Answering the question of “how high will seas rise” is tricky. Perhaps the best response is “it depends.” There are many factors that interact in complex ways that will help determine future sea level rise. But fortunately, there are scientists much smarter than I who have done the legwork and presented their findings through scientific journals and major reports in the past few years. Let’s go through some of the major findings that are relevant to finding how much sea level rise we should expect in the coastal Southeast.
Projections As Ranges Due to Variables
Sea level rise projections are almost exclusively expressed as ranges, rather than a single number. Since there are variables that are either unknown at the present time or difficult to model, it would almost certainly be inaccurate to give a single, firm number as a prediction of sea level rise by a given date. Estimates are therefore given as a range of numbers to express the uncertainty.
Three of the primary variables that affect the accuracy of sea level rise projections are:
- how much carbon pollution is released in the future
- how much the seas rise as a result of higher temperatures
- the effect of feedback loops that may or may not be foreseen at the present
What Are the Projected Ranges of Sea Level Rise?
To help get an idea of how much sea level rise we in the coastal Southeast should expect, let’s walk through a few of the most significant recent estimates and then discuss how to consider these projections for local use.
It’s important to note here that when interpreting measures of sea level rise, one vertical foot doesn’t equal one horizontal foot. Given the shallow slope of land in the Southeast, one vertical foot of sea level rise could cause flooding or erosion of approximately 100—200 feet inland in South Carolina and as much as 1,000 feet inland in Florida. It follows that a similar proportional relationship could be displayed from a rise of anywhere from a few inches to a few feet.
As part of the U.S. National Climate Assessment process, the National Oceanic and Atmospheric Administration (NOAA) released a report last December, with the best available data to inform U.S. climate policy. Their findings:
“Scientists have very high confidence (greater than 90 percent chance) that global mean sea level will rise at least eight inches (0.2 meter) and no more than 6.6 feet (2.0 meters) [above 1992 levels] by 2100.”
The projections are broken down by various scenarios: low, intermediate-low, intermediate-high and high. As for what assumptions inform each scenario, NOAA says this:
- The lowest sea level change scenario (eight inch rise) is based on historic rates of observed sea level change. This scenario should be considered where there is a high tolerance for risk (e.g. projects with a short lifespan or flexibility to adapt within the near-term)
- The intermediate-low scenario (1.6 feet) is based on projected ocean warming
- The intermediate-high scenario (3.9 feet) is based on projected ocean warming and recent ice sheet loss
- The highest sea level change scenario (6.6 foot rise) reflects ocean warming and the maximum plausible contribution of ice sheet loss and glacial melting. This highest scenario should be considered in situations where there is little tolerance for risk.
This range of projected sea level rise (8 inch—6.6 feet by 2100) is similar to other studies that have been performed on the matter. The chart above shows a comparison of some of the more recent and significant projections of global sea level. They tend to be within the 8 inch—6.6 foot range. It’s important to note, however, that some of the difference between the projections is due to using different baseline years, different planning horizons (i.e. by 2050, 2060, 2100), and also varying modeling methodologies.
Of course if you are wondering which sea level rise projection to use to help you inform decisions regarding the future, it can be a tough process. Southeast Florida yields a precedent that is valuable for other coastal communities, struggling with this issue. As part of the work of the Southeast Florida Regional Climate Change Compact, the four participating counties drew up a “Unified Sea Level Rise Projection” to use for planning purposes. They ended up using the guidance numbers from the Army Corps of Engineers for their sea level rise planning.
The Intergovernmental Panel on Climate Change (IPCC), widely regarded as the most influential group of climate change experts in the world, just released an updated report on sea level rise projections as part of their fifth climate assessment report (AR5). It was interesting to see that the updated report upped the projections for future sea level rise in the wake of their last report receiving much criticism for low-balling sea level rise estimates. The new report is still considered by many scientists and observers to be biased on the low side due to the way it is modeled and the reported conservative nature of the organization’s projections.
