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- 2022 Technical Report:          Overview
- 2022 Technical Report, Data, FAQs

# **2022 Sea Level Rise Technical Report**

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        -  **                    Download Full Report 

## **Download Report by Section**

        - ****Cover, Table of Contents, List of Figures, List of Tables** 
        - ****Executive Summary** 
        - ****Section 1: Introduction**
        - ****Section 2: Future Mean Sea Level: Scenarios and Observation-Based Assessments**  **Section 2 includes:**            - 2.1. Overview of Regional and Global Sea Level Rise
          - 2.2. Updates from Sweet et al. (2017)
          - 2.3. Near-Term Sea Level Change (2020-2050)
          - 2.4. Long-Term Sea-Level Change (2050-2150)
          - 2.5. Scenario Divergence and Tracking 
        - ****Section 3: Extreme Water Levels and Changing Coastal Flood Exposure**  **Section 3 includes:**            - 3.1. Regional Frequency Analysis of Tide Gauge Data
          - 3.2. Average Event Frequencies of Extreme Water Levels
          - 3.3. Methods to localize the Gridded extreme water Level (EWL) Event Probabilities
          - 3.4. The Changing Nature of Coastal Flood Risk 
        - ****Section 4: Use Cases**  **Section 4 includes:**            - 4.1. Mapping of NOAA Flood Thresholds and Flood Frequencies
          - 4.2. Application of Scenarios, Observation-Based Extrapolations, and Extreme Water Levels              
          - 4.3. Growing Risk to Combined Storm and Wastewater Systems from Sea Level Rise
          - 4.4. Using InSAR technology for determining regional vertical land motion rates and                suitability for using to compute long-term sea level rise projections. 
        - ****Section 5: Conclusions**
        - ****Section 6: Acknowledgements**
        - ****Section 7: References**
        - ****Appendices**  **Appendices include:**            - A1: Tables and Figures
          - A2: Methods Appendix: Extreme Water Levels and Alaska Coastal Flood Height 
        - ****Section 8: Acronyms**
        - ****Report Data and Associated Tools**

When it comes to incorporating sea level rise projections into community planning initiatives, the path is not crystal clear, as there are many factors to consider. Our companion Application Guide for the 2022 Sea Level Rise Technical Report helps the reader wade through the considerations and arrive at what’s best for their community.          

**Return to Technical Report                  Overview**

**Explore Report Data and                  Tools**

##### **Frequently Asked Questions:**

**Introduction**

**Impacts and Causes of Sea Level                  Rise**

**Sea Level Rise                  Scenarios**

**2022 Federal Sea Level Rise                  Scenarios**

**2022 Federal Observation-Based                  Extrapolations and Extreme Water Levels**

**Accessing Data and Applying Sea Level                  Rise Information to Decision Making**

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**                Download the Companion Application Guide for the 2022 Sea Level Rise Technical Report [ENGLISH]
  
**                    Download the Companion Application Guide for the 2022 Sea Level Rise Technical Report [SPANISH]
  When it comes to incorporating sea level rise projections into community planning initiatives, the path for each community, for each project, is not crystal clear, as there are many factors to consider.  That’s what this application guide helps the reader do — wade through the considerations and arrive at what’s best for their community. This publication is a companion for the 2022 Sea Level Rise Technical Report, which represents the most up-to-date sea level rise information available. The application guide includes four sections:               - A description of the content within the technical report.
- An in-depth discussion of items to be considered when planning for sea level rise.
- Approaches for integrating the 2022 sea level rise scenarios into community planning initiatives.
- Additional resources to be used as communities explore next steps.
**Frequently Asked Questions**
          This technical report provides a synthesis of the most recent science          related to sea level rise, and serves as a key technical input for the          Fifth National Climate Assessment that is underway. The report does not          provide guidance or design specifications for a specific project, but is          intended to help inform federal agencies, tribes, state and local          governments, and stakeholders in coastal communities about current and          future sea level rise. The executive summary provides key messages, and the          body of the report provides detailed, technical information about the data,          modeling, and analysis behind the report’s findings. As with the previous          2017 technical report, global mean sea level rise scenarios are          regionalized for the U.S. coastline.        

          Data from the report are being incorporated into current and planned agency          tools and services, and are immediately available in NOAA’s                      Sea Level Rise Viewer          and NASA’s                      Task Force Projection Tool. Readers interested in accessing information for a particular community or          region can look to these tools.        

