Most common type of evidenceGlobal temperature rise

Sea level riseOcean Warming

Shrinking ice sheetsDeclining Arctic iceRetreating Glaciers

Extreme Weather EventsOcean Acidification

According to NASA

“The oceans have absorbed much of this increased heat, with the top 700 meters (about 2,300 feet) of ocean showing warming of 0.302 degrees Fahrenheit since 1969.”

http://climate.nasa.gov/evidence/Levitus, et al, "Global ocean heat content 1955–2008 in light of recently revealed instrumentation problems," Geophys. Res. Lett. 36, L07608 (2009).

http://www.scientificamerican.com/article/how-will-warmer-oceans-affect-sea-life/

Impact on CoralMass coral

mortality over the past decade at some sites in the Seychelles.

Researchers from Warwick university believe that at least one-third of the world’s coral reefs are now beyond recovery.

http://www.ipcc.ch/publications_and_data/ar4/wg2/en/contents.htmlhttp://www2.warwick.ac.uk/newsandevents/news/effects_of_climatehttp://environmentalresearchweb.org/cws/article/research/32885/

Global map of the overall impact that 17 different human activities are having on marine ecosystems. Insets show three of the most heavily impacted areas in the world (left), and one of the least impacted areas (right).

Why is climate change a threat to coral reefs?

Rising sea temperatures due to global warming Bleaching - Warmer sea

temperatures can lead to coral bleaching. When summertime water temeperatures are just a degree or two warmer than usual for a few weeks, corals expel zooxanthellae (organisisms that live on coral and provide their coral host with food and oxygen) and ultimately the corals can die.

The severity of marine diseases could increase with temperature.

http://www.eoearth.org/article/Coral_reefs_and_climate_change

Why is ocean acidification a threat to coral reefs? As CO2 concentration in

the atmosphere rises, more CO2 dissolves in the ocean, making carbonic acid, making the ocean slightly more acidic

This change in water chemistry can impede the formation of the coral’s carbonate skeleton by reducing the organism’s use of calcium.

http://www.eoearth.org/image/Oceanchemfig.jpg

According to NASA

“The carbon dioxide content of the Earth’s oceans has been increasing since 1750, and is currently increasing about 2 billion tons per year. This has increased ocean acidity by about 30 percent.” In effect lowering by on average 0.1 units.

http://climate.nasa.gov/evidence/C. L. Sabine et.al., “The Oceanic Sink for Anthropogenic CO2,” Science vol. 305 (16 July 2004), 367-371; Copenhagen Diagnosis, p. 36. Also see: http://www.pmel.noaa.gov/co2/OA/

Coral reef bleaching

Freshwater from floods

Pollution

Disease

Sediment

Cyanide fishing

But many local problems can cause bleaching:

http://www.nytimes.com/2010/09/21/science/earth/21coral.html?_r=0

What does the future hold?The most conservative IPCC climate change

scenarios, ocean pH will decrease by 0.1 to 0.3 units.

The 4th IPCC assessment predicted an increase of 1-4 ˚C in ocean temperature during this century.

Sea-level rise is expected to exacerbate inundation, storm surge, erosion and other coastal hazards, thus threatening vital infrastructure, settlements and facilities that support the livelihood of island communities.

http://www.eoearth.org/article/Coral_reefs_and_climate_change

http://www.ipcc.ch/publications_and_data/ar4/wg2/en/contents.html

According to NASA…

“Global sea level rose about 17 centimeters (6.7 inches) in the last century. The rate in the last decade, however, is nearly double that of the last century.”

http://climate.nasa.gov/evidence/Church, J. A. and N.J. White (2006), A 20th century acceleration in global sea level rise, Geophysical Research Letters, 33, L01602, doi:10.1029/2005GL024826.

Evidence of sea level riseControversy over exact rise in sea levels and causes – other factors

such as isostatic rebound need to be considered.However, it is frequently used as evidence of climate change.

In their 4th Report the IPCC predicted a sea level rise of 0.18 – 0.38m by 2100 in the most optimistic scenario and 0.26 – 0.59m in the most pessimistic.

http://www.bbc.co.uk/climate/impact/sea_level.shtml

http://climate.nasa.gov/keyIndicators/index.cfm#SeaLevel

Some scientists dispute the data…The Swedish geologist and physicist Nils-Axel Mörner,

formerly chairman of the INQUA International Commission on Sea Level Change, claims "the sea is not rising," and “it hasn't risen in 50 years." So If there is any rise this century it will "not be more than 10cm (four inches), with an uncertainty of plus or minus 10cm".

Mörner claims that on six visits to the Maldives he could find no evidence of any change, and even claims that the sea level has dropped in Tuvalu.

He also claims that there were factual errors in sea level data, due to faulty tide gauges – NASA and others claim these errors have been rectified.

http://www.telegraph.co.uk/comment/columnists/christopherbooker/5067351/Rise-of-sea-levels-is-the-greatest-lie-ever-told.html

Over the next few weeksFor prep you will be examining the evidence for

whether climate change is causing or likely to cause extreme weather.

Next week we are going to consider the winners and losers associated with climate change.

Watch the video and consider whether some areas of the world are likely to suffer more than others – is there anything that can be done?