Global vs. Local Sea Level Rise and Implications for the Southeast
While much of the scientific literature on sea level rise has focused on the global rate of sea level rise, it is critical to know that sea level does not change uniformly across the globe. Local sea level rise is affected by complex oceanographic factors such as ocean currents and gravitational pulls, as well as the fact that in some places, coastal land is sinking, yet in other places, the land is rising. Therefore, to understand the local impacts of sea level rise, it is important to consider local data alongside global averages of sea level rise.
The phenomenon of local relative sea level rise (RSLR) is perhaps best illuminated by the example of the Gulf coast, where the rate of land subsidence, or how fast the land is sinking, has been measured at about 10 millimeters per year over the last 60 years. Compare that to Key West, which has averaged about 2.24 mm rise per year (and has demonstrated very little land subsidence), or Charleston, which has averaged about 3.15 mm rise per year. At this rate, some Gulf coast areas need to plan for an absolute minimum of three feet of sea level rise by 2100, and realistically should be planning for more than six feet.
Another notable example of local sea level rise is the mid-Atlantic coast. Last year, a U.S. Geological Survey (USGS) study was published, saying that the mid-Atlantic coast, from North Carolina to Massachusetts has one of the fastest rates of sea level rise in the world, independent of vertical land movement (rising or sinking). The USGS study found that oceans are rising on the mid-Atlantic coast at three to four times the global rate of sea level rise. This phenomenon is thought to be caused at least in part to the slowdown of the Gulf Stream’s current and thus a “backing up” of water.
Putting these two examples of local sea level rise together paints a very concerning picture for the future of the coastal Southeast. On top of the global mean sea level rise estimated in the previously mentioned reports, some parts of the Southeast will also have to plan for a significant amount of extra rise from unique oceanographic factors or extra relative rise from extreme land subsidence.
How to Plan for Sea Level Rise Given Uncertainties
Given that local sea level rise may differ significantly from global averages that are projected for the future, the Southeast region needs a greater understanding of where the localized effects on sea level rise are and what is causing them. Local universities can prove invaluable for studying these local effects and they should be supported accordingly.
Furthermore, when trying to determine rates of sea level rise for local planning purposes, it might be worthwhile to plan for higher rates of rise for planning protection for high-value assets (i.e. the “better safe than sorry” approach) and reserve the use of lower rates of rise for assets of lower value or that are less critical to stay dry.
As was mentioned toward the beginning of this post, while some of the uncertainty of how much sea levels will rise in the future is due to limits of modeling, a large portion of the uncertainty is based on how much we continue to pollute. Cutting our carbon pollution soon won’t stop sea level rise from happening in the near term, but it will slow it over the long term. For this reason, I consider it critical that this variable be given careful consideration by anyone trying to plan for sea level rise. The good news is that to some degree, we are in the drivers seat and we have some amount of deciding power whether or not we will choose a course that takes us to the high end of the projections or the low end.
Visit EcoWatch’s CLIMATE CHANGE page for more related news on this topic.
By Katy Neusteter
The Biden-Harris transition team identified COVID-19, economic recovery, racial equity and climate change as its top priorities. Rivers are the through-line linking all of them. The fact is, healthy rivers can no longer be separated into the "nice-to-have" column of environmental progress. Rivers and streams provide more than 60 percent of our drinking water — and a clear path toward public health, a strong economy, a more just society and greater resilience to the impacts of the climate crisis.
