17.7: Detailed Figure Descriptions

Detailed Figure Descriptions

17.1  Polygonal dried mud cracks

Low water levels at Nicasio Reservoir in Marin County during 2021 during severe drought conditions. Baked-dry polygonal mudcracks lie in land that should be under significant water. This period reflected part of recent drought cycles, and though such reservoirs recover, they will also inevitably drain again as California water demand, and out of control population growth, far exceeds the ability of precipitation to provide for the state in the way it has in the past.

17.1.1 A diagram of solar radiation and energy inputs and outputs

Solar energy imbalance created when greenhouse gases act to trap a portion of solar radiation that would otherwise escape to space and cool Earth. Includes incoming solar radiation, some of which is reflected immediately by high clouds, some of which reaches the ground and is absorbed, and some of which is reflected by ice on land and sea. The flux of energy returns to space, and in normal conditions, the incoming and outgoing energies would be more or less in balance. Today, however, greenhouse gases are stimulated by the infrared radiation emitting from the warmed Earth, and these greenhouse gases therefore return some of that energy back toward Earth, leading to an imbalance.

Solar radiation inputs include absorbed radiation on continents and oceans, minus reflected radiation from clouds and sea ice. Energy absorbed on Earth is then dissipated via "infrared radiation emitted by the surface," which then may interact with anthropogenic gases and be "absorbed and reemitted by greenhouses gases: carbon dioxide, methane, water vapor, nitrous oxide, and others."

17.2.1 A stand of Bristlecone pines growing on pale-white Reed Dolomite

A stand of long-lived Bristlecone pines growing on Reed Dolomite in the White Mountains, CA. The stand of trees grows almost entirely on the white Reed Dolomite, and very sparsely on any other formations visible (probably the early Cambrian Deep Springs or Campito Mountain formations). The soil has a variety of healthy brush growing on it, most plants do not thrive on dolomitic soils; however, Bristlecones have evolved to exploit the opportunity of this less-used substrate, perhaps because of the lessened competition with other faster-growing plans. Many of these Bristlecones are over four thousand years old.

17.2.2 Snow-covered carbonate soil hosting a number of Bristlecone pines

A Bristlecone pine (Pinus longaeva) from the White Mountains, CA, with the characteristic barren, twisting corkscrew shape of the trunk, adorned with sparse green leaves. Little of the tree has foliage; nonetheless, these trees are still alive and, in fact, provide a record of growth that proves very useful for paleoclimatology, though they will not provide the clear tree rings found in faster-growing trees at lower elevations.

There is plentiful residual snow on the ground, which is an important source of the plant's water supply, but also reinforces the high altitude, typically above 10,000 feet, at which Bristlecones thrive. Part of their ecological niche is to live on soils and in places where few other plants are able to make a living.

17.2.3 The dendrochronology principle of differential annual tree ring growth

This diagram illustrates the dendrochronology principle of differential annual tree ring growth. All else being equal, wider rings indicate periods of wetter climate and greater growth, while narrower rings indicate a drier and less productive year. Note that these rings may be sampled by a hollow core that does not kill the tree; not every dendrochronologic sample involves cutting down the tree. If the tree is cut down, then the slice of the trunk used to establish dendrochronology is referred to as a "cookie." These cookies and cores allow for examination of growth differentials and extraction of material for isotopic analysis.

The main image in the diagram is a cross-section of a tree trunk, with specific features identified. At the very center of the trunk is a small circle labeled "first-year growth." Moving outward, a wide tree ring indicates a rainy season, which a narrow tree ring indicates a dry season. Between two rings we see a thick black area that is labeled "scar from a forest fire." A close-up of one area shows the light and darker bands of the tree rings. Thicker light areas indicate spring/early summer growth, while the thinner and darker bands indicate late summer/fall growth.

17.2.4 California Palmer Drought Severity Index Scale

The Palmer Drought Index Scale from the year 1000 to the year 2000. Lower numbers (-8, -6, -4, etc.) indicate drier climate conditions, while higher numbers (2, 4, 6, etc.) indicate wetter years. This thousand-year record shows showing dry periods/wet periods in California from the years 1000 to 2000, as shown from a baseline of 0, with variation upwards indicating wetter periods, and variations downward drier periods.

The period of 1900-2000 show some wet spikes and dry spikes; the fear of climate change-induced drought is that future iterations of this graph will show primarily dry numbers. Of particular note are the low (dry) pulses that occur after the year 1100 and again, in several pulses, throughout the 1200s, 1300s, 1400s, 1500s, 1600s, 1700s, 1800s, and 2000s.