Frequently asked questions and answers are available below.
Impacts and Causes of Sea Level Rise1. What is impacted by                  sea level rise? ****
                  Tens of millions of people in the U.S. and hundreds of millions globally live in areas that are at                  risk of coastal flooding. Sea level rise does not act alone — rising sea levels, along with sinking                  lands, will combine with other coastal flood factors like storm surge, wave effects, river flows, and                  heavy rains to significantly increase the exposure of coastal communities, ecosystems, and economies.                  Sea level rise threatens infrastructure necessary for local jobs, regional industries, and public                  safety, such as roads, subways, drinking water supplies, power plants, oil and gas wells, and sewage                  treatment systems.                

                  Long-term sea level rise will affect the extent, frequency, and duration of coastal flooding events.                  High-tide flooding events that occur only a few times a year now may occur once a month, or once a                  week in the coming decades. These same water level changes may also increase coastal erosion and                  groundwater levels. Elevated groundwater levels can lead to increased rainfall runoff and compromised                  underground infrastructure, such as public utilities, septic systems, and structural foundations.                  Higher water levels also mean deadly and destructive storm surges, wave impacts, and rainwater are                  unable to drain away from homes and businesses. 

See Section 1.1 of the technical report for more                    information.
2. What causes sea level                  rise? ****
The two major causes of                  global mean sea                    level                  rise are the expansion of ocean water as it warms (thermal expansion) and                  the added water from land-based ice (e.g., mountain glaciers and ice                  sheets) as it melts. Both of these processes are driven by increased global                  temperatures that are associated with greenhouse gas emissions. At a local level, any vertical land motion that may be occurring — from either natural or anthropogenic factors — can cause changes in ‘relative sea level.’                 

See Section 1.1 of the technical report for more                    information.
3. What is the                  connection between emissions, temperature change, and                  sea level rise? ****
There is strong evidence in the geologic record that global carbon dioxide levels, temperature                  levels, and sea levels have changed together through time. Human activities, especially                  emissions                    of greenhouse gasses, are the dominant cause of                  increasing                    global temperatures                  since the industrial revolution. When concentrations of greenhouse gasses                  in the atmosphere go up, temperatures also go up. As Earth warms, the ocean warms                  too, absorbing more than 90% of the increased atmospheric heat. When                  water warms, it expands — a process known as thermal expansion. This thermal                  expansion means that the volume of ocean water increases, which causes sea                  levels to rise. Rising air and ocean temperatures also cause glaciers and                  ice sheets to melt, which in turn increases the amount of water in the                  ocean. Both                  thermal                    expansion and melting land-based ice                  cause sea level to rise. Because the ocean is so large it retains heat for                  a long time. This means that even if global emissions and temperatures are                  reduced, sea levels will continue to rise for the coming decades and                  centuries.                

See Section 1.1 of the technical report for more                    information.
4. Why isn’t the rate                  of sea level rise the same everywhere? ****
Global sea                    level rise                  is caused by expanding ocean water and melting of land-based ice (see                  Questions 2 and 3). Regionally, other factors are at play, which means that                  there are differences in the amount and speed of sea level rise that will                  be experienced in each region of the United States. Regional or                  relative sea                    level                  rise has three drivers: changes in the ocean’s characteristics (*stereodynamics*), changes in                  the land’s height (*vertical land motion*), and changes in land ice and Earth (                  *gravitational, rotational, and deformational changes*).                

                  The first driver,                  stereodynamic                  sea level change, refers to changes in the ocean’s movement (circulation                  and currents) and its climate (temperature and saltiness). Trade winds and                  currents can push water higher, or lower, in different regions. Freshwater                  added from melting ice sheets and glaciers can shift ocean circulation                  patterns in different regions by changing the saltiness, temperature, and                  density of the water.                

                  Another reason for differences in regional sea level is                  *vertical                      land motion*. Across the U.S., land is sinking or rising at different rates and times,                  and this affects how high sea level rises in a region. Vertical land motion                  can be a result of geologic processes (e.g. the movement of tectonic                  plates); human activity, such as removing groundwater or fossil fuels from                  underground, which can cause the land to sink; or naturally-occurring                  sediment compaction and settling over time (e.g., subsidence in the                  Mississippi River delta).                

