s, for droughts to become less severe. Rain and water supplies can become more reliable, and people can consistently grow food outdoors.

Journal Paper: The projected timing of climate departure from recent variability. Mora, Camilo et al (2013). Nature. 502. 183-187. 10.1038/nature12540. 

Note: Time of Climate Departure is “the time after which all future years are predicted to be warmer than any year in the historical record [1865-2005].” 

Global Communication: The historic series of United Nations warnings about carbon emissions and the climate, beginning in 2018.

2.0 This is the Climate Change Forecast for Los Angeles, California.

The usual weather (the climate) of Los Angeles has been changing over the past several decades, and the change has been accelerating. Fifteen of LA’s 20 hottest years have all occurred during the 2000s and 2010s. Going forward, Angelinos will want to know something about LA’s trending climate situation.

2.1 So, the global climate is warming. But what about right here in LA? How hot is it supposed to get?

A toasty 123˚ is the highest temp projected for Los Angeles (in LA’s Woodland Hills neighborhood) in upcoming decades – because of people’s currently increasing use of carbon-fired energy.

during the 2010s, LA had its warmest Summers on record. Recent years have brought record days of heat. People in LA’s Woodland Hills experienced a high temp of 117˚ in LA’s 2018 heatwave.

The highest heat projected for Los Angeles during this century include 118˚ in Downtown LA, 115˚ in Hollywood 113˚ at the UCLA campus. Temps like these in the 110s˚ will happen more often, beginning in the 2040s and onward.

During a heatwave in September 2018, Downtown LA had it’s highest temp so far: 113.˚ Compare this to the 82˚ that is Downtown LA’s usual July high temp.

Scientists: Cal-Adapt (Geospatial Innovation Facility, University of California, Berkeley).   Method: CalAdapt Data Visualization Tool for Projections of  Extreme Heat under High Emissions Scenario 8.5 (“Business as Usual” /  “Growing Pace,” where Emissions continue to rise strongly through 2050 and plateau around 2099).   Data: LOCA Downscaled Climate Projections (Scripps Institution of Oceanography), Gridded Historical Observed Meteorological and Hydrological Data (University of Colorado, Boulder).  

Official Records: National Weather Service (NWS) and National Oceanic and Atmospheric Administration (NOAA) Climate Data for Los Angeles (USC Downtown campus), 1981 – 2010 averages   

Note: All LocalClimate.org temperature readings in the U.S. are shown in Fahrenheit F˚ degrees. Also Note: Daily High Temps (aka Daytime High Temps) are the highest temp reached on a given day, usually occurring in the late afternoon. 

2.2 These graphic details show how quickly (and intensely) Los Angeles’s climate is changing.

No doubt it’s way scary, but people just really want to know what to expect from their local climate.

2.2.1 Los Angeles is trending quickly toward much longer, ever scorchier Summers.

In the 2070s, 2080s, and 2090s, usual daily high temps during LA’s new Super Summer will range from the 90˚s to the high 110s.˚ 

The 2020s – 2040s & 2070s – 2090s timelines here show LA’s emerging new heat season. Atmospheric scientists are calling this extended period of high heat a “Super Summer.”

Away from LA’s Pacific Coast, heat is becoming more extreme, coming more often, and lasting longer.

In recent decades, inland valleys of the LA region have been reaching temps above 90˚ during two months of the year. In the 2070s thru the 2090s, Los Angeles will have daily high temps above 90˚ during five months of the year.

Scientists: Cal-Adapt (Geospatial Innovation Facility, University of California, Berkeley).   Method: CalAdapt Data Visualization Tool for Projections of  Extreme Heat under High Emissions Scenario 8.5 (“Business as Usual” /  “Growing Pace,” where Emissions continue to rise strongly through 2050 and plateau around 2099).   Data: LOCA Downscaled Climate Projections (Scripps Institution of Oceanography), Gridded Historical Observed Meteorological and Hydrological Data (University of Colorado, Boulder).  

State Govt Report: Los Angeles Summary Report. California’s Fourth Climate Change Assessment (2018)  Hall, Alex; Berg, Neil; Reich, Katharine. (University of California, Los Angeles)  Publication number: SUM-CCCA4-2018-007

2.2.2 The new “Super Summer” or “Heat Season” in LA is essentially a series of regular heatwaves merging into one very long, tenacious heatwave.

The 2070s thru 2090s timeline here shows a greatly extended heat season in LA.

Heatwaves are arriving earlier in the Summer and persisting further into the Fall. What used to be one or two occasionally hot days is often now a three or four day heatwave. Late-Summer / early Fall heat waves are merging together for several months of nearly uninterrupted high heat. As time goes on, heatwaves will be considered usual weather.

Scientists: Cal-Adapt (Geospatial Innovation Facility, University of California, Berkeley).   Method: CalAdapt Data Visualization Tool for Projections of  Extreme Heat under High Emissions Scenario 8.5 (“Business as Usual” /  “Growing Pace,” where Emissions continue to rise strongly through 2050 and plateau around 2099).   Data: LOCA Downscaled Climate Projections (Scripps Institution of Oceanography), Gridded Historical Observed Meteorological and Hydrological Data (University of Colorado, Boulder).  

