Sea Level

Sea levels are rising

Graph: Sea Level Change since 1993 (NASA: Climate: Indicators)
  • The blue line shows how the sea level has risen between 1993 and 2014. 
  • This rise has continued.
  • See the latest NASA Sea Level graph.
  • Sea level has risen an average of 3.16 millimeters a year.
  • A rise of 3.16 mm per year may not sound like much – but the ocean covers about 70 percent of Earth’s surface.  A 3.16 mm rise is an enormous amount of water.
  • The sea level drop in 2011 was due to the 2010 / 2011 floods in Australia. Extreme rains dumped vast amounts of water onto Australia. The drop was temporary as this water evaporated or flowed back to the sea.

Sea levels are rising faster

  • The sea level rose 1.7 mm a year between 1870 and 2000
  • The sea level was rising at 3.2 mm a year in 2018
  • The rate of sea level rise has almost doubled.

Sea level rise is the yardstick for global warming (NASA).

The graph shows a clear upward trend, so this “yardstick” shows a clear warming trend.

(Sea Level Rise: Global Warming’s Yardstick: NASA)

Sea levels are rising due to ice melting

Some of the heat build up is melting ice in places like Antarctica and Greenland, the meltwater runs into the ocean and this increases sea levels.

Sea levels are rising due to ocean warming

  • Water expands as it warms, like mercury in a thermometer.
  • In a mercury thermometer, when the mercury warms, the mercury expands, moves up the calibrated thermometer scale, and we can read the temperature on the scale.
Mercury Thermometer
  • As the ocean warms, the ocean water expands, increasing sea levels and forming a sort of thermometer. Satellites are monitoring this thermometer.

Our oceans are absorbing the heat

  • The oceans are absorbing over 90% of the current build-up of heat in our planet, due to greenhouse gases in our atmosphere.
  • The atmosphere and the ground absorb only about 5% of this heat accumulation.

Air temperatures are an unstable measure of global warming

The “average global temperature” records have been the basis for suggestions that global warming paused after 1998. When you look at the movement of sea levels, there is clear evidence of continued warming.

Air temperatures are important for humans as we live in this air.  However, air temperature is an unstable measure of global warming. This is because the oceans have a far greater capacity to retain heat than the atmosphere.

Air temperature is like the tail on a dog. Just because the tail is moving, it does not mean the dog is moving. During an El Nino period, movement of heat from the oceans into the atmosphere significantly increases global air temperatures.

Dangers

Rising sea levels already a problem

  • Rising sea levels already cause problems in low-lying coastal areas of the world.
  • The Intergovernmental Panel on Climate Change (IPCC) predicts that sea levels will rise a total of 0.18 to 0.6 meters (7 inches to 2 feet) between 1990 and 2100.

Potential climate refugees: Bangladesh

  • The population of Bangladesh is 157 million
  • About half of them live less than 5 meters (16.5 feet) above sea level.
  • In 1995, the sea half-submerged Bangladesh’s Bhola Island leaving 500,000 people homeless.
  • Scientists predict Bangladesh will lose 17 percent of its land by 2050 due to flooding caused by climate change.
  • The loss of land could lead to as many as 20 million climate refugees from Bangladesh.”
  • Climate change could greatly increase the number of refugees heading for places like Australia.
  • Inaction on climate is kick-starting the boats, boatloads of climate refugees.

(National Geographic Society: Encyclopaedia:  Climate Refugees)
(now a broken link) http://education.nationalgeographic.com.au/education/encyclopedia/climate-refugee/?ar_a=1

Climate change risks to Australian coast

By 2100, rising sea levels may threaten up to 247,000 residential buildings in Australia. The cost of replacing them would be $63 billion, valued at 2008 prices.

Ultimate sea level rise could be 66 metres

If we destabilise the ice in Greenland and Antarctica, sea level could ultimately rise by 66 metre.

Sea levels are steadily increasing. This is dangerous as they have the potential to rise by tens of metres and cause widespread devastation.

One Reply to “Sea Level”

  1. Steve Manders May 18, 2015 at 10:24 am

    Australia’s Cocos (Keeling) Islands (CKI) in the Indian Ocean, some 2,750 km north west of Perth, are arguably one of the nation’s regions most threatened by climate change and sea level rise. CKI is a ring of coral islands most of which are less than 5 m above sea level. Two islands are inhabited – Home Island by around 450 people predominantly of Cocos Malay background and West Island by around 150 predominantly European background.

    The Australian government commissioned a major investigation into potential impacts of climate change and sea level rise in 2009, available at:
    http://www.ga.gov.au/webtemp/image_cache/GA21023.pdf

    Reply

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