green house effect and sea level rise

8/11/2019 Green House Effect and Sea Level Rise

1/28

Green

House

Effect

and

SeaLevelRise


2/28

Overview:

- Greenhouse effect and global warming- Impact of global warming and a changing climate

- Sea level rise local, regional and global levels

- Consequences of sea level rise

- Protecting the impacts of sea level rise- Cost of establishing such protective measures


3/28

What is the greenhouse effect and how is global warming happening?


4/28

What is the greenhouse effectand how is global warming

happening?

Earths greenhouse effect is a

natural phenomenon that helpsregulate the temperature of our

planet. Sun radiation heats the

Earth and some of this heat, rather

than escaping back to space, is

trapped in the atmosphere byclouds and greenhouse gases. Schematic of the

Greenhouse Effect process
http://upload.wikimedia.org/wikipedia/commons/5/58/Greenhouse_Effect.svg


5/28

During Earths long history, climate has changed many times, albeit slowly.

Many world leading Scientists think that the climate may be changing again, as the Earths average temperature starts

to go up global warming.

Throughout the first half of the 20th century, scientists generally recognized the significance of the greenhouse effect (after

Svante Arrhenius, 1896) on global warming, but most thought that humanity was unlikely to substantially alter its impact on

climate.

The oceans contain 50 times as much CO2 as the atmosphere, and physical laws governing the relationship between the

concentrations of CO2 in the oceans and in the atmosphere seemed to suggest that this ratio would remain fixed, implyingthat only 2 percent of the CO2 released by human activities would remain in the atmosphere.

This complacency, however, was shattered in 1957 when Revelle and Seuss (1957) demonstrated that the oceans could not

absorb CO2 as rapidly as humanity was releasing it to the atmosphere by the process of burning fossil fuels for powering

cars, homes and factories.

In the last decade, climatologists have reached a consensus that a doubling of CO2 would warm the earth 1.5-4.5oC, which

could leave our planet warmer than it has ever been during the last few million years.

Moreover, humanity is increasing the concentrations of other gases whose combined greenhouse effect could be as great as

that due to CO2

alone, including methane, chlorofluorocarbons, nitrous oxide, and sulfur dioxide.

All these gases eventually trap heat somewhat like the glass panels in a green house, creating what is known as the

greenhouse effect. This leads to global warming which could have serious consequences for the planet:

- Retreation of large glaciers by melting

- sea level rise- Alteration of precipitation patterns

- change in the frequency of droughts and severe storms

- Human deaths from infections of animal and plant species, and multiple economic effects


6/28

How do we know CO2 in the

atmosphere is increasing? and that

human are responsible?Careful measurements have confirmed

that CO2 is increasing in the atmosphere

and that human activities are the prime

cause.

CO2 measurements have been taken

directly from the atmosphere over the

past few decades.

CO2 -trends for earlier times have been

derived from measurements of CO2trapped in air bubbles in glacial and

polar ice.

The 30% increase in atmosphere CO2observed since pre-industrial times cannot

be explained by natural causes.

CO2 concentrations have varied naturally

throughout Earths history.

However, CO2 concentrations are nowhigher than any seen in at least the past

450,000 years.


7/28
http://upload.wikimedia.org/wikipedia/commons/b/bb/Major_greenhouse_gas_trends.png


8/28

What human processes contribute these gases to the atmosphere, and therefore

occurrence of Greenhouse Effect?

Burning natural gas, coal and oilincluding gasoline for automobile enginesraises the level of

carbon dioxide in the atmosphere.

Some farming practices and land-use changes increase the levels of methane and nitrous oxide.

Many factories produce long-lasting industrial gases that do not occur naturally, yet contribute

significantly to the enhanced greenhouse effect and global warming.

Deforestation also contributes to global warming. Trees use carbon dioxide and give off oxygen in

its place, which helps to create the optimal balance of gases in the atmosphere. As more forests are

logged for timber or cut down to make way for farming, however, there are fewer trees to perform

this critical function.

Population growth is another factor in global warming, because as more people use fossil fuels for

heat, transportation and manufacturing the level of greenhouse gases continues to increase. As more

farming occurs to feed millions of new people, more greenhouse gases enter the atmosphere.


9/28

Is our planet warming because of

greenhouse effect?

The global temperature record shows anaverage warming of about 1F over the

past century. This warming has been

recorded in both the northern and

southern hemispheres, and over the

oceans, with some areas substantiallywarmer and others actually cooler.


10/28

Our health, agriculture, water resources, forest, wildlife and coastal areas are vulnerable to globalwarming and the climatic changes it will bring.