                  Changes in land ice and solid Earth – also called *gravitational, rotational, and                    deformational* changes – can also                  affect regional sea level. When                  ice                    sheets                  and                  glaciers                  melt or lose mass, this adds freshwater to the oceans and changes the                  gravity, deformation, and rotation of the Earth, which then contributes to higher sea level rise at                  locations farther away from the ice melting source than locations close by. These patterns of sea                  level rise are known as “fingerprints” and are the reason that ice mass loss from distant Antarctica                  will impact the U.S. coastline more so than ice mass loss from Greenland.                

See Section 2.1 of the technical report                    for more information.
5. How much has sea                  level risen in the past 100 years? ****
Global mean sea level, or the average height of the ocean surface, has risen 6 - 8 inches (15 - 20 centimeters) since 1920. In the continental U.S., relative sea level has risen about 10 - 12 inches (25 - 30 centimeters) over the same period. Observational data from tide gauges and satellites also show that sea level rise, both globally and along the continental U.S., is accelerating, with more than a third of that rise having occurred in the past two and a half decades (see NOAA                  and NASA portals for                  altimeter-based global rates and NOAA                  for local tide gauge rates).                
Sea Level Rise Scenarios6. What are sea level                  rise scenarios and how are they developed? ****
Sea level rise scenarios represent possible future sea level changes in response to increasing                  greenhouse gas emissions and ocean and atmospheric warming. These scenarios allow people to consider                  future impacts and responses and ask “what if?” questions about the future to support planning and                  decision-making. Sea level rise scenarios are used to communicate how much sea level rise could occur,                  under what circumstances, and by when. They also show how sea level rise might occur globally and                  locally.                

Sea level rise scenarios are generally based upon climate model outputs. These climate models allow                  scientists to simulate different responses, such as how the ocean might continue to warm, where ice                  melts and major ice sheets dynamically respond, and where and how the additional water disperses                  around the world’s ocean and affects circulation patterns. These responses differ under models that                  use different bounding conditions associated with various amounts of greenhouse emissions and ocean                  and atmospheric warming projections. Thus sea level rise scenarios help us plan in the face of                  uncertainty by providing a range of possible futures that help represent a) potential future                  human-driven greenhouse gas emissions, and b) how earth’s physical processes will respond to increased                  temperatures.
7. What are shared                  socioeconomic pathways and representative concentration                  pathways, and are they part of this technical report?****
Shared                    socioeconomic pathways                  describe how society, economics, and demographics may change globally over the next century. Depending                  on which pathway our global community actually follows, the amount of warming — and hence the amount                  of sea level rise — could be very different. These shared socioeconomic pathways are used in the                  Intergovernmental Panel on Climate Change’s Sixth                    Assessment Report,                  released in 2021.                

Representative concentration pathways are another frame of reference for evaluating future climate                  changes and were used in the Intergovernmental Panel on Climate Change’s Fifth Assessment Report.                  Representative concentration pathways represent different amounts of net radiative forcing by the end                  of the 21st century — in other words, the extra heat trapped in the atmosphere due to future amounts                  of greenhouse gasses — but the pathway of emissions or social conditions to get there are not                  specified.                

In the 2017 sea level rise technical report, scenarios were related to representative concentration                  pathways. The 2022 report and data employ the underlying methods and output from the Sixth Assessment                  Report and their dependency on shared socioeconomic pathways, but focus more on how these scenarios                  relate directly to different amounts of end-of-century surface warming associated with the pathways                  (see Question 3).                

                  See Section 2.4 of the technical report                    for more information.]                
8. What does it mean                  to have “uncertainty” in sea-level rise scenarios? ****
                  There are two types of uncertainty that are important to consider when                  thinking about future sea level changes: 1) uncertainty in representing or                  modeling the physical processes that cause sea level change known as *process uncertainty*, and                  2) uncertainty in how human behavior will                  drive future emissions and ensuing warming known as *emissions uncertainty*. The suite of                  projections in this report captures both *process uncertainty* and *emissions                    uncertainty.*

*Process uncertainty*                  is associated with how well we currently understand why sea level has                  changed in the past and how it will change in the future at specific times                  and locations. To capture *process uncertainty* in sea level rise                  projections, there is a range of uncertainty around each individual                  scenario (i.e., the low/17th%, median/50% and high/83rd% values for each                  particular scenario). The farther forward in time we move, the greater the                  uncertainty around each projection.                

