Carbon dioxide and other greenhouse gases (GHGs) are responsible for global warming, the long-term worldwide average warming experienced since the industrial revolution. GHGs arise from human use of fossil fuels for energy. Major emitters of GHGs include both industrialized countries and, in recent decades, developing countries as well. Higher global temperatures cause the extremes of hot and cold, and wet and dry, weather of recent years. This blog examines global warming and its effects.
See the Tabbed Pages for links to video tutorials, and a linked list of post titles grouped by topic.
This blog is expressly directed to readers who do not have strong training or backgrounds in science, with the intent of helping them grasp the underpinnings of this important issue. I'm going to present an ongoing series of posts that will develop various aspects of the science of global warming, its causes and possible methods for minimizing its advance and overcoming at least partially its detrimental effects.
Each post will begin with a capsule summary. It will then proceed with captioned sections to amplify and justify the statements and conclusions of the summary. I'll present images and tables where helpful to develop a point, since "a picture is worth a thousand words".
Wednesday, July 9, 2014
Sea Level Rise: Mitigation and Adaptation in the Risky Business Model
level rise is caused by expansion of ocean water as the world’s temperature
rises, and by net melting of glaciers, ice sheets and ice shelves.Ice will continue melting as long as the
temperature remains above the freezing point.
Sea level rise is
already impacting coastal cities in the U. S. and elsewhere.Regular flooding based on high tide schedules
is now happening, for example, in South Florida
and Norfolk, VA.
project future increases in sea level rise in all scenarios examined, for
modeling as distant as 300 years from now.This will clearly damage coastal cities around the world, inflicting
major property damage and requiring extensive, expensive renovation projects.
The recent report
by the Risky Business Project advocates taking a business-oriented risk
assessment approach to global warming.As applied to the occurrence of sea level rise, risk management involves
assessing harms and evaluating investments in both adaptation to continued sea
level rise and mitigation of continued global warming.Such investments would benefit people by
protecting them from future harms arising from sea level rise, and by expanding
economic activity from new projects undertaken.
earlier postprovided a tutorial
explaining the sources of global sea level rise (SLR).One important factor is the increase in volume that the waters of the
oceans occupy as their temperature increases.Since the oceans are contained, the only way to accommodate the increased
volume is to expand upward, contributing to SLR.The
second significant contribution comes from melting of ice that originates from
a land-based source.Glaciers and ice
sheets, exposed to air on their upper surfaces, melt whenever the air temperature
is higher than the melting point of water.Ice shelves, driven from land-based ice sheets to float on the ocean,
melt from below whenever the sea water temperature is above its freezing
from temperature-caused expansion of the oceans proceeds as long as the ocean
temperature continues increasing.It
will cease if the ocean temperature stabilizes.The contribution from melting reflects the temperature with reference to
the melting point of the ice.This
contribution continues to add new liquid water to the oceans as long as the
temperature of air, or of the ocean, is above the melting point of the
ice.This process continues undiminished
even when the air temperature or the ocean temperature stabilizes at a value
higher than the melting point.
Sea level rise
is already affecting the U. S.
Florida.On March 19, 2014 the (U. S.) PBS NewsHour broadcast a news feature on ocean flooding in South Florida.The frame below, taken from the broadcast,
shows a street in Miami Beach, a municipality built on a barrier island facing
the Atlantic Ocean, flooded with ocean water on a sunny day.
Such events have
occurred with some regularity in recent years.The broadcast included an interview with Prof. Hal Wanless, of the University of Miami, who ascribes these events to worsening sea
level rise.It reported that the U. S.
Army Corps of Engineers predicts a 3-7 in. (7.6-18 cm) rise in sea level for South Florida by 2030, and 9-24 in. (23-61 cm) by 2060.
In response, the
Miami Beach Public Works Department initially planned a US$200 million
remediation program over the next 20 years to fend off flooding and
encroachment by the ocean.Recently the municipality of Miami Beach agreed to double its investment, to US$400
million.More broadly, a four-county consortium
in the area is planning a concerted program to address the expected sea level
rise.The local politicians are
grappling with the political pressures opposing the extensive investments needed
to prepare for the expected worsening of the problem.
A conference in
June 2012 on the effect of global warmingfocused on the projected loss of land area in
South Florida over the next century due to sea level
rise.It is foreseen that the Florida
Key islands would be lost, and that Miami and the surrounding area would be small
islands in the encroaching Atlantic
Ocean.The report notes that this area has the most
people and property endangered by sea level rise of any in the U. S.
Norfolk, Virginia.Norfolk is at the confluence of the Atlantic Ocean, Chesapeake Bay and the James
River.It is the site of a major base of the U. S.
Navy which is a principal driver of economic activity in the region.The area has been subjected to continued
episodes of tidal flooding along its coastline.In a report on the PBS Newshour in December 2012
its mayor, Paul Fraim noted that the city is repeatedly flooded at high tides,
which is worsening with passing time.The
screen shot below shows a home that been repeatedly flooded in recent times.
