Sea levels are rising, and science shows they will continue to rise for generations due to heat-trapping emissions that have already been released. This highlights a profound and enduring climate injustice: future generations will face the consequences of today’s decisions. The effects of these emissions are already unfolding, but the full extent of their impact—on coastlines, communities, and ecosystems—will play out over lifetimes to come.
Understanding sea level rise as a long-term, multi-generational problem is essential to comprehending the scale of climate change and the need for bold action now. While this knowledge may be sobering, it underscores the importance of reducing emissions, holding major polluters accountable, and adapting to a changing world. Let’s explore what is driving this persistent rise and what it means for our collective future.
What do we know about future sea level rise?
Sea level rise is one of the most well-documented and predictable consequences of climate change, with models showing that average sea levels will increase over time, even in optimistic versions of the future. Scientists use computer models, such as climate models, ice sheet models, and sea level models, to make projections of future climate change. Projections of sea level rise, such as those contained in the Intergovernmental Panel on Climate Change (IPCC) 6th Assessment Report, give us an idea of what might happen in the future.
These projections are usually based on a combination of two things: the heat-trapping emissions that have already occurred in the past and those that could occur in the future.
The future trajectories are based on different scenarios, such as versions of the future where the world comes together to take action and phase out fossil fuels, or versions where fossil fuel production continues throughout this century. These different future scenarios, combined with what we already know happened in the past, give us a range of possible future sea levels.
Most simulations focus on the near-term impacts by 2100, but some look forward multiple centuries to 2300, and occasionally some look even farther into the future, looking ahead 2,000 or even 10,000 years.
Even in the most optimistic scenarios, where global average temperatures are kept below 1.5°C, model projections show that sea levels could still rise by approximately 11-22 inches higher than present by 2100. This would cause dramatic changes in island and coastal communities. Looking further into the future, the impact is even larger. Over the next 2,000 years we could see sea levels rising as much as 7.5-10 feet. Over the next 10,000 years, as much as 20-23 feet. If the world surpasses 1.5°C of warming and instead warms by 2°C the world could endure even worse outcomes with sea levels rising 7-20 feet over 2,000 years and 26-43 feet over 10,000 years.
Looking at future sea level rise in this way gives us a combined look at the impact of both past and possible future emissions. But what if we want to know the impact of past emissions separated from the impact of future emissions? For that, we need to separate the impact of emissions that occurred over different time periods, and we need to understand the processes that make sea level rise such an enduring challenge.
What causes sea level rise to persist for centuries?
Because of the way the climate and ocean systems respond to heat-trapping emissions, sea levels will continue to rise even after air temperatures stabilize. This has been noted as a source of climate injustice, due to the profound impacts on future generations and low-lying coastal communities.
The way air temperature responds after emissions cease is called the zero emissions commitment, or ZEC. Research with climate models in recent years shows that when carbon dioxide emissions stop, the rise in atmospheric temperatures will likely also stop. This means that there would be no additional warming of the atmosphere from carbon dioxide itself, but the many complex systems on Earth will continue to respond to the heat already trapped.
So, even in a future scenario where the world achieves the stabilization of air temperatures, the Earth’s oceans and cryosphere (frozen regions like Antarctica) will continue to adjust. The oceans absorb much of the carbon dioxide lingering in the atmosphere, which contributes to ocean acidification. Meanwhile, increased atmospheric and ocean temperatures cause glaciers and ice sheets to melt and oceans to expand.
The two dominant contributing factors to rising sea levels are:
- Thermal Expansion: As the oceans absorb heat, the water expands, accounting for a significant portion of current sea level rise.
- Melting Land Ice: When global mountain glaciers and the ice sheets in Greenland and Antarctica melt, they add mass to the ocean. The combined melt of all land ice is currently the dominant driver of sea level rise, and this trend is expected to continue into the future.