*Emissions uncertainty* is captured in the range between the five global mean sea level rise                  scenarios: Low (1 foot; 0.3 meters), Intermediate Low (1.6 feet; 0.5 meters), Intermediate (3.3 feet;                  1.0 meter), Intermediate High (4.9 feet; 1.5 meters), and High (6.6 feet; 2.0 meters). In other words,                  the range between the five sea level scenarios is closely connected to emissions uncertainty, while                  the range around a given scenario is associated with process uncertainty.                

In addition to process and emissions uncertainty, there is still scientific discussion and                  investigation underway on the potential for rapid ice sheet melt and collapse, sometimes referred to                  as low confidence processes. Currently there is no scientific consensus on whether rapid melt will occur                  and, if it does, what that process will look like. Given that it is possible, those processes are                  included in international and federal assessments. The possibility of rapid ice sheet melt is a                  significant driver in reaching the highest scenarios in the 2022 technical report.                

We know that throughout time, global sea levels have changed by tens to hundreds of meters over                  approximately 100,000-year cycles. And that in arriving at the stages of sea level equilibriums (the                  dips and humps of global sea levels through time), there is evidence of periods of rapid rise on the                  order of meters of rise over 100-year periods. Due to the “committed sea level rise” from continued                  warming of the ocean, over the course of the next several centuries the higher scenarios might be                  approached as “when, not if” if warming and emissions continue to rise unchecked. Or, put another way,                  there is uncertainty in how quickly the “dynamics” associated with ice sheets may affect future sea                  level rise, but not regarding whether or not global sea levels in the next several centuries will                  rise by at least a few meters.                

                  See Section 2.2.2 and Box 2.1 of the                    technical report for more information on uncertainty in sea-level rise.
Components of the Report and Changes to the Sea Level Rise Scenarios          Since 20179. What is included in                  the 2022 technical report? ****
The report has three main components: 
- Updated scenarios of global and regional sea levels out to the year                    2150.
- A focus on the near-term time period using observation-based                    trajectories out to 2050. 
- A new national gridded set of extreme water level probabilities that illustrate how the frequency                    of NOAA minor, moderate, and major high tide flooding events will change in frequency out to year                    2050 (See the questions on Observation-Based Extrapolations and Extreme Water Levels).
10. How are the sea level                  rise scenarios in this report different from                  the 2017 report? ****
The 2022 technical report includes five possible scenarios of global sea level rise by 2100: Low (1                  foot; 0.3 meters), Intermediate Low (1.6 feet; 0.5 meters), Intermediate (3.3 feet; 1.0 meter),                  Intermediate High (4.9 feet; 1.5 meters), and High (6.6 feet; 2.0 meters). These same scenarios were                  in the 2017 technical report, but the Extreme (8.2 feet; 2.5 meters) scenario included in 2017 has                  been removed (see Question 14).                

The 2100 projections for each global scenario stayed the same, since science suggests this range of                  futures remains possible. However, the timing for different rates of rise for the different scenarios                  was updated based on new modeling and more realistic assumptions of Greenland and Antarctic ice sheet                  behavior based upon the Intergovernmental Panel on Climate Change Sixth Climate Assessment. A result                  is that there is less acceleration in the higher scenarios until about 2050 and greater acceleration                  toward the end of this century. This has two primary implications. First, despite maintaining the same                  target values and having the same range between scenarios in 2100, the range covered by the scenarios                  is smaller in the near term than in the 2017 report. Second, the likely (17th-83rd percentile) ranges                  of projections for each scenario before and after the 2100 time point used to define the scenarios are                  wider than in the 2017 report.                

                  See Section 2.2.3 of the technical                    report for more information.
11. How were these                  specific sea level scenarios made for this report? ****
A goal of the 2017 and 2022 technical reports is to examine the full range of plausible amounts of                  future global sea level rise, not just those rise amounts considered “likely.” Quantifying the                  “unlikely but possible” sea level rise response can be critical to help bound certain risk planning                  exercises. For global mean sea level, these hinge on potential physical changes in the major ice                  sheets, where possible rapid collapses would contribute to very large amounts of future sea level                  rise. These “unlikely but possible” outcomes must be acknowledged and accounted for in some types of                  planning (e.g., for major infrastructure investments that have a very long operational life cycle                  and/or are critical community lifelines.) For the 2017 report, these considerations led to the                  development of a set of global mean sea level scenarios that span the plausible range of sea level                  rise and are defined by a target value of rise in 2100. In the 2022 report, the same framework is                  adopted, and the following 2100 target values of sea level rise are used to differentiate the five                  scenarios: Low (1 foot; 0.3 meters), Intermediate-Low (1.6 feet; 0.5 meters), Intermediate (3.3 feet;                  1 meters), Intermediate-High (4.9 feet; 1.5 meters) and High (6.6 feet; 2 meters).

