Abstract
This report and accompanying datasets from the U.S. Sea Level Rise and Coastal Flood Hazard Scenarios
and Tools Interagency Task Force provide 1) sea level rise scenarios to 2150 by decade that include esti-
mates of vertical land motion and 2) a set of extreme water level probabilities for various heights along the
U.S. coastline. These data are available at 1-degree grids along the U.S. coastline and downscaled specifical-
ly at NOAA tide-gauge locations. Estimates of flood exposure are assessed using contemporary U.S. coastal
flood-severity thresholds for current conditions (e.g., sea levels and infrastructure footprint) and for the next
30 years (out to year 2050), assuming no additional risk reduction measures are enacted.
This effort builds upon the 2017 Task Force report (Sweet et al., 2017). In particular, the set of global mean
sea level rise scenarios from that report are updated and downscaled with output directly from the United
Nations Intergovernmental Panel on Climate Change (IPCC) Sixth Assessment Report (AR6; IPCC, 2021a),
through the efforts of the NASA Sea Level Change Team; updates include adjustments to the temporal tra-
jectories and exceedance probabilities of these scenarios based upon end-of-century global temperatures.
As with the 2017 report, these global mean sea level rise scenarios are regionalized for the U.S. coastline.
In addition, methodology supporting the U.S. Department of Defense Regional Sea Level (DRSL) database1
(Hall et al., 2016) is adapted for the extreme water level dataset newly developed for this report.
This report will be a key technical input for the Fifth National Climate Assessment (NCA5). These data and
information are being incorporated into current and planned agency tools and services, such as NOAA’s Sea
Level Rise Viewer and Inundation Dashboard,2 NASA’s Sea Level Change Portal,3 and others. Although the
intent of this report is not to provide authoritative guidance or design specifications for a specific project, it is
intended to help inform Federal agencies, state and local governments, and stakeholders in coastal communities about current and future sea level rise to help contextualize its effects for decision-making purposes.
Key Message #1:
Multiple lines of evidence provide increased confidence, regardless of the emissions pathway, in a narrower
range of projected global, national, and regional sea level rise at 2050 than previously reported
(Sweet et al., 2017).
Key Message #2:
By 2050, the expected relative sea level (RSL) will cause tide and storm surge heights to increase and will
lead to a shift in U.S. coastal flood regimes, with major and moderate high tide flood events occurring as
frequently as moderate and minor high tide flood events occur today. Without additional risk-reduction measures, U.S. coastal infrastructure, communities, and ecosystems will face significant consequences.
Key Message #3:
Higher global temperatures increase the chances of higher sea level by the end of the century and beyond.
The scenario projections of relative sea level along the contiguous U.S. (CONUS) coastline are about
0.6–2.2 m in 2100 and 0.8–3.9 m in 2150 (relative to sea level in 2000); these ranges are driven by uncertainty in future emissions pathways and the response of the underlying physical processes.
Key Message #4:
Monitoring the sources of ongoing sea level rise and the processes driving changes in sea level is critical for
assessing scenario divergence and tracking the trajectory of observed sea level rise, particularly during the
time period when future emissions pathways lead to increased ranges in projected sea level rise.