Public Health<img lazy-loadable="true" data-runner-src="https://assets.rebelmouse.io/eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJpbWFnZSI6Imh0dHBzOi8vYXNzZXRzLnJibC5tcy8yNTUyNDY3MC9vcmlnaW4uanBnIiwiZXhwaXJlc19hdCI6MTY2MDkxMTkwNn0.pyP14Bg1WvcUvF_xUGgYVu8PS7Lu49Huzc3PXGvATi4/img.jpg?width=980" id="8e577" class="rm-shortcode" data-rm-shortcode-id="1efb3445f5c445e47d5937a72343c012" data-rm-shortcode-name="rebelmouse-image" data-width="3000" data-height="2302" />
Wild and Scenic Merced River, California. Bob Wick / BLM<p>Let's begin with COVID-19. More than <a href="https://www.nytimes.com/interactive/2020/us/coronavirus-us-cases.html?name=styln-coronavirus&region=TOP_BANNER&block=storyline_menu_recirc&action=click&pgtype=LegacyCollection&impression_id=2f508610-2a87-11eb-8622-4f6c038cbd1d&variant=1_Show" target="_blank">16 million Americans</a> have contracted the coronavirus and, tragically,<a href="https://www.nytimes.com/interactive/2020/us/coronavirus-us-cases.html?name=styln-coronavirus&region=TOP_BANNER&block=storyline_menu_recirc&action=click&pgtype=LegacyCollection&impression_id=2f508610-2a87-11eb-8622-4f6c038cbd1d&variant=1_Show" target="_blank"> more than</a> <a href="https://www.nytimes.com/interactive/2020/us/coronavirus-us-cases.html?name=styln-coronavirus&region=TOP_BANNER&block=storyline_menu_recirc&action=click&pgtype=LegacyCollection&impression_id=2f508610-2a87-11eb-8622-4f6c038cbd1d&variant=1_Show" target="_blank">300,000 have died</a> due to the pandemic. While health officials encourage hand-washing to contain the pandemic, at least <a href="https://closethewatergap.org/" target="_blank">2 million Americans</a> are currently living without running water, indoor plumbing or wastewater treatment. Meanwhile, <a href="https://www.theguardian.com/us-news/2020/jun/23/millions-of-americans-cant-afford-water-bills-rise" target="_blank">aging water infrastructure is growing increasingly costly for utilities to maintain</a>. That cost is passed along to consumers. The upshot? <a href="https://research.msu.edu/affordable-water-in-us-reaching-a-crisis/" target="_blank">More than 13 million</a> U.S. households regularly face unaffordable water bills — and, thus, the threat of water shutoffs. Without basic access to clean water, families and entire communities are at a higher risk of <a href="https://www.americanprogress.org/issues/green/news/2020/08/05/488705/bridging-water-access-gap-covid-19-relief/" target="_blank">contracting</a> and spreading COVID-19.</p><p>We have a moral duty to ensure that everyone has access to clean water to help prevent the spread of the coronavirus. Last spring, <a href="https://nymag.com/intelligencer/2020/03/coronavirus-stimulus-bill-explained-bailouts-unemployment-benefits.html" target="_blank">Congress appropriated more than $4 trillion</a> to jumpstart the economy and bring millions of unemployed Americans back to work. Additional federal assistance — desperately needed — will present a historic opportunity to improve our crumbling infrastructure, which has been <a href="https://www.theguardian.com/us-news/2020/jun/23/millions-of-americans-cant-afford-water-bills-rise" target="_blank" rel="noopener noreferrer">grossly underfunded for decades</a>.</p><p>A report by my organization, American Rivers, suggests that <a href="https://s3.amazonaws.com/american-rivers-website/wp-content/uploads/2020/07/09223525/ECONOMIC-ENGINES-Report-2020.pdf" target="_blank" rel="noopener noreferrer">Congress must invest at least $50 billion</a> "to address the urgent water infrastructure needs associated with COVID-19," including the rising cost of water. This initial boost would allow for the replacement and maintenance of sewers, stormwater infrastructure and water supply facilities.</p>
