Sea level rise projections for 2100
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Global Mean Sea Level Rise Projections for 2100
Projections for global mean sea level (GMSL) rise by 2100 vary depending on greenhouse gas emission scenarios and modeling approaches. Under a low-emissions scenario (RCP 2.6), experts estimate a likely GMSL rise of 0.30–0.65 meters by 2100, while under a high-emissions scenario (RCP 8.5), the likely range increases to 0.63–1.32 meters 12. These projections are relative to the 1986–2005 baseline.
High-Emissions and Upper Limit Scenarios
For the highest emission scenarios, there is a significant chance that sea level rise could exceed the upper bounds of previous major assessments. Experts estimate a 42–45% likelihood that GMSL rise will surpass the 0.98 meter upper bound set by the IPCC Fifth Assessment Report for RCP 8.5 12. Some studies suggest that rises larger than 1.8 meters are less than 5% probable, with an upper limit of about 1.8–1.9 meters by 2100 based on both expert opinion and process-based models . However, these upper limits are not definitive due to uncertainties, especially regarding the potential rapid loss of Antarctic ice 36.
IPCC and Probabilistic Projections
The IPCC’s Fifth Assessment Report (AR5) reported a “likely” range of 0.52–0.98 meters by 2100 for the highest emission scenario (RCP 8.5), but acknowledged that higher rises are possible if Antarctic ice sheet instability occurs . More recent perspectives argue that outcomes above the IPCC’s likely range are more probable than outcomes below it, especially under strong warming scenarios . Probabilistic projections highlight that relying on a single probability distribution may understate the true uncertainty, and that a range of outcomes should be considered for planning .
Drivers and Uncertainties in Sea Level Rise
The main driver of future sea level rise is anthropogenic greenhouse gas emissions, with natural factors like solar and volcanic activity contributing only a small fraction (up to 5%) . The largest uncertainties in projections stem from the potential for rapid ice loss from Antarctica, particularly due to marine ice cliff instability, which could significantly increase upper-end estimates 1210.
Component Contributions: Thermal Expansion and Ice Melt
Thermal expansion of ocean water (thermosteric sea level rise) is a major contributor, with projections of about 19–27 centimeters by 2100 depending on the emissions scenario . However, mass loss from glaciers and ice sheets is now a larger annual contributor than thermal expansion, and its future response to warming is less certain . Semi-empirical models, which relate sea level rise to global temperature increases, project a rise of 0.5–1.4 meters by 2100 above 1990 levels .
Extreme Sea Level Events
By 2100, extreme sea level events (such as storm surges combined with high tides and sea level rise) could reach a global coastal average of 4.2 meters, with some regions experiencing even higher extremes. Up to 90% of the increase in extreme sea levels is driven by future sea level rise, not changes in storm surges or waves .
Conclusion
By 2100, global mean sea level is projected to rise between 0.3 and 1.3 meters under most likely scenarios, with a small but non-negligible chance of rises approaching or exceeding 1.8 meters, especially if Antarctic ice loss accelerates. The main driver is human-caused greenhouse gas emissions, and the largest uncertainties are linked to ice sheet dynamics. For coastal planning and risk management, considering the full range of possible outcomes—including low-probability, high-impact scenarios—is essential 1236+2 MORE.
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Estimating global mean sea-level rise and its uncertainties by 2100 and 2300 from an expert survey
Experts project global mean sea-level rise of 0.30-0.65 m by 2100 and 0.54-2.215 m by 2300, with a 42% chance of exceeding the upper bound of the Fifth Assessment Report's range.
Estimating global mean sea-level rise and its uncertainties by 2100 and 2300 from expert assessment
Experts project a likely global mean sea-level rise of 0.30-0.65 m by 2100 and 0.54-2.215 m by 2300, with a 42% chance of exceeding the upper bound of the IPCC Fifth Assessment Report.
DOI
Future sea level rise dominates changes in worst case extreme sea levels along the global coastline by 2100
By 2100, 45% of global coastline will experience extreme sea levels above 4.2 meters, with up to 90% driven by future sea level rise, resulting in a 100-fold increase in frequency of these events.
Probabilistic Sea Level Projections at the Coast by 2100
Recent developments in probabilistic projections of coastal mean sea level rise by 2100 show uncertainties, highlighting the need for caution when using these estimates for infrastructure design and land use planning.
Twenty-first century sea-level rise could exceed IPCC projections for strong-warming futures
The IPCC's sea-level range for 2100 under strong warming is low, but outcomes above this range are more probable than below it, and decision makers may benefit from reframing IPCC's terminology to avoid unintentionally masking worst-case scenarios.
DOI