Projected sea level rise by 2100
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Projected Sea Level Rise by 2100
Global Mean Sea-Level Rise Projections
Low Emission Scenarios (RCP 2.6)
Under the low emission scenario, Representative Concentration Pathway (RCP) 2.6, experts project a global mean sea-level (GMSL) rise of 0.30 to 0.65 meters by 2100 relative to the 1986-2005 baseline . This scenario assumes significant mitigation efforts to limit global warming to below 2°C above pre-industrial levels. The median likely range provided by experts is 0.4 to 0.6 meters, suggesting a good chance to limit future sea-level rise to less than 1 meter if climate mitigation measures are successfully implemented .
High Emission Scenarios (RCP 8.5)
In contrast, under the high emission scenario, RCP 8.5, which assumes continued high greenhouse gas emissions, the projected GMSL rise is significantly higher. Experts estimate a likely range of 0.63 to 1.32 meters by 2100 . The Intergovernmental Panel on Climate Change (IPCC) Fifth Assessment Report (AR5) reported a likely range of 0.45 to 0.82 meters for the late 21st century (2081-2100) and 0.52 to 0.98 meters by 2100 . However, there is a roughly one-third probability that sea-level rise by 2100 may lie outside this likely range, potentially exceeding 1 meter if sections of the Antarctic ice sheet collapse .
Uncertainties and Upper Limits
Expert Opinions and Probabilistic Assessments
The uncertainties in sea-level rise projections are significant due to the complex processes and feedback mechanisms involved. Expert surveys indicate that there is a 5% probability that sea-level rise could exceed 1.8 meters by 2100 under the worst-case scenario . This upper limit is based on summing the highest estimates of individual sea-level rise components simulated by process-based models . Additionally, probabilistic projections suggest that relying on a single probability distribution can understate true uncertainty and potentially misinform users .
Impact of Natural and Anthropogenic Forcings
Anthropogenic greenhouse gases are the dominant forcing driving sea-level rise, with natural forcings such as solar and volcanic activity contributing minimally . Even the most intense volcanic activity from the past millennium would only reduce sea-level rise by 10-15 centimeters, highlighting the overwhelming influence of human activities .
Regional Variations and Coastal Impacts
Coastal Sea-Level Rise
Warming of 2°C will lead to an average global ocean rise of 20 centimeters, but more than 90% of coastal areas will experience greater rises . By 2100, with a 5°C rise under RCP 8.5, sea levels could rise rapidly, reaching a median of 0.9 meters, with 80% of the global coastline exceeding the 95th percentile upper limit of 1.8 meters . Coastal communities, especially in rapidly expanding cities in the developing world, will face significant challenges in adapting to these changes .
Extreme Sea Levels
Extreme sea levels (ESLs) along the global coastline are projected to increase significantly by 2100. Under a low probability sea-level rise scenario, ESLs could exceed 4.2 meters globally, with up to 9-10 meters in regions like the East China Sea, Japan, and North European coastal areas . By 2100, almost 45% of the global coastline would experience ESLs above the global mean of 4.2 meters .
Conclusion
Projections of sea-level rise by 2100 vary significantly depending on emission scenarios and the complex interplay of contributing factors. Under low emission scenarios, sea-level rise could be limited to 0.30 to 0.65 meters, while high emission scenarios could see rises of 0.63 to 1.32 meters or more. The uncertainties remain substantial, with potential upper limits exceeding 1.8 meters. Coastal regions will face disproportionate impacts, necessitating urgent adaptation and mitigation efforts to manage future risks.
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