17.3.1 San Francisco's annual precipitation profile

Monthly precipitation profile for San Francisco using NOAA data from 1991 to 2020. The twelve steps on the bottom each correspond to a month (Jan to Dec), while the axis to the left shows precipitation in mm, from 0 to 130. January and December clock in between 110 and 120 mm, respectively, while July-August-September report zero to a few mm.

What this pattern shows is the "Mediterranean" climate noted by long, dry summers with virtually no precipitation from June-Sep, punctuated by wetter winters with rainfall concentrated Nov/Dec/Jan/Feb. Even these rainfall concentrations are something of a misnomer, because precipitation does not fall steadily, as it would in, say, Seattle, but rather comes from just 1-2 major storms that inundate and overwhelm city water systems.

Monthly precipitation for San Francisco (NOAA dataset, 1991 - 2020)

Month	Precipitation in mm
January	112
February	111
March	80
April	41
May	18
June	5
July	1
August	2
September	3
October	24
November	66
December	121

17.3.2 The rain shadow effect across California from Monterey to Death Valley

A elevation cross-section of California from Monterey to Death Valley, with a vertical exaggeration of 30x. Starting in the west near Monterey, we move past the coastal ranges into the flatness of the Central Valley, then begin a long climb up the west face of the Sierra Nevada. At this point the diagram shows rainclouds with drops of rain descending on the Sierran foothills, indicating the process of moisture being precipitated as it rises in elevation (orographic precipitation). The steep east side of the Sierra Nevada therefore creates a rain shadow in the Owens Valley. The White-Inyo mountains create another rain shadow for the Panamint Valley, and the Panamint Hills likewise form another rain shadow for Death Valley.

What this shows is that while precipitation flows from the west (left) to the east (right), when it encounters the Sierra Nevada, much of that moisture is removed by orographic precipitation, and indicated by the cloud and rain drops. Additional rain shadows remove even more moisture before whatever is left arrives in Death Valley, which is one of many factors why Death Valley is one of the driest spots on the planet.

The profile is exaggerated in order to display the height differences in a way greater than would actually be encountered if one were, for example, seeing this profile in a plane traversing the same course.

17.3.3 The Köppen climate classifications for California

California with different regions parsed into various Köppen climate classifications. The Köppen climate classifications are a way of parsing climate zones such as "Dsc (Dry-summer subarctic)" and "BSh (hot semi-arid)." Note that only four of the categories indicate "Mediterranean" conditions, though "Mediterranean" is the most common way to describe California's climate. Problems with this oversimplification are detailed in the chapter section.

This diagram divides California into 11 such categories

• Desert climates dominate the southeastern part of the state:
  • BWh (hot desert), shown in bright red, covers much of southeastern California, including areas near the Mojave and Colorado Deserts.
  • BWk (cold desert) appears in lighter pink in some inland and higher-elevation desert regions.
• Semi-arid climates appear in transition zones:
  • BSh (hot semi-arid) and BSk (cold semi-arid), shown in orange and light tan, occur around desert margins and interior valleys.
• Mediterranean climates cover much of the populated coastal and inland regions:
  • Csa (hot-summer Mediterranean), shown in bright yellow, dominates the Central Valley and large portions of Southern California.
  • Csb (warm-summer Mediterranean), in olive green, is common along the northern and central coast and foothill regions.
  • Csc (cold-summer Mediterranean) appears in limited high-elevation coastal or mountainous areas.
• Mountain and cooler climates are concentrated in higher elevations:
  • Cfb (oceanic) occurs in small coastal and northern areas.
  • Dsb (warm-summer continental Mediterranean) and Dsc (dry-summer subarctic) appear mainly along the Sierra Nevada range, shown in purple tones.
  • ET (tundra), shown in gray, is limited to the highest mountain peaks.

The diagram discusses its sources as "Data sources: 1991-2020 climate normals from PRISM Climate Group, Oregon State University; outline map from US Census Bureau."

17.3.4 Extremes in maximum temperature, 1910-2022

Extremes in maximum temperature from 1910 to 2022, with percentages above or below a baseline. Above-average temperatures begin to become much more common after 1980, and after 2010 are all classified as "much above normal." This reflects the warming trends worldwide during these time periods.

The title is "West extremes in maximum temperature (Step 1) annual (January - December)." Lines indicate "much above normal," "much below normal," and a "9-point binomial filter."

Particular note should be given to the low extremes associated with the 1982-1983 and 1997-1998 El Nino events. Also of note is the trend that after the year 2000, virtually every temperature reading is listed as "much above normal."