Economic Recovery<p>Investing in water infrastructure and healthy rivers also creates jobs. Consider, for example, that <a href="https://tinyurl.com/y9p6sgnk" target="_blank">every $1 million spent on water infrastructure in the United States generates more than 15 jobs</a> throughout the economy, according to a report by the Value of Water Campaign. Similarly, <a href="https://tinyurl.com/yyvd2ksp" target="_blank">every "$1 million invested in forest and watershed restoration contracting will generate between 15.7 and 23.8 jobs,</a> depending on the work type," states a working paper released by the Ecosystem Workforce Program, University of Oregon. Healthy rivers also spur tourism and recreation, which many communities rely on for their livelihoods. According to the findings by the Outdoor Industry Association, which have been shared in our report, "Americans participating in watersports and fishing spend over <a href="https://s3.amazonaws.com/american-rivers-website/wp-content/uploads/2020/06/30222425/Exec-summary-ECONOMIC-ENGINES-Report-June-30-2020.pdf" target="_blank">$174 billion</a> on gear and trip related expenses. And, the outdoor watersports and fishing economy supports over <a href="https://s3.amazonaws.com/american-rivers-website/wp-content/uploads/2020/06/30222425/Exec-summary-ECONOMIC-ENGINES-Report-June-30-2020.pdf" target="_blank">1.5 million jobs nationwide</a>."</p><p>After the 2008 financial crisis, Congress invested in infrastructure to put Americans back to work. The American Recovery and Reinvestment Act <a href="https://thehill.com/blogs/congress-blog/economy-a-budget/25941-clean-water-green-infrastructure-get-major-boost" target="_blank">of 2009 (ARRA) allocated $6 billion</a> for clean water and drinking water infrastructure to decrease unemployment and boost the economy. More specifically, <a href="https://www.conservationnw.org/news-updates/us-reps-push-for-millions-of-restoration-and-resilience-jobs/" target="_blank" rel="noopener noreferrer">an analysis of ARRA</a> "showed conservation investments generated 15 to 33 jobs per million dollars," and more than doubled the rate of return, according to a letter written in May 2020 by 79 members of Congress, seeking greater funding for restoration and resilience jobs.</p><p>Today, when considering how to create work for the <a href="https://www.bls.gov/news.release/pdf/empsit.pdf" target="_blank" rel="noopener noreferrer">10.7 million</a> people who are currently unemployed, Congress should review previous stimulus investments and build on their successes by embracing major investments in water infrastructure and watershed restoration.</p>
Racial Justice<p>American Rivers also recommends that Congress dedicate <a href="https://s3.amazonaws.com/american-rivers-website/wp-content/uploads/2020/07/09223525/ECONOMIC-ENGINES-Report-2020.pdf" target="_blank" rel="noopener noreferrer">$500 billion for rivers and clean water over the next 10 years</a> — not just for the benefit of our environment and economy, but also to begin to address the United States' history of deeply entrenched racial injustice.</p><p>The <a href="https://www.epa.gov/npdes/sanitary-sewer-overflows-ssos" target="_blank" rel="noopener noreferrer">23,000-75,000 sewer overflows</a> that occur each year release up to <a href="https://www.americanrivers.org/2020/05/fighting-for-rivers-means-fighting-for-justice/#:~:text=There%20are%20also%2023%2C000%20to%2075%2C000%20sanitary%20sewer,to%20do%20with%20the%20mission%20of%20American%20Rivers." target="_blank" rel="noopener noreferrer">10 billion gallons of toxic sewage</a> <em>every day</em> into rivers and streams. This disproportionately impacts communities of color, because, for generations, Black, Indigenous, Latinx and other people of color have been <a href="https://www.scientificamerican.com/article/flooding-disproportionately-harms-black-neighborhoods/" target="_blank" rel="noopener noreferrer">relegated</a> to live in flood-prone areas and in neighborhoods that have been intentionally burdened with a lack of development that degrades people's health and quality of life. In some communities of color, incessant flooding due to stormwater surges or <a href="https://www.ajc.com/opinion/opinion-partnering-to-better-manage-our-water/7WQ6SEAQP5E4LGQCEYY5DO334Y/" target="_blank" rel="noopener noreferrer">combined sewer overflows</a> has gone unmitigated for decades.</p><p>We have historically treated people as separate from rivers and water. We can't do that anymore. Every voice — particularly those of people most directly impacted — must have a loudspeaker and be included in decision-making at the highest levels.