To create the global mean sea level scenarios and associated regional                  relative sea level values, the 2022 technical report used the last report                    in 2017 as a starting point. The scenarios from that report are                  updated with the most recent science and adopted analytical methods from                  the Intergovernmental Panel on Climate Change's (IPCC) Sixth Assessment Report, completed in 2021. The IPCC                  regularly convenes top researchers from around the world to synthesize the best available climate                  science. Both the technical report and the IPCC Sixth Assessment Report draw upon the latest sea level                  rise science. Because both reports depend upon the same underlying science, they are similar and                  consistent, but the global mean sea level scenarios lead to a different framing and structure. To                  generate the scenarios used in this report, the ensemble — or set — of projections in the Sixth                  Assessment Report that are tied to specific shared socioeconomic pathways (see Question 7) are                  filtered to identify subsets of pathways that are consistent with the scenario target values in 2100                  (i.e., 0.3 meters, 0.5 meters, 1 meter, 1.5 meters and 2 meters). As in the Sixth Assessment Report,                  these scenarios are regionalized and then provided at individual tide gauge locations and for 1-degree                  grids along the global and U.S. coastlines. The median, 17th and 83rd                  percentile values are provided for each scenario at each tide gauge and grid location.                

                  See Section 2.2.3 of the technical                    report for more information.
12. How much will                  relative sea level rise in the U.S. and in the                  different regions of the U.S. in the next 30 years? ****
Sea level along the contiguous U.S. coastline is expected to rise (considering alignment of both the                  observation-based trajectories and the scenarios in 2050), on average, 10 - 12 inches (0.25 - 0.30                  meters) in the next 30 years (2020-2050). This will vary locally because of regional factors (see                  Question 4). Rise in the next three decades is anticipated to be, on average:
-                     East coast: 10 - 14 inches (0.25 - 0.35 meters)                  
-                     Gulf coast: 14 - 18 inches (0.35 - 0.45 meters)                  
-                     West coast: 4 - 8 inches (0.1 - 0.2 meters)                  
-                     Caribbean islands: 8 - 10 inches (0.2 - 0.25 meters)                  
-                     Hawaii islands: 6 - 8 inches (0.15 - 0.2 meters)                  
-                     Northern Alaska coast: 8 - 10 inches (0.2 - 0.25 meters)                  
-                     Pacific islands, Southern Alaska coast, and other locations not listed: see Question 19 for how to                    access location-specific data                  

See Section 2.3 of the technical report                    for more information.
13. Why are the                  scenarios for the next few decades lower than they were                  in the 2017 report?  Why is there no longer an extreme scenario? ****
With each passing year, improved observations and modeling help us get a clearer picture of how and                  when sea level is changing both globally and regionally (see Questions 3 and 4). The scenarios in the                  2022 technical report are lower in the near-term decades than they were in the 2017 technical report                  because there is improved understanding of Antarctic and Greenland ice sheet dynamics (see Question                  10). This improved understanding comes from additional observations, research, modeling, and expert                  elicitation efforts that indicate sea level rise will be slower in the next few decades than                  previously projected. The 2022 technical report removes the Extreme (2.5 meter) scenario because the                  probability of this scenario is now thought to be too low to merit inclusion.

