A composite sketch of rising seas

A RECENT STUDY by researchers at Rutgers University and Nanyang Technological University in Singapore have found that sea levels may rise as much as 2.4 metres by 2100 and a further 15.5 metres by 2300.

The research, published in the Annual Review of Environment and Resources, is a composite of numerous recent estimates used to make short- and long-term projections for global sea level rise. It also incorporated data used to reconstruct historic changes in sea levels.

Rutgers and NTU researchers projected best and worst case scenarios that fluctuate based on how carbon emissions are expected to change. Though estimates vary depending on how projections are calculated, a clear trend towards both short- and long-term sea level increases exists.

And the changes are already underway. Between 2000 and 2050, an increase of 0.1 to 0.5 metres is very likely, they found, though estimates beyond that are harder to figure out because of uncertainty over future levels of greenhouse gas emissions.

“There’s much that’s known about past and future sea level change, and much that is uncertain. But uncertainty isn’t a reason to ignore the challenge,” says Robert E. Kopp, study co-author and a professor in the Department of Earth and Planetary Sciences at Rutgers University-New Brunswick. “Carefully characterizing what’s known and what’s uncertain is crucial to managing the risks sea level rise poses to coasts around the world.”

Historic shifts

Sea levels have been rising alongside warming planetary conditions since the late 1800s when humans began burning coal and other fossil fuels in large quantities for energy. Though the measurements seem small, the rate at which sea level are rising has increased in recent years.

And the amount has been adding up over time.

There’s much that’s known about past and future sea level change, and much that is uncertain. But uncertainty isn’t a reason to ignore the challenge. 

Between 1900 and 1990, sea level rose by 1.2 to 1.7 millimetres each year – though today, this rate has increased to 3.2 millimetres annually. Most of the change, especially in the last quarter of the twentieth century, is a result of human-caused temperature increases. Levels are expected to continue rising more rapidly by the end of the century.

Ultimately, there are two main explanations for rising sea levels. First, warming temperatures cause water to expand, increasing the volume of the water in the oceans.

Melting ice sheets and glaciers that stream meltwater into the oceans are another primary driver of expanding oceans. These changes will be especially dire for the 11 percent of the world’s population who live in coastal areas less than 10 metres above sea level. By 2060, more than a billion people could be living in such coastal regions, threatened by rising waters that also jeopardize the integrity of global economies, infrastructure – whole ecosystems.

IPCC offers grave warning of rising temperatures

The Rutgers and Nanyang Technological University findings coincide with the recent release of a special report by the Intergovernmental Panel on Climate Change (IPCC).

Drawing on the work of thousands of scientists, experts and government reviewers worldwide, the IPCC, the United Nation’s body on climate change, detailed how a 1.5 °C in global temperatures above pre-industrial levels could affect the planet. The results are grim. Disease, drought, poverty and extreme weather events populate its pages, in addition to the potential for irreversible damages to natural ecosystems.

The report also discussed how much more dramatic the global impacts of a 2 °C rise in temperatures could be. If temperatures rise by 2 °C rather than 1.5 °C, the IPCC argued, sea levels could rise an additional 10 centimetres, spurred on by an ice-free Arctic Ocean that could happen every ten years, rather than every hundred years. Coral reefs, meanwhile, could be eradicated.

“We can keep global warming below 1.5 °C,” says Jim Skea, co-chair of IPCC Working Group III. “It’s possible within the laws of physics and chemistry, but it will require huge transitions in all sorts of systems.”

Limiting global warming to 1.5 °C would require “rapid and far-reaching” changes to energy, land, industrial, and infrastructure systems, he said. Carbon emissions would also need to be reduced by 45 percent from 2010 levels by 2030.

All pathways that limit global warming to 1.5 °C also require an effort to actively extract carbon from the air. This means removing between 100 and 1000 gigatons of carbon from the atmosphere by 2100.

Taken together, these reports have compiled valuable data for policymakers and government, urging them to take action to limit the severe impacts on environmental and human health from climate change and risings seas that we know are coming. Both show critical action is needed now.