</p><p>Accordingly, the new administration must diligently invest in projects at the community level that will improve lives in our country's most marginalized communities. We also must go further to ensure that local leaders have a seat at the decision-making table. To this end, the Biden-Harris administration should restore <a href="https://www.epa.gov/cwa-401#:~:text=Section%20401%20Certification%20The%20Clean%20Water%20Act%20%28CWA%29,the%20United%20States.%20Learn%20more%20about%20401%20certification." target="_blank">Section 401 of the Clean Water Act</a>, which was undermined by the <a href="https://earthjustice.org/news/press/2020/tribes-and-environmental-groups-sue-trump-administration-to-preserve-clean-water-protections#:~:text=Under%20Section%20401%20of%20the%20Clean%20Water%20Act%2C,seeks%20to%20undermine%20that%20authority%20in%20several%20ways%3A" target="_blank">Trump administration's 2020 regulatory changes</a>. This provision gives states and tribes the authority to decide whether major development projects, such as hydropower and oil and gas projects, move forward.</p>
Climate Resilience<p>Of course, the menacing shadow looming over it all? Climate change. <a href="https://media.ifrc.org/ifrc/wp-content/uploads/2020/11/IFRC_wdr2020/IFRC_WDR_ExecutiveSummary_EN_Web.pdf" target="_blank">More than 100 climate-related catastrophes</a> have pummeled the Earth since the pandemic was declared last spring, including the blitzkrieg of megafires, superstorms and heat waves witnessed during the summer of 2020, directly impacting the lives of more than <a href="https://media.ifrc.org/ifrc/wp-content/uploads/2020/11/IFRC_wdr2020/IFRC_WDR_ExecutiveSummary_EN_Web.pdf" target="_blank">50 million people globally</a>.</p><p>Water and climate scientist Brad Udall often says, "<a href="https://www.youtube.com/watch?v=xQhpj5G0dME" target="_blank">Climate change is water change</a>." In other words, the most obvious and dire impacts of climate change are evidenced in profound changes to our rivers and water resources. You've likely seen it where you live: Floods are more damaging and frequent. Droughts are deeper and longer. Uncertainty is destabilizing industry and lives.</p><p>By galvanizing action for healthy rivers and managing our water resources more effectively, we can insure future generations against the consequences of climate change. First, we must safeguard rivers that are still healthy and free-flowing. Second, we must protect land and property against the ravages of flooding. And finally, we must promote policies and practical solutions that take the science of climate disruption into account when planning for increased flooding, water shortage and habitat disruption.</p><p>Imagine all that rivers do for us. Most of our towns and cities have a river running through them or flowing nearby. Rivers provide clean drinking water, irrigate crops that provide our food, power our homes and businesses, provide wildlife habitat, and are the lifeblood of the places where we enjoy and explore nature, and where we play and nourish our spirits. Healthy watersheds help <a href="https://news.un.org/en/story/2020/03/1059952" target="_blank" rel="noopener noreferrer">mitigate</a> climate change, absorbing and reducing the amount of carbon in the atmosphere. Healthy rivers and floodplains help communities adapt and build resilience in the face of climate change by improving flood protection and providing water supply and quality benefits. Rivers are the cornerstones of healthy, strong communities.</p><p>The more than <a href="https://archive.epa.gov/water/archive/web/html/index-17.html" target="_blank" rel="noopener noreferrer">3 million miles</a> of rivers and streams running across our country are a source of great strength and opportunity. When we invest in healthy rivers and clean water, we can improve our lives. When we invest in rivers, we create jobs and strengthen our economy. When we invest in rivers, we invest in our shared future.</p>
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