Most common type of evidence
Global temperature rise
Sea level rise
Shrinking ice sheets
Declining Arctic ice
Extreme Weather Events
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
Levitus, et al, "Global ocean heat content 1955–2008 in light of recently revealed instrumentation problems," Geophys. Res. Lett. 36, L07608 (2009).
Impact on Coral
Mass coral mortality
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
over the past decade
at some sites in the
believe that at least
one-third of the
world’s coral reefs
are now beyond
Why is climate change a threat to coral
Rising sea temperatures due to
Bleaching - Warmer sea
temperatures can lead to
coral bleaching. When
temeperatures are just a
degree or two warmer than
usual for a few weeks, corals
(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
Why is ocean acidification a threat to coral
As CO2 concentration in
the atmosphere rises, more
CO2 dissolves in the ocean,
making carbonic acid,
making the ocean slightly
This change in water
chemistry can impede the
formation of the coral’s
carbonate skeleton by
reducing the organism’s use
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.
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/
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
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.”
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 rise
Controversy 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
Some scientists dispute the
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.
Over the next few weeks
For prep you will be examining the evidence for
whether climate change is causing or likely to cause
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?