New research predicts that by 2100, damage from flooding and rising seas could cost the world almost a tenth of its economy.
The paper, by researchers at the University of Southampton, modeled the economic effects of future sea level rise, using various projections from the Intergovernmental Panel on Climate Change (IPCC) of future carbon emissions and global warming, along with various models of future economic growth, population growth, and population movement.
According to the IPCC’s projections, sea level will rise 25 to 123 centimeters, depending on whether humanity does a lot to tackle climate change or just coasts along with business-as-usual. Using those models, the researchers concluded 0.2 to 4.6 percent of the world’s population will be flooded annually by the end of the century, resulting in annual losses of 0.3 to 9.3 percent of global GDP.
For reference, 5 percent of the world’s population in 2100 could mean 600 million people — many of whom will live in deeply impoverished regions like southern Asia. As for GDP, 9.3 percent of that could be over $100 trillion.
The researchers also looked into scenarios in which people around the world attempt to protect themselves and their coasts by expanding dikes, levees, and other protection systems. The paper concludes such efforts could reduce the damage from flooding by two or three orders of magnitude, at a cost of $71 billion per year under the most demanding circumstances.
“If we ignore sea-level rise, flood damages will progressively rise and presently good defences will be degraded and ultimately overwhelmed,” said Professor Robert Nicholls, one of the paper’s co-authors. “Hence we must start to adapt now, be that planning higher defences, flood proofing buildings and strategically planning coastal land use.”
Other efforts at flood mitigation and adaptation can include resorting to wetlands and beaches as natural barriers, and better city planning. In the wake of Sandy and other major storms, American cities like New York, Houston, and Miami are prepping new drainage systems, conservation efforts, zoning changes, and infrastructure improvements. The entire state of Massachusetts is undertaking a similar project.
“This long-term perspective is however a challenge to bring about, as coastal development tends to be dominated by short-term interests,” Nicholls added. “For example, real-estate and tourism companies, which prefer to build directly at the waterfront with little thought about the future.”
That huge difference between the costs of action versus inaction is also reflected in most of the work on climate change as a whole. A 2006 assessment by Lord Nicholas Stern, under the auspices of the British government, determined climate change could eventually reduce the world’s economy five to twenty percent annually. Stern later said that, in light of new evidence, the report probably undershot the damage. (The original report also said that by mid-century, as many as 200 million people around the world could be displaced by flooding.)
“If we do not reduce greenhouse gases swiftly and substantially, some regions will have to seriously consider relocating significant numbers of people in the longer run,” said Jochen Hinkel, the lead author of the Southampton paper.
It could also get worse. The University of Southampton work doesn’t take account of several factors that could worsen the damage: changing cyclone activity due to climate change and other natural influences, as well as sinking land thanks to groundwater, oil, and gas extraction. A December paper from James Hansen and other prominent climate scientists and economists also suggested the IPCC is significantly low-balling climate change’s threat this century. Their numbers say sea level rise could be several meters.
On top of all this, simply relying on dike and levee protection rather than a full-on global press to cut carbon emissions could make matters worse. “If you build dikes, people feel safe and move into the exposed area and that increases the amount of infrastructure,” Bob Kopp, a Rutgers University climate scientist not affiliated with the study, warned reporters. “If your dikes slip up, you increase your losses even more.”