Global Warming and Sea Level Rise

Evidence: The long-term record:

- Multi-proxy record from ice cores, tree rings, sub-fossil pollen, corals, and lake, ocean sediments, etc. shows unusual warming

Evidence for Global Warming

-Theoretical (greenhouse effect) -Short-term (instrumental) record -Long-term (geological) record -Changes in ice coverage -Increased extreme meteorological events -Cooling upper atmosphere

Responses to SL Rise: Retreat (managed retreat)

-removal of existing development & possible relocation - avoid or discourage new building in hazard areas - build only non-permanent, movable, elevated, floating may involve land acquisition, transfer of development rights, conservation easements

Evidence: Theoretical (greenhouse effect)

Greenhouse gases absorb and re-emits energy emitted by the earth's surface (long wave infared radiation) Greenhouse Effect is 'mostly natural' Atmosphere CO2 increase recorded at Mauna Loa Observatory Atmosphere CO2 increase recorded in air bubbles trapped in ice cores

Evidence: Changes in ice coverage

Increasing ice loss and rates of ice loss in all portions of the cryosphere. Very few observtions of ice gain. -Glaciers are retreating almost everywhere around the world (including in the Alps, Himalayas, Andes, Rockies, Alaska and Africa) - Both the extent and thickness of Arctic sea ice has decreased over the last few decades. - Shrinking polar ice sheets - The rate of ice loss from Greenland has increased almost five-fold since the mid-1990s

Holocene (last 8000 y) what is the average sea level rise

0.4 mm/year

If all the ice melted how much would the sea level rise?

216 feet

1 m sea-level rise would affect China...

72 million displaced in China and much agricultural land loss

Intergovernmental Panel on Climate Change (IPCC)

A large group of scientists from around the globe asked to answer key questions about climate based on published scientific literature

International Effects

About 10% of population (600 million people) live in flood-prone areas - Agriculture concentrated at low elevations

Inundation

Water covering normally dry land

Longer-Term Coastal Inundation

global sea level rise, relative sea level rise (land subsidence)

Episodic Coastal Inundation Events

storm surge, tsunamis, inland flooding, and shallow coastal flooding Destabilization of the West Antarctic ice sheet could lead to 5 meter increase (17 ft total)

IPCC 2014 Report (AR5) found very likely

that the rate of global mean sea level will increasee due to global warming.

Evidence: The short-term (instrumental) record:

All global temp. reconstructions show warming since 1880 - Most of this warming has occurred since the 1970s - Increase of: 0.8 oC = 2 oF - All 10 of the warmest years occurring in the recent past 12. - Ocean warmth also increasing: ARGO temperature profiling 0-700 m layer

20TH century SL rise due to:

Alpine glacier loss (15%): contributes 0.6 mm/yr to sea level rise . Most glaciers world-wide are in retreat Ice sheet loss (25%), contributes 1 mm/yr to sea level rise . Greenland and Antarctic Ice Sheets are melting at accelerating rates Thermal Expansion (52-65%): water density decreases with heating global 20th century warming ~0.6 C would produce 1.6 mm/yr sea-level rise Regional variation because of uplift (e.g. Canada due to post-glacial rebound) and subsidence (e.g. Gulf Coast) Rates of SL rise in SE and Florida are greater than the global average of 1.7 cm/decade. very likely that the rate of global SL rise during the 21st century will exceed the rate observed during 1971-2010 due to increased ocean warming and loss of glaciers and ice sheets

Global Warming/Climate Change: Evidence for Human Causation

- 'Hockey stick' curves (temp., CO2) - Match of atmosphere CO2 concentration and fossil fuel use - Change in chemistry of atmosphere CO2 in atmosphere since fossil fuel use - Models show change in temperature can only be explained by CO2 increase - Since the 18th century, record of CO2 concentration in atmosphere matches record of fossil fuels burning - Since the 18th century, carbon chemistry (isotopic ratio) of atmosphere CO2 has changed reflecting an progressively older C source (fossil fuels). - Change in temperature can only be explained by CO2 increase - The only quantitative and internally consistent explanation for the recent global warming is the intensified greenhouse effect caused by the increase in CO2 and other greenhouse gases. - 2007 Fourth Assessment Report by the Intergovernmental Panel on Climate Change (IPCC)

SL rise of 30 cm (about 1 ft) would cause retreat of:

- 50-100 feet in New Jersey - 200-400 feet in California -100-1000 feet in east Florida (30-300 m)

Evidence: Increased extreme meteorological events

- Climate change cannot, with certainly, be linked to any single weather event ...only extreme weather trends. - very likely that the number of cold days and nights has ↓ - very likely the number of warm days and nights ↑ - likely that heat wave frequency has ↑ - likely that number of heavy precipitation events over land has ↑ in more regions than it has decreased

Global Warming/Climate Change: Uncertainties

- Climate sensitivity (modeling) - Projections of global air temperature due to thermal inertia i.e. no future CO2 emissions = additonal increase of 0.4 - 0.7 oC by 2035, IPCC, 2013) - Future human emissions - Other drivers of global climate change (feedbacks) - Natural: e.g. volcanic eruptions, solar variation. Human: land-use change, aerosols - Carbon cycle response to warming (feedbacks) - Regional/Local climate responses -Warming likely greatest over land, and in polar region. Generally, wet areas get wetter, dry areas get dryer. - Effects

Volume of the ocean basins -Varies due to long-term changes in:

- Continent arrangement (plate tectonics) - Rates of seafloor spreading (plate tectonics

Ancient Sea Level Determined using:

- Ice volume calculation using ratios of stable isotopes of O and H in ice and sediment cores - location of ancient coral reefs - human (historical) records - buried datable surfaces - modeling Sea level was higher during the Mesozoic Era but has not been much higher than its present level over the past 30 million years

Volume of water in the ocean - Varies due to changes in:

- Land-based ice volume (not sea ice) - Changes in terrestrial water storage - Ocean Temperature (thermal expansion

Evidence: Atmospheric temperature profile

- Satellites measure less heat escaping out to space, in the IR wavelengths that CO2 absorbs

Many scientists argue that the AR5 SL rise estimates are too conservative:

- doesn't include contributions from ice sheet melt since we do not understand ice sheet physics well enough - assumes linear SL increase, but may be accelerating - tipping points! - West Antarctic ice sheet instability and collapse may occur - 2 - 6 m SL increase by end of century is possible

Major challenges in response to sea level rise

- multiple management goals, competing preferences of stakeholders and social conflicts - ever increasing human-population, migration, development - systems are already stressed and resources are limited in developing countries - poor are most vulnerable - involves long-term (>30 y) planning and investment where costs are uncertain and politicians not responsible - quantitative predictions of future coastal change remain difficult

Actual loss due to sea level rise depends upon:

-composition/stability of shoreline, sediment supply, shore slope and geometry, vegetation, storm patterns, humans

Local (relative) sea level is controlled by:

1. Global sea level 2. Vertical movement of land surface Subsidence due to: - plate tectonics - ice or sediment loading - oil or water extraction Uplift due to: - plate tectonics - post glacial rebound - enhanced buoyancy(?) (e.g. Florida platform dissolution) 3. Local ocean surface (currents, winds, atm. pressure)

Global sea level is controlled by:

1.) Volume of water in the ocean 2.) Volume of the ocean basins

Effects of SL Rise

1.)Inundation/flooding 2.)Shoreline erosion 3.)Damage to natural 4.)resources/ecosystem 5.)Storm Impact Magnification 6.)Saltwater intrusion 7.)Damage to man-made infrastructure 8.)Danger to human health

Over the 20th century, average SL rise of

1.7 mm/year and 3.2 mm/year for 1993-2010

1 m sea-level rise would affect Bangladesh...

13 million displaced in Bangladesh, 16% of national rice production lost

Global Warming/Climate Change: Common arguments

Climate is always changing. Earth has been warmer in the past ...such as during the Cretaceous Period. BUT A predicted global temp. rise of 4 oC by 2100 would make it warmer than Earth has seen in the past 40 m.y. Global warming has stopped 16 years ago. BUT This is only for surface atmosphere temps. Ocean still warmed. Always have these periods of stasis. Too short of a time period to be significant.

Florida impacts will be among the greatest in U.S.

Greatest size of at risk population (75% live in a coastal county) Large area of low elevation (8,426 miles of tidal shoreline) high incidence of hurricanes - high $$ value of coastal buildings & infrastructure - reliance on coastal tourism - limestone bedrock: 1. porous aquifer allow saltwater intrusion, 2. Conventional seawalls not effective

What is the IPCC report based on?

IPCC report is not based on what these scientists 'think' or 'believe' but upon the consensus of scientific research

Saltwater intrusion

SL rise accelerate movement of saltwater into freshwater surface and groundwater sources near the coast - occurs much further inland than land loss - drinking and irrigation water wells must be abandoned.

Weather

The state of the atmosphere at a given time and place with respect to temp., cloudiness, moisture, wind, etc.

Damage to natural resources/ecosystem

Tidal wetlands (bogs, salt marshes, swamps, sea grass, mangrove) are important: - high biological productivity and biodiversity - sequester large amounts of carbon - provide habitat, nesting, feeding for juvenile forms of many of organisms such as shorebirds and fish - improve water quality by trapping contaminants - buffer storm impacts and erosion, stabilizes shorelines - provide recreation opportunities

Responses to SL Rise: Accommodation

alter design so structures or infrastructure resist damage or operate more efficiently in new SL regime - Retrofit or alter design of structures or infrastructure by: - raise structures (houses, bridges, etc.) - improve storm water drainage - increase setbacks from watercourses - reduce liability

Damage to man-made coastal infrastructure

coastal industries and infrastructure (transport, power, water supply, sewerage) are highly sensitive SL rise. - rarely built to accommodate SL rise - asset exposure estimated at 9% of global GDP in 2070

Responses to SL Rise: Protection

defensive measures to mitigate (lessen) the impacts of rising seas: 'hard' methods and 'soft' methods: (natural protection)

Danger to human health

expansion of brackish and saline water bodies in coastal areas may increase the incidence of vector-borne diseases, diarrhea and hypertension - degradation fisheries and aquaculture which contribute significantly to the dietary protein of millions of people and world trade

IPCC 2014 Report (AR5) found virtually certain that

global average air and ocean temperatures are rising.

Magnifies the impacts of storms:

higher storm surge, greater flooded area, - deeper waters near shore results in faster flow, higher waves and impacts on shorelines and coastal structures - impairs storm water drainage systems

IPCC 2014 Report (AR5) found it extremely likely

that most of the observed increase in global average temperatures since the mid-20th century is due to the increase in man-made greenhouse gas concentrations.

1 m sea-level rise would affect Egypt...

would affect 6 million people in Egypt and 15% loss of agricultural land