increase was passed in reaction to projections showing Social
Security would run out of money far in the future. This is an
example of a difficult political act designed to head off problems
long after the people who passed it have left office.
Even greater political courage may be required to address another long-term problem that has the potential to cause severe
economic disruption: managing the consequence of melting ice on
sea levels across the world. As with Social Security and Medicare,
forecasting the problem requires complex modeling and many assumptions. It also involves difficult intergenerational trade-offs.
During the remainder of this century, hundreds of millions of
people and trillions of dollars of property will be threatened by
rising tides fed by melting surface ice currently trapped in glaciers
and high-latitude ice sheets. The good news is that the effects of
melting ice will materialize gradually. The bad news is that unless
we begin the process of planning for adaptation soon, there is a
high likelihood of serious economic disruption in the future.
The key problem is that we are building (and rebuilding after
catastrophes) houses, commercial buildings, and other infrastructure in coastal areas with design lifetimes of a century or
more without sufficient consideration of the future cost of protecting those assets from rising sea levels. This is a significant
issue for the United States given its wealth and concentration of
exposure in coastal areas like New Orleans, New York, or south
Florida. The government is likely to incur hundreds of billions
of dollars of costs from sources such as the National Flood Insurance Program (insurance payouts), the Federal Emergency
Management Agency (disaster relief), or the Army Corps of
Engineers (levees or other defenses) that are not currently considered in long-term budget projections. Even the Department
of Defense has concluded that numerous military installations
are at risk and will require investment in protection.
Rising Sea Levels
There has been a great deal of controversy about climate change.
Some question whether the climate is changing at all. Others
are convinced we face imminent doom unless radical steps are
taken. With regard to potential property damage, even if one accepts that the climate is changing, the effects may not be clear.
For example, consider North Atlantic hurricanes. Activity could
be increased by higher sea surface temperatures (ocean heat
fuels tropical cyclones), while it could be decreased by more
dry air from desertification of Africa (dry air suppresses thunderstorm activity).
Even ignoring any change in climate, human activity is affecting the likelihood of catastrophes from flooding. For example,
parts of many coastal cities have been built on reclaimed land,
marsh, or river deltas. The enormous weight of buildings can
cause such land to sink, increasing flood risk. Perhaps the best
example of this phenomenon is Bangkok, where a recent study
forecast a total “sea-level rise” by 2050 of 32. 3 cm, of which 20
cm is from land subsidence. Flood losses in 2050 could be 4. 25
times today’s losses, with 70 percent of the increase attributable
to land subsidence alone.
Of all the things that may or may not be occurring in the
global climate, the prospect of rising sea levels is the one that
is very hard to dispute. Both ground and satellite observations
clearly show a significant decline in ice contained in glaciers and
high-latitude ice caps in recent decades. Observed temperatures
have increased significantly in the Arctic and Antarctic. Even if
high-latitude temperatures stabilize at current levels, significant amounts of ice will melt in coming decades. Tremendous
amounts of stored water are being released, and there is only one
place that water can go: into the oceans and onto beaches. As
Steve Nerem, head of NASA’s Sea Level Change Team, recently
said, “Given what we know about how the ocean expands as it
warms and how ice sheets and glaciers are adding water to the
seas, it’s pretty certain we are locked into at least 3 feet of sea-level rise, and probably more.”