                  See Section 2.2.3 and 2.3 of the                    technical report for more information.
14. Why are the                  global scenarios for 2100 the same in the 2022 and 2017 reports,  but tide gauge specific                  scenarios are considerably lower in some regions in 2100 than they were in 2017? ****
Since 2017, scientists have worked hard to study and develop better modeling of both Greenland and                  Antarctic ice sheets, and of how these two ice sheets generate different sea level changes across the                  globe because of how ice mass loss results in changes in gravitational, rotational, and deformation                  effects. The combination of these effects is referred to as “fingerprinting,” and Greenland and                  Antarctic ice sheets have very different “fingerprints” (see Question 4). Locations far away from a                  sheet see greater amounts of sea level rise when ice mass is lost from that sheet, so it really                  matters which sheet is melting, how much, and when. The 2022 report uses the latest science and                  multiple methods to characterize ice sheet processes in both Antarctica and Greenland, and the result                  is a more realistic projection of global mean sea levels over time. Due to improved characterization                  of Greenland’s potential increased contributions for the higher scenarios (Intermediate to High), this                  change results in projections of less rise along many U.S. East and Gulf locations through 2100.                  However, it is important to keep in mind that sea levels will continue to rise after 2100; the new                  projections just indicate we have more time to prepare.
15. Will sea                  level scenarios continue to change? ****
Sea level scenarios will continue to be refined as scientists increasingly observe and learn more                  about the details of dynamic earth system processes (e.g., Antarctic ice sheet response to temperature                  increases.) Additional data will help to reduce uncertainty. U.S. federal agencies monitor and assess                  key sea level rise source contributions globally and along U.S. coastlines, and this work can provide                  early indications of change in the trajectory of sea level rise, which can inform shifts in adaptation                  planning.

The 2022 technical report further refines and narrows the possible range of scenarios from the 2017                  report. Assessment reports like this are the best resource for staying up-to-date on the latest                  changes to the sea level rise scenarios and why those changes have occurred. These reports are                  anticipated about every five years.
Observation-Based Extrapolations and Extreme Water Levels16. What are                  observation-based extrapolations and what do they tell us?****
Observation-based extrapolations, or sea level rise “trajectories,” are estimates of relative sea                  level rise out to 2050. These are built by analyzing regional sets of tide gauge data. To create them,                  the rate and acceleration of sea level rise from 1970 to 2020 is calculated from sea level rise                  observations from regional sets of tide gauges. Filtering is done to remove some effects of natural                  variability that can bias trend characterizations, such as El-Nino/La-Nina cycles. For the global sea                  level rise extrapolation, satellite-based water elevation data (altimetry) was also included.                

Included in the 2022 technical report for the first time, observation-based extrapolations are                  provided for global sea level and eight coastal regions (the Northeast, Southeast, Eastern Gulf,                  Western Gulf, Southwest, Northwest, Hawaiian Islands, and the Caribbean). Separate extrapolations are                  also provided for the southern and northern coasts of Alaska and the Pacific islands but caveated with                  greater uncertainty due to variations in land elevation and underlying regional sea level rise                  processes.                

These observation-based extrapolations are very similar to the model-based projections through 2050,                  and therefore serve as a further line of evidence for the confidence in the near-term trajectory of                  sea level rise. Or, put another way, with continued global heating that is expected, there is strong                  reason to suspect that the current acceleration in sea level rise will continue, and this response is                  similar in both the observation trends and the modeled scenarios.                

                  See Section 2.2.4 of the technical                    report for more information.
17. What are                  extreme water levels as used in this report?****
The technical report uses the term extreme water levels to refer to water levels experienced during a                  wide range of flooding events, from common events that happen ten times a year to rare events such as                  a flood with a 1% annual chance of occurring. The extreme water levels are used to assess current and                  future flood exposure within the coastal floodplain considering future sea level rise using NOAA’s                  height-severity categories of minor, moderate, and major high tide flooding.

In addition to long-term sea level rise, many different physical processes can affect coastal water                  levels on much shorter time scales, such as winds and storm surge, tides, and waves. Extreme water                  levels in this report are specifically those measured by NOAA tide gauges in mostly protected areas,                  and therefore reflect still water levels without direct wave influences. The extreme water levels                  generally relate to when coastal water levels exceed specific elevation thresholds related to local                  flooding hazards. These elevation thresholds are often reflective of flooding events ranging from                  bathtub-like “nuisance” flooding that is tidally driven to destructive storm-surge flooding whose                  impact footprint is specific to that storm.                

                  The extreme water levels as defined in this report have probabilities, or likelihoods, of occurring in                  a given year that are based on statistical analysis of regional sets of historical tide gauge                  measurements, called a regional frequency analysis. Results based on regional frequency analysis                  typically suggest that higher water levels are more probable than results based upon a single tide                  gauge data record. This is because regional sets of data observation better capture spatially the                  overall probability of a high-water event occurring from a passing storm. The perspective from a                  single gauge can be rather limited due to storm track variability (storm missed the tide gauge) or                  short data records (important storms occurred prior to the gauge installation).                