The climatic change is likely to have wide-ranging and most adverse impacts on human health, with

significant loss of life.

A few degrees of warming increase the changes of more frequent and severe heat waves, which can

cause more heat-related death and illness.

Greater heat can also mean worsened air pollution, as well as damaged crops and depleted water

resources

Warming is likely to allow tropical diseases, such as malaria, to spread northward in some areas of the

world.

It will also intensify Earths hydrological cycle. This means that both evaporation and precipitationwill increase. At some time, extreme events like floods and droughts are likely to become more

frequent.

Warming will cause glaciers to melt and ocean to expand from the SST increase

Sea level rise will eventually threaten low-lying coastal areas and lead to massive economic and

environment disasters

Potential impact of global warming and

a changing climate


11/28

Climate and Sea Level


12/28

Climate and Sea

Level


13/28


14/28

Denudation

(long term change due to geological processes)


15/28

Relative Sea Level Rise in USA The level of the oceans has always fluctuated with changes in globaltemperatures.

During ice ages when global temperatures were 5oC (9oF) lower

than today, much of the ocean's water was tied up in glaciers andsea level was often over one hundred meters lower than today

(Donn et al., 1962; Oldale, 1985).

On the other hand, during the last interglacial period (100,000 years

ago) when temperatures were about 1oC (2oF) warmer, sea level was

approximately 6 meters (20 feet) higher than today (Mercer,1970).

When discussing shorter periods of time, one must distinguish

worldwide (eustatic) sea level rise from relative sea level rise,

which includes land subsidence.

Although climate affects worldwide sea level, the rate of sea level

rise relative to a particular coast has more practical importance,

because some coastal areas are sinking while others are rising.

Relative sea level rise in the United States varies from more than one

meter per century in Louisiana and parts of California and Texas, to thirty

centimeters (one foot) per century along most of the Atlantic and Gulf

Coasts, to a slight drop in much of the Pacific Northwest
http://www.globalwarmingart.com/images/0/0f/Recent_Sea_Level_Rise.png


16/28

Red and white show where sea level has risen the

most rapidly. Purple and blue where it has dropped.

Global Sea Level Trend
http://www.globalwarmingart.com/images/0/0f/Recent_Sea_Level_Rise.pnghttp://en.wikipedia.org/wiki/Image:NASA_sea_level_change_trend.jpg


17/28

Global sea level trends have generally been estimated by

combining the trends at tidal stations around the world.

These records suggest that during the last century,worldwide sea level has risen 10 to 25 cm (4 to 10 in)

(Barnett, 1984), much of which has been attributed to the

global warming of the last century (Gornitz et al., 1982;

Meier, 1984).

The projected global warming could raise worldwide

sea level by expanding ocean water, melting mountain

glaciers, and causing the ice sheets of Greenland and

Antarctica to melt or slide into the oceans.

The greenhouse effect would not necessarily raise sealevel by the same amount everywhere.

Removal of water from the world's ice sheets would

move the earth's center of gravity away from

Greenland and Antarctica; the oceans' water would thus

be redistributed toward the new center of gravity.

Along the coast of the United States, this effect would

generally increase sea level rise by less than 10 percent.

Climate change could also influence local sea level by

changing winds, atmospheric pressure, and ocean

currents.

Recent estimates of sea level rise, which generally fall into the

range of 50 to 200 cm (2 to 7 feet) by 2100; Studies since 1990,

however, generally suggest that the 50-200 cm rise is more

likely to take 150-200 years.

Future Trend in Global Sea Level


18/28

Effects of Sea Level Rise

A rise in sea level would inundate wetlands and lowlands, accelerate coastal erosion, exacerbate coastal

flooding, threaten coastal structures, raise water tables, and increase the salinity of rivers, bays, and

aquifers (Barth and Titus, 1984).

We briefly describe the impacts that would result if nothing was done to address sea level rise.

This figure illustrates, the area of wetlands

today is generally far greater than the area that

would be available for new wetlands if sealevel rose too rapidly (Titus, 1986 and 1988).

Moreover, in many areas people have built

bulkheads just above the marsh; if sea level

rose, the wetlands would be squeezed betweenthe estuary and the bulkhead

Such a loss would reduce available habitat for

birds and juvenile fish, and would reduce the

production of organic materials on whichestuarine fish rely.Construction of bulkheads, dikes, and the artificial elevationof nearby developed lands would prevent new wetlands from

forming inland, resulting in a total loss in some areas

Shoreline Retreat. Coastal marshes and swamps are generally found between the highest tide of the year and

mean sea level. Because they collect sediment and produce peat upon which they can build, most wetlandshave been able to keep pace with the past rate of sea level rise.