Federal Govt Report: The Third National Climate Assessment (2014): Climate Change Impacts in the United States, Chapter 20: Southwest   [Garfin, G., G. Franco, H. Blanco, A. Comrie, P. Gonzalez, T. Piechota, R. Smyth, and R. Waskom] U.S. Global Change Research Program, pp. 462-486.,  doi:10.7930/J08G8HMN.

a huge crowd of joyous people out in the bright sun, waving at the camera

We’ll change when we do stuff: In the coming decades, community events like this late-September run/walk will have to be scheduled around LA’s ever-lengthening heatwave season. Or folks may want to walk/run after midnight, when temps are more exercise-friendly. Photo by Homeboy 5K.

2.2.3 LA has already been getting warmer. Now it’ll be getting hotter. And hotter.

This is LA heating up: Los Angeles’ annual average high temp is steadily rising. At the current rate of carbon emissions and atmospheric warming, the annual high temp in LA will go past 100˚ sometime in the 2100s. Note these “average annual temps” are determined not only from the high temps each day in the summer, but also during winter months.

​To see long-term trends in the changing atmosphere, and to account for the variability of weather from year to year, atmospheric scientists prefer looking at climate data over a 30-year span. But here, even at 10-year intervals, a steady warming trend blanketed the LA area. Temps in Los Angeles have already been and will keep on rising.

Scientists: Cal-Adapt (Geospatial Innovation Facility, University of California, Berkeley).  Method: CalAdapt Data Visualization Tool for Projections of  Extreme Heat under High Emissions Scenario 8.5 (Growing Pace / Business as Usual scenario) where Emissions continue to rise strongly through 2050 and plateau around 2100), and Low Emissions Scenario 4.5 (Quickly Reduced / Carbon Mitigation scenario) where emissions peak around 2040, then decline.)  Data: LOCA Downscaled Climate Projections (Scripps Institution of Oceanography), Gridded Historical Observed Meteorological and Hydrological Data (University of Colorado, Boulder). 

Note: The Annual Average High Temp is the sum of the high temps of each day of the year, divided by 365. Even the high temp of each Wintertime day is part of the average. 

2.2.4 LA’s easygoing seasonal rain pattern is changing into a frustrating pendulum of moisture extremes.

kids in raincoats playing with a shopping cart in a flooded parking lot

So far, rainfall in Los Angeles is not changing much in terms of amount, but in when and how it rains. 

Already, Angelinos are experiencing lengthy droughts partially extinguished by waves of brutal rainstorms.  All the rain that would have fallen on Los Angeles over the last several months (or even several years) finally comes – all within a very intense several days.

Photo: Associated Press

Journal Paper: Swain, D. L., B. Langenbrunner, J. D. Neelin, and A. Hall, “Increasing precipitation volatility in 21st-century-California,” Nature Climate Change, doi: 10.1038/s41558-018-0140-y, 2018.

2.3 Something is making the climate in Los Angeles change differently in some parts of the city than others.

​The usual weather (climate) across the sprawling Los Angeles landscape is like real estate; it’s all about location.

LA’s number of hot days each year depends on how close one is to the ocean coast, or to the inland desert. Or, whether you’re up in the hills or down in the Valley. Differences in geography, even just within the city limits, makes a big difference in how warm it gets and for how long.

The cold Pacific Ocean water cools the atmosphere above it – including the air several miles inland from the coast. Los Angeles International Airport (LAX) is situated on the coast, so temps go past 90˚ only a few days each year. LAX will stay relatively cool (relative to inland areas of LA) most of the time until the 2050s.

The San Fernando Valley is blocked by hills and sits well enough inland that it hardly benefits from the ocean’s cooling influence.  Summer temps here tend to run several degrees warmer than other parts of the city, and people experience much more time in warmth.

By the 2050s, under the “Growing Pace” carbon emissions scenario, Northridge’s number of days each year with temps over 90˚ will double from those of the 1990s – from 64 days to 127 days. 

Hollywood doesn’t get quite as baked as the San Fernando Valley, but it’s already increasing number of hot days will likewise surge. Two weeks above 90˚ now, four weeks in the 2050s, and two months in the 2090s …this is a quadrupling of hot days each year within the period of an average person’s lifetime.

Scientists: Cal-Adapt (Geospatial Innovation Facility, University of California, Berkeley).  Method: CalAdapt Data Visualization Tool for Projections of  Extreme Heat under High Emissions Scenario 8.5 (Growing Pace / Business as Usual scenario) where Emissions continue to rise strongly through 2050 and plateau around 2100), and Low Emissions Scenario 4.5 (Quickly Reduced / Carbon Mitigation scenario) where emissions peak around 2040, then decline.)  Data: LOCA Downscaled Climate Projections (Scripps Institution of Oceanography), Gridded Historical Observed Meteorological and Hydrological Data (University of Colorado, Boulder). 


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