                  The regional frequency analysis extreme water level probabilities are different from those produced                  and used by FEMA, since FEMA-based estimates often include synthetic storm simulations (i.e., consider                  storms that could happen under today’s climate but might not yet have happened) and high water marks                  not necessarily directly measured by a local tide gauge. The different methods produce different                  probabilities for low frequency flooding (e.g., a 100-year flood), but for more frequent events such                  as high water levels occurring every few years, the two sets of probabilities are quite similar.                

                  See Section 3                    of the technical report for more information.
18. What does                  the extreme water level frequency information in the report tell us?  What does it mean when the                  report says there will be a “flood regime shift” by 2050?****
This report considers extreme water levels that span from rare events (1% annual chance of occurring)                  to more common events (10 times/year). Specifically, the extreme water levels are used to assess                  current and future flood exposure within the coastal floodplain considering future sea level rise                  using NOAA’s height-severity categories of minor, moderate, and major high tide flooding. NOAA high                  tide flooding thresholds broadly define water levels where U.S. infrastructure becomes impacted. High                  tide flooding heights are calibrated to impact levels used in weather forecasting to trigger emergency                  responses and are considered the best tangible way to communicate the impacts of extreme water levels                  today and in the future to the public. Minor high tide flooding, flooding about 2 feet (0.6 meters)                  above average high tide, is disruptive to communities where it occurs (e.g., stormwater backups and                  road closures), whereas moderate flooding, about 3 feet (0.9 meters) above average high tide, tends to                  cause more damage (e.g., to homes or businesses) and major flooding, which is about 4 feet (1.2                  meters) above average high tide, is often quite destructive, requiring post-event repairs/rebuilding                  and sometimes evacuations.                

The report explores how the annual frequencies of high tide flooding are expected to change by 2050                  considering the local sea level rise scenario that closely aligns with the rise associated with the                  regional observation-based extrapolations. The concept of a flood regime shift is used to describe how                  the annual flood frequency associated with a particular coastal flood type (i.e., NOAA minor,                  moderate, and major high tide flooding) changes to that of another because of sea level rise. For                  example, by 2050 the annual frequency of NOAA moderate high tide flooding is expected to occur on                  average along the U.S coastline at a frequency greater than the NOAA minor high tide flooding events                  occur today. Or put another way, after about 1 foot (0.3 meters) of sea level rise that is expected to                  occur on average along the U.S coastline, tides and storm surges that today cause minor and moderate                  high tide flooding will cause moderate and major high tide flooding.                

                  See Section                    3.1 of the technical report for more information.
Accessing Data and Applying Sea Level Rise Information to          Decision-Making19. How do I                  get the sea level data for my community/location?****
Federal agencies have been updating tools with the new sea level rise                  information, and will continue to do so. The following links include access                  to report data and updated tools:
-                     Visualize community-level impacts from sea level rise and coastal                    flooding on  **NOAA's Digital Coast Sea Level Rise                        Viewer** .                  
-                     Visualize the updated scenarios and the new extrapolated observations                    data, as well as download the data, for global, regional, or individual                    tide gauges on  **NASA's Sea Level Change                        Portal** .                  
-                     Generate reports with current and future flooding impacts on stormwater                    systems with  **NOAA’s Adapting Stormwater                        Management for Coastal Floods**  tool.                  
-                     View accessible charts and graphs with sea level rise data for a                    specific coastal county on  **NOAA’s Coastal County Snapshot**  tool.                  
-                     Access and download sea level rise observation data, trends and                    projections at specific tide gauges on  **NOAA’s Sea Level                        Rise API URL Builder** .                  
- Download three datasets – Scenarios of Future Mean Sea Level (2000                    - 2150), Extreme Water Levels: Tide Gauges, and Extreme Water Levels:                    Gridded – from the 2022 technical report  **data and tools**  page.                  
20. How do I apply                  this data?****
                  A companion Application Guide is available to help users apply and integrate the report into local planning and adaptation decisions. The guide, penned by professionals with expertise on applying sea level rise to local level planning, helps readers wade through considerations and arrive at what’s best for their community. We also have several additional resources available for understanding and applying the updated sea level rise projections.                
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