19/28


20/28

Flooding:

Coastal areas would become more vulnerable to flooding for four reasons:

(1)A higher sea level provides a higher base for storm surges to build upon; a one meter rise in sea level wouldthus enable a 15-year storm to flood many areas that today are only flooded by a 100-year storm (Kana et al.,

1984).

(2)Beach erosion would leave particular properties more vulnerable to storm waves.

(3)Higher water levels would increase flooding due to rainstormsby reducing coastal drainage.

(4)Finally, a rise in sea level would raise water tables.

Many coastal areas are protected with levees and seawalls, and would thus not necessarily experience inundation,

erosion, or flooding.

However, these structures have been designed for current sea level.

Higher water levels would threaten the integrity of these coastal structures because

(1) higher flood levels might overtop them, and

(2) erosion could undermine them from below

Saltwater Intrusion:

Finally, a rise in sea level would enable saltwater to penetrate farther inland and upstream in rivers, bays,

wetlands, and aquifers, which would be harmful to some aquatic plants and animals, and would threaten human

uses of water.


21/28

Bay water salinity due to

Sea Level Rise


22/28

Impact of Sea Level Rise on

Island Water Table


23/28

Responses to SLR that causes Inundation,Erosion, and Flooding:

To protect the impact of SLR, there are three possible responses

that fall broadly into three categories:

- Erecting wall to hold back the sea- Allowing the sea to advance and adopting to it

- Raising the land


24/28

Protecting the impacts of Sea Level RiseFigure (below) illustrates four possible responses by which

barrier islands could respond to sea level rise:

- no protection

- engineering a landward retreat

- raising the island in place

- building a levee

A case study of Long Beach Island, New Jersey, concluded

that all three protection options are far less costly than thevalue of the land that would be threatened.

Although levees and retreat are somewhat less expensive than

raising islands, the latter option would probably be preferred

because

(1)constructing levees and seawalls would result in the loss of

beaches and waterfront views; and

(2)retreat would not be feasible for islands with high-rises

and would only be marginally less expensive for moderately

developed islands, while requiring major changes in how

people view ownership of coastal property (Titus, 1990).

Responses to sea level rise for

developed barrier islands


25/28

Protecting the impacts of Sea Level Rise

-Bulkhead to protect the property

- Prevent development to allow wetland

migrate inland


26/28

Cost of Protecting the Open Coast

In developed coastal areas of the urban region, the cost of construction for protecting the properties ismuch lower than the cost of the land.

In open coastal areas, the cost of construction is however much higher than the land cost.

Because resources are limited, we can only consider a signal technology for the entire open coast.Thus, we choose the island raising approach. This task consists of estimating

(1)the cost of placing sand on the beach profile and low parts of barrier islands, and

(2)the cost of elevating houses and infrastructure.

Sand Quantities (for the first case):

This part of the analysis requires us to estimate the amount of sand each state would require and

the average unit cost of sand in that state.

For the former task, we employ the "raise the profile" method, which is consistent with the Bruun

law (1962). This method simply states that the amount of sand required is equal to the area

being raised times the rise in sea level.

For small amounts of sea level rise, only the active beachprofile must be raised (to curtail

erosion); for larger rises, dry land must also be raised (to prevent inundation).


27/28

Based on Titus and Greene (1989) and Titus et al. (1991), the amount of sand required for two cases

low and high SLR scenarios can be estimated as follows

Low: Sandt = A

SLRt

High: Sandt = A

SLRt B

SLRt-1 + c

Sandt-1,

where, B = A

(1 - (1-c)

(di/dl)1.5)

and A is the ratio of the horizontal and vertical extents of the beach profile, 1/(1-c) is the "e-folding"

time for long-term profile adjustment in years, and (di/dl)1.5 is an estimate of the ratio of the profile

lengths from the two closure depths suggested estimated by Hallermeier.

Then the sand cost can be estimated for the quantity from the above calculation.

Cost of Raising Land and Structures.

Estimating the cost of elevating roads and structures required us to obtain estimates of (1) the area ofdeveloped land that would be elevated, (2) the density of structures, and (3) unit cost factors.

The extrapolation equation assumes that the cost for elevating structures could be described as

Costslr = aslr

Shoreline_length + bslr

buildings,

where the number of buildings is area multiplied by housing density.


28/28

Suggested references

green house effect and sea level rise

Documents