17.4: The Future

The Future

Tides rarely attract a crowd.

But in California, under just the right positions and orbits of the moon and the sun, unusually high tides appear, offering an ominous glimpse of what rising sea levels will look like in the future. These “King Tides” are of interest to earth scientists and the California Coastal Commission, which runs the California King Tides Project, tasked with distributing information about upcoming King Tides and collecting citizen photographs as a way to visualize future sea levels. Their motto: “Snap the shore, see the future.”

And the problematic future looks like Figure \(\PageIndex{1}\):

Figure \(\PageIndex{1}\): In a harbinger of future sea level rise, a King Tide splashes onto the streets of the Embarcadero at the San Francisco waterfront. "King tide" by Steven Newton, is licensed under CC BY-NC 4.0. Access a detailed description.

In this picture, a King Tide puts the ocean nearly level with the Embarcadero, the major traffic artery forming San Francisco’s eastern waterfront. In our current time, King Tides in San Francisco spill only the larger waves onto the streets. Some day, normal high tides will periodically flood the entire road, forcing intermittent traffic closures. As sea level continues to rise, this flooding will happen even under low tide conditions, necessitating the closure of the Embarcadero and the abandonment of San Francisco’s coastline to the swelling brine.

The climate future of California can be assessed in a number ways. We will examine sea level rise and increased heat. These are far from the only effects California can expect from climate change, but understanding them is a place to start.

Sea level rise

By 2050, we can expect sea level to rise 0.3 meters. While this might not seem so much, 0.3 meters is more than the entire last century. And the oceans are just getting started with us.

A couple of factors affect sea level. Thermal expansion is one factor rooted in basic physics: objects expand when heated, and contract when cooled. Water is no exception. The vast majority of climate change heat is being absorbed by the world’s oceans, with the consequence that sea level rise will happen from thermal expansion alone.

There is the additional factor of the melting of land-based ice. As glaciers on land liquefy, their water transfers from land into the oceans–imagine ice-water fire hoses in Greenland and Antarctica aimed directly into the seas. (The distinction of land-based ice from floating sea ice is important, because floating sea ice, which forms seasonally in the Arctic and Antarctica, has no net effect on sea level because it already displaces its volume.)

The best source for information on climate topics comes from the Intergovernmental Panel on Climate Change (IPCC), which periodically releases assessment reports, the most current of which is called AR6 (assessment report number six; released between 2021 and 2023). According to the IPCC AR6, we can attribute 38% of sea level rise to thermal expansion, and 41% from glacial melt (Fox-Kemper et al., 2021). Both of these factors contribute to worldwide sea level rise, but California experiences additional phenomena. The El Niño Southern Oscillation (ENSO) affects ocean temperature on short time scales, and the Pacific Decadal Oscillation (PDO) on longer time scales, each altering the temperature of oceanic waters off California’s coast.

How bad will California sea level rise become? There are many different estimates, each based on assumptions about the future we cannot fully know right now.

The IPCC AR6 details a range of projections for sea level rise; the projections differ based on the degree to which future governments do or do not control greenhouse emissions. Figure \(\PageIndex{2}\) shows a middle ground for these scenarios:

Figure \(\PageIndex{2}\): A graph showing the IPCC AR6 global sea level change projection under the most likely scenario (SSP3-7.0), with the peach color indicating a range of uncertainty. "IPCC projection" by NASA, licensed under public domain. Access a detailed description.

While this projection goes out to the year 2140, visible sea level changes are expected much sooner. According to NOAA, “Sea level along the U.S. coastline is projected to rise, on average, 10-12 inches (0.25 - 0.30 meters) in the next 30 years (2020-2050).”

Even a small amount of sea level rise will have disastrous effects. Higher salt water levels will increase the risk of saline encroachment into freshwater reservoirs. Higher seas will magnify erosional issues along coasts. And because so much of our infrastructure is built so close to the existing sea level, a minor rise can have major effects.

A report by the California Legislative Analyst's Office determined that by 2050, sea level rise will cost California between $8-10 billion of existing property. Slightly more than a meter of sea level rise will displace 28,000 residents of the San Francisco Bay Area. And in the 2 meter range of sea level rise, about two-thirds of Southern California beaches will disappear by 2100.

Increased heat

The extent of California’s future heating depends on a number of variables. IPCC projections typically employ a wide range of projections–high carbon emissions, medium carbon emissions, low carbon emissions–to sweep in the possibilities. However, the worldwide inability of governments to effect meaningful carbon reductions puts us squarely in the “high emissions” zone; when actual observations are compared to projections, the observations almost always meet or exceed the modeled projections for the highest emissions scenarios.

Figure \(\PageIndex{3}\), a chart of projections for California, is produced by NOAA:

Figure \(\PageIndex{3}\): Observed and Projected Temperature Change in California. "Temperature change" by NOAA is in the public domain. Access a detailed description.

The world is not in the lower emissions scenario, but if we were, then the mildest amount of temperature increases in California would range between 2-8^oF; these are temperatures added to the normal average.

Our carbon emissions more closely follow the higher emissions scenario. What this means is that by the year 2100, at the extreme end we can project California temperatures to soar above 12^oF from the norm. While this heat will be unevenly distributed, it is not hard to imagine the July daily mean temperature for Los Angeles rising from its present 73^oF to 85^oF. And for areas of higher elevation, where the vital annual snow pack forms, it is not hard to imagine temperatures rising to the point where very little snow forms and winter precipitation happens primarily as ephemeral rains.

Query \(\PageIndex{1}\)

Query \(\PageIndex{1}\)

References

1. U.S. Energy Information Administration (March 2023). Highlights for air conditioning in U.S. Homes by state, 2020. Retrieved December 6, 2023, from https://www.eia.gov/consumption/residential/data/2020/state/pdf/State%20Air%20Conditioning.pdf
2. Bump, P. (2022, September 7). Californians may no longer be able to avoid air conditioning. The Washington Post. https://www.washingtonpost.com/politics/2022/09/07/californians-may-no-longer-be-able-avoid-air-conditioning/
3. Williams, A.P., Cook, B.I., and Smerdon, J.E. (2022). Rapid intensification of the emerging southwestern North American megadrought in 2020-2021. Nature Climate Change, 12(3), 232-234. https://doi.org/10.1038/s41558-022-01290-z
4. National Public Radio (2023, January 9). California is getting drenched. So why can't it save water for the drought? NPR.org. Retrieved November 9, 2023, from https://www.npr.org/2023/01/07/1147494521/california-weather-storm-water
5. Shao, E., Rojanasakul , M., & Popovich, N. (2023, March 17). A Very Wet Winter Has Eased California’s Drought, but Water Woes Remain. The New York Times. https://www.nytimes.com/interactive/2023/climate/california-drought.html
6. Cassidy, E. (January 2023). Atmospheric River Lashes California. NASA Earth Observatory. Retrieved December 8, 2023, from https://earthobservatory.nasa.gov/images/150804/atmospheric-river-lashes-california
7. Vartabedian, R. (2023, January 13). In a Drought, California Is Watching Water Wash Out to Sea. The New York Times. https://www.nytimes.com/2023/01/13/us/california-drought-storms-water-storage.html