Still frame from
PBS Newshour broadcast on sea level rise affecting NorfolkVA.The photo shows the
home of Bob Parsons, who has documented the many times flooding has affected
The mayor stated
that parts of the city might not be habitable in 15 years, and that the city is
already renovating impacted areas by raising home structures to higher levels,
and raising roads.Relocation to higher
ground is also envisioned.The U. S.
Navy is replacing 14 piers because of rising water at a cost of US$490-560
The Washington Post
that according to the U. S. National Oceanic and Atmospheric Administration,
Norfolk, together with a 600 mile section along the U. S. East Coast, is a “sea
level rise hotspot”, with SLR
expected to be 3-4 times the worldwide average.Much of this is due to a change in the Atlantic Ocean Gulf Stream that
directs more water toward the U. S. eastern shore.Norfolk in addition is slowly subsiding into the
sea due to geological factors.A
Virginia study projects that SLR
in the Norfolk area could be 5 ½ feet (1.68 m) by the end of this century if
the world does not institute mitigation measures to curb global warming.
The report states
that Norfolk engaged a Dutch firm to design an
adaptation plan to protect the city.The
resulting project, involving new flood gates, building higher roads and
renovating the storm sewer system would protect against water 1 foot (31 cm)
higher, and cost US$1 billion, more than the city’s current annual budget.
Sea Level Rise
Around the U. S.An interactive map of coastal and tidal
regions susceptible to ocean flooding around the U. S. shows the increasing loss of land area as
the sea level rises between 1 foot and 9 feet (30 cm and 274 cm).
Projections of future SLR show severe further effects to the year 2100, and the
year 2300.Schaeffer and coworkers
(Nature Climate Change 2012; DOI: 10.1038/NCLIMATE1584)
developed projections based on the warming trajectories arising from several
scenarios for emissions of greenhouse gases.These range from a continued annual emissions rate in an essentially
unconstrained scenario to one with a hypothetical stringent reduction to a zero
emissions rate in 2016.Their results
are summarized in the following graphic.
Projected sea level
rise under various greenhouse gas emission scenarios, ranging from
unconstrained (CPH reference) to stringent reduction to zero
emissions in 2016 (Zero 2016).The
colored bands give full uncertainty values within the graphic, and the shaded
bars to the right, for only two cases, the lowest and highest SLR projections.Note that the time axis (horizontal) and the SLR axis (vertical) use different scales in a
and b.a, Projections for
2000-2100; the vertical scale runs to about 43 in. b, Historical data
from 1000 to 2000, and projections from 2000 to 2300 with the vertical gray
shading showing the present 21st century; the vertical scale runs to
about 13 feet.
The results of
Schaeffer and coworkers reflect in numbers the notions expressed in the
Introduction; namely, that as long as the global temperature operates to keep
temperatures over land ice, and under ocean-based ice shelves, above their
melting points, ice will melt and contribute to further SLR.Temperature-induced expansion of the oceans continues in scenarios with
continued emissions of greenhouse gases (the upper projections in the
graphics), but this writer presumes that this contribution is reduced in
scenarios with limits on emissions (lower projections in the graphics).And since global temperature depends on the
total accumulated level of greenhouse gases in the atmosphere, the temperature
cannot go back to lower values, low enough to keep ice sheets and ice shelves
frozen.In contrast, panel b in
the graphic above shows that sea level was essentially unchanged from the year
1000 until the beginning of the industrial revolution when humanity began
burning fossil fuels.
The recent Risky
highlights the important role that risk analysis can play in planning future
responses to global warming.The effects
of warming can be viewed as shifting a probability curve giving the likelihood
of occurrence of an extreme event with major damaging effects “to the right”,
i.e., in the direction of higher likelihood of occurrence.An example drawn from the topic of this post
could be an extreme effect from sea flooding due to rising temperatures.Such disasters wreak significant
socioeconomic hardship on those affected.The report suggests that risk management could develop programs for
investing in infrastructure to minimize future risk.
The risk of
harms from SLR is extremely high, according to the model projections shown
in the graphic above.In the framework
of the Risky Business report, risk management under these circumstances leads
to the conclusion that investments to help mitigate further warming, as well as
adaptive investments to strengthen infrastructure to withstand SLR, are both warranted.Risk management should be adopted worldwide,
since global warming is a universal phenomenon involving all nations that emit
greenhouse gases, and the effects of SLR likewise are felt worldwide.
The risks arise because around the world, many cities
are situated along coastlines, and as countries develop their populations tend
to leave rural settings and gravitate to their cities.Among developed countries also, many cities
are in coastal settings.
Focusing on the U. S., the examples of regular inundations from
the ocean, described above, are not exceptional.SLR aggravates tidal flooding, and sets the
stage for more damaging storm surges in extreme weather events.The financial costs of such damages are very
large, and are met from public coffers and private risk insurance.Both these coverages will increase as SLR worsens.
Risk management entails investments that would both
minimize further warming and protect against damage when SLR threats are present.Such investment would help lower future
damage costs, and contribute significantly to the economy by increasing
employment in the industries involved.Thus
the risk management evaluation of SLR and its attendant damages leads to
activities that minimize future harms to coastal communities and expands
economic growth.Both of these outcomes
are highly desirable.