- Home | About
- • Personal Energy Stories •
- My Solar PV System
- The Refrigerator Story
- Lighting Choices
- Lessons from an Energy Meter
- Opt Out of Mail / Phonebooks / etc
- • Essays & Articles •
- Global Warming in a Nutshell
- Power and Energy in a Nutshell
- Why Move Beyond Fossil Fuels?
- • Local Programs •
- EnergySmart - Boulder County
- Longs Peak Energy Conservation
- Borrow an Energy Meter
- • Useful Links •
- TopTenUSA.org / Enervee.com
- DSIREusa.org
| 4. Sea Level Change |
| Satellite Sea Level Data 1993-2010 | Tide Gauge Sea Level Data 1870-2009 |
|---|---|
 |
 |
| The sea level increases when new water is added to the oceans from the melting of ice on land, and sea level decreases when evaporated water from the oceans is retained on land by the growth of glaciers and ice sheets (as during a glacial period). Sea level is also affected by the temperature of the water through "thermal expansion", where warmer water takes up more volume than cooler water, so the oceans expand in response to an increase in temperature. A warmer atmosphere from global warming leads to a warmer ocean after a time lag for the heat transfer and mixing to occur. Since 1993 the "global mean sea level" (GMSL) has been measured accurately by three satellites: TOPEX/Poseidon (launched August 1992), Jason-1 (launched December 2001), and Jason-2 (launched June 2008). This figure shows the amount that sea level has changed since 1993, where zero is the average sea level over the time period. Sea level has increased by almost 60 mm (6 cm, or 2.4 inches) since 1993, at a relatively constant rate of 3.2 mm/year, which is over 50% faster than the average rate of sea level increase over the 20th century (see next figure).
Figure prepared from published data by the Sea Level group at CSIRO (the Australian national scientific research organization). |
This record of the global mean sea level (GMSL) back to 1870 was derived from tide gauge measurements by CSIRO (dark blue line). The light blue region is the range of uncertainty in GMSL from the tide gauge measurements. The tide gauge data are consistent with the satellite GMSL measurements (red) in the region of overlap since 1993. Sea level has increased by about 240 mm (24 cm, or 9.4 inches) over this time period, and the rate of sea level increase (slope) has increased in recent decades compared to earlier in the 20th century.
Figure prepared from published data by the Sea Level group at CSIRO (the Australian national scientific research organization). |