The trend from 1910-1980 begins with a small range; however, this range grows greatly in the 1982-1983 period and then expands dramatically after 2010.

17.3.5 Snow Water Equivalent at Donner Summit, CA

Snow Water Equivalent (SWE) at Donner Summit from the years from 1910 to 2020. SWE is in inches, ranging from 0 to 90. What there is significant variation, both high and low, across the time period, the lowest measurements occur within the last few decades, including a reading in 2015 near zero. The table below extracts an estimate for each decade

Estimated April 1 SWE by Decade

Decade	Estimated Avg SWE (inches)
1910–1919	45
1920–1929	30
1930–1939	44
1940–1949	39
1950–1959	40
1960–1969	38
1970–1979	41
1980–1989	36
1990–1999	42
2000–2009	34
2010–2019	20

  

17.3.6 Illustration of an atmospheric river

A January 2023 atmospheric river forming in the Pacific and heading directly toward California, with a narrow counter-clockwise rotation of moisture moving from the west to the east, hitting California and spreading out along the California coastline. This is typical of the way we receive the majority of our rainfall.

17.3.8 An illustration of the Reber Plan

The quixotic Reber Plan, which was never enacted, but which would have catastrophically altered California water by building a dam across San Francisco Bay, capturing the largest freshwater drainage in the state. The main barrier in the Reber Plan would have been a dam from Pt. San Quentin to Richmond, west to east, roughly following the course of the Richmond-San Rafael bridge. Other inlets and bays would have been paved over. To the north, a shipping channel and lock system would have been constructed right through the current city of Richmond, allowing shipping to each the upper Sacramento river.

This plan was never fulfilled, but one can imagine the environmental devastation this would have wrought had it been constructed.

17.4.1 In a harbinger of future sea level rise, a King Tide splashes onto the streets

King Tide conditions at the San Francisco Embarcadero, where sea level is even with sidewalks and small waves splash salt water onto San Francisco streets. These King Tides give us an indication of what future sea level rise will look like, when the ocean level is this high at the normal high tide.

17.4.2 A graph showing the IPCC AR6 global sea level change projection

Projected sea level rises, with a range of uncertainty indicated on either side of the middle line. One axis tracks from the years 2020 to 2140, while another shows sea level change in meters from 0.2 to 1.6. The middle scenario shows over a meter of sea level rise by 2140. The trend line begins at 0.05 for 2020 with an uncertainty range of 0.03-0.07 meters. The trend lines moves steadily upward steadily ending at roughly 1.2 in 2150 with an uncertainy range of 0.9 - 1.65 meters.

17.4.3 Observed and Projected Temperature Change in California

Historical, current, and project temperature changes in California. One axis shows years from 1900 to 2100, while another shows temperature changes in ^oF from -2 to 12. Projected changes are split between "high emissions" and "low emissions" scenarios. The lower emissions track puts us somewhere between 2 to 7^oF by 2100. However, we are firmly on the higher emission pathway right now, and if we follow that to its worst conclusions, then we could be looking at increases in overall temperatures on the order of 12^oF by 2100.

Estimated Temperature Change by Time Range

Time Range	Observation	Modeled Historical	Lower Emmissions	Higher Emissions
1900–1920	−1.5 to +0.5	−2.0 to +1.5	N/A	N/A
1920–1940	−1.0 to +2.5	−1.8 to +1.8	N/A	N/A
1940–1960	−1.5 to +1.5	−2.0 to +1.7	N/A	N/A
1960–1980	−1.0 to +2.0	−1.5 to +2.2	N/A	N/A
1980–2000	0.0 to +2.5	−1.0 to +3.0	N/A	N/A
2000–2020	+0.5 to +4.0	−0.5 to +3.5	−0.5 to +1.5	−0.5 to +2.0
2020–2040	N/A	N/A	+0.5 to +2.5	+1.0 to +4.0
2040–2060	N/A	N/A	+1.5 to +4.0	+3.0 to +6.5
2060–2080	N/A	N/A	+2.0 to +5.0	+5.0 to +10.0
2080–2100	N/A	N/A	+2.0 to +5.5	+6.0 to +13.0

17.5.1 A dark vision of a future affected by climate change disasters

An AI imagining of the future Los Angeles skyline under severe climate change. Note the flooded roads lined with palm trees, on which cars gingerly make their way through standing water, while the sky is reminiscent of the actual sky conditions on 9 September 2020, which involved an orange-red sky created by an inversion of particles created by out-of-control wildfires. It is interesting to contemplate that all of our infrastructure--skyscrapers, bridges, roads--will remain abandoned for a while, even if future climate change makes conditions on Earth unlivable for humans.