Given that air temperatures stabilize when heat-trapping carbon dioxide emissions stop, yet sea levels continue to rise, we might then ask, what is the zero emissions commitment for sea level rise? How much would sea levels rise in the future just due to the impact of heat-trapping emissions that have already occurred in the past?
Delaying emissions reductions leads to higher long-term sea level rise
Scientific answers to these questions are just beginning to emerge. A few studies give us insight into the committed sea level rise that can result just from emissions that have already occurred in the past. One team found that emissions just up until 2016 could lead to approximately 2.3–3.6 feet of sea level rise by 2300—even if no other emissions happened after 2016. For reference, averaged across the Earth, sea levels have risen about 8 inches since 1901, meaning the full impact of past emissions has yet to materialize in our oceans and that future sea level rise in the coming centuries just from emissions that occurred before 2016 will exceed what we’ve experienced to date.
Another study looks at how delays in reducing heat-trapping emissions impact sea level rise across centuries. They find that for every five years that the world delays the reduction of carbon dioxide emissions, we commit the future to a median level of an additional 8 inches of sea level rise at 2300.
Ice sheet tipping points: A critical threat
Ice sheets have the potential to become the dominant factor in long-term sea level response.
One of the biggest challenges with ice sheets is that they are considered tipping elements—meaning that they can pass a threshold beyond which large scale mass loss becomes effectively irreversible on human-relevant time scales. This is especially true for the marine-based ice sheets in Antarctica, which are undergoing ice loss due to warm temperatures in both the air and the ocean. While the precise warming threshold for ice sheet tipping points is still unclear, research on times in Earth’s history where the ice sheets underwent enormous changes tells us that it could happen even at a temperature rise of around 1.5-2°C above the preindustrial average.
That’s why climate scientists are sounding the alarm—because global efforts under the Paris Agreement to keep warming below those levels are far off track. Current pledges countries have made under the Paris Agreement are projected to lead to around 3°C of atmospheric warming by the end of the century, which means we are at risk of triggering irreversible ice sheet tipping points.
Understanding these processes underscores the critical need for immediate and sustained global action to reduce emissions. Strong action to reduce heat-trapping emissions now can protect the ice sheets and limit long-term sea level rise. But the longer we delay, the greater the risk of crossing irreversible tipping points and exacerbating the impacts of sea level rise for centuries to come.
Act now to reduce impacts later
The multi-century impacts of sea level rise underscore the urgency of phasing out fossil fuels and holding major polluters accountable for their role in driving climate change. While we cannot undo the impacts of past emissions, we can limit additional damage by taking bold action now. Understanding the science behind long-term sea level rise empowers policymakers, advocates, and communities to demand accountability and push for equitable solutions to this intergenerational crisis.
This concept of long-term sea level response serves as the foundation for ongoing research that quantifies the multi-century impacts of emissions from specific industries, paving the way for informed decision-making and climate accountability.
We already see coastal communities around the world struggling to cope with flooding, storm surges, and salty ocean water contaminating freshwater reservoirs. But as enormous as the burden to adapt to present problems is, these changes are small compared to the extent of adaptation that will be needed as sea levels continue to rise.
People around the world are speaking up and calling for action. World’s Youth for Climate Justice has spoken out about the intergenerational issue of rising sea levels. The Alliance of Small Island States has been working diligently for 30 years to get the world to address the climate injustices of sea level rise.
Court cases are being filed to demand action. This past summer, the International Tribunal for the Law of the Sea (ITLOS) issued an Advisory Opinion stating that heat-trapping emissions constitute pollution of the marine environment which drives sea level rise. The court noted that nations have obligations under international law to reduce this pollution. Taking action to phase out fossil fuels is not only the right thing to do, it is a requirement under international law.
We know that sea levels will continue to rise for hundreds to thousands of years, but to what degree is not yet set in stone. We know that heat-trapping emissions must decline and reach zero as soon as possible. And what we need now is for world leaders to fulfill their legal obligations and act now for the sake of future generations.