California State University Long Beach 

Human induced environmental changes

• Pollution of atmosphere, hydrosphere, and geosphere
• Global warming
• Deforestation
• Loss of ecosystems
• Reduced biodiversity and more.
• None of which occur alone, each change triggers another

Global warming & sea level change

• What warming?
• Northern hemisphere summers are the warmest since at least 1400 A.D.
• Global surface temperatures have increased
• 0.3 to 0.6°C in past 100 years
• 0.2 to 0.3°C in past 40 years
• 1980's were the warmest decade on record (last 140 years of instrumental record)
• Then, the 1990's topped to 1980's by a lot
• After a few cool years from Mt. Pinatubo's eruption, 1995 was the hottest year on record. Then it was sequentially topped by 1996, 1997, and 1998 (the current champion!)
• 2002, 2003, and 2001 are now in 2nd, 3rd, and 4th place behind 1998.

 
• Why would sea level change?
• Thermal expansion of surface ocean water
• Melting or growth of certain glaciers and ice sheets
• Changes in surface and ground water storage

 
• Amount of sea level change
• Approximately 2 cm rise per decade (measured)
• Approximately 20 cm over last 100 years
• Shown by:
• Harbor tide gauges
• Satellite radar altimetry
• But there is no detected acceleration of sea level rise
• As would be expected with increased warming
• 4 to 8 cm in next 30 years (predicted)
• 9 to 88 cm increase in next century from retreat of alpine glaciers and thermal expansion of seawater(predicted)
• 5 to 6 meters potential increase from West Antarctic Ice Sheet (unlikely )
• Presently held back by Ross Ice Shelf, but could "surge."
• West Antarctic ice sheet rests on sea floor
• It is inherently sensitive to warming and sea level rise
• However, models predict that the overall Antarctic ice sheet should actually initially grow with warming, because of increased snowfall
• Complete melting of ice caps would create a 70 meter sea level rise
• Would take 1000s of years, though

 
• Prehistoric (ancient)sea level changes
• Mostly known for periods of major deglaciation (melting ice sheets)
• Up to 1-2 cm per year!
• Not really applicable to modern situation because aren't coming out of a major ice age
• Risks involved with sea level rise
• Over 1/2 of the human population lives within 100 km of the sea
• Over 40 million people are currently subject to storm surge flooding
• Predicted risks with sea level rise
• Drowning of cities and farm lands
• Incursion of salt water
• Increased risk of damage from violent storm (hurricanes)

• Most vulnerable areas:
• Coastal lowlands
• Europe
• London, England
• Venice, Italy
• Netherlands
• Southeast Asia
• Viet Nam
• Thailand
• Bangladesh
• South and Southeastern United States
• Louisiana & Florida
• Island nations
• Micronesia
• Polynesia
• Caribbean
• Indonesia

etc.

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