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|a Sea Level Rise |h [electronic resource]. |
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|a Please contact the owning institution for licensing and permissions. It is the user's responsibility to ensure use does not violate any third party rights. |
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|a This Section addresses three questions:
Has global-mean sea level been rising during the last 100
years?
What are the causal factors that could explain a past rise in sea
level?
And what increases in sea level can be expected in the future?
Despite numerous problems associated with estimates of
globally-coherent, secular changes in sea level based on tide
gauge records, we conclude that it is highly likely that sea level
has been rising over the last 100 years. There is no new evidence
that would alter substantially the conclusions of earlier assessments
regarding the rate of change. Our judgement is that:
The average rate of rise over the last 100 years has been 1.0 -
2.0 mm yr t.
There is no firm evidence of accelerations in sea level rise
during this century (although there is some evidence that
sea level rose faster in this century compared to the
previous two centuries).
As to the possible causes and their specific contributions to
past sea level rise, the uncertainties are very large, particularly for
Antarctica. However, in general it appears that the observed rise
can be explained by thermal expansion of the oceans, and by the
increased melting of mountain glaciers and the margin of the
Greenland ice sheet. From present data it is impossible to judge
whether the Antarctic ice sheet as a whole is currently out of
balance and is contributing, either positively or negatively, to
changes in sea level.
Future changes in sea level were estimated for each of the
IPCC forcing scenarios (using the same simple box model as in
Section 6). For each scenario, three projections - best estimate,
high and low - were made corresponding to the estimated range of
uncertainty in each of the potential contributing factors. It is
found that:
For the IPCC Business-as-Usual Scenario at year 2030,
global-mean sea level is 8 - 29 cm higher than today, with
a best-estimate of 18 cm. At the year 2070, the rise is 21 -
71 cm, with a best-estimate of 44 cm.
Most of the contribution is estimated to derive from thermal
expansion of the oceans and the increased melting of
mountain glaciers and small ice caps.
On the decadal time scale, the role of the polar ice sheets is
expected to be minor, but they contribute substantially to
the total uncertainty. Antarctica is expected to contribute
negatively to sea level due to increased snow accumulation
associated with warming. A rapid disintegration of the
West Antarctic Ice Sheet due to global warming is unlikely
within the next century.
For the lower forcing scenarios (B,C and D), the sets of sea
level rise projections are similar, at least until the mid-21 st
century. On average these projections are approximately
one-third lower than those of the Business-as-Usual
Scenario.
Even with substantial decreases in the emissions of the major
greenhouse gases, future increases in temperature and, consequently,
sea level are unavoidable - a sea level rise
"commitment" - due to lags in the climate system.
This present assessment does not foresee a sea level rise of >_ 1
metre during the next century. Nonetheless, the implied rate of
rise for the best-estimate projection corresponding to the IPCC
Business-as-Usual Scenario is about 3-6 times faster than over the
last 100 years. |
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|a Electronic reproduction. |c Florida International University, |d 2015. |f (dpSobek) |n Mode of access: World Wide Web. |n System requirements: Internet connectivity; Web browser software. |
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|a Intergovernmental panel on climate change. |
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|a dpSobek |c Sea Level Rise |
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|u http://dpanther.fiu.edu/dpService/dpPurlService/purl/FI15060924/00001 |y Click here for full text |
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|3 Host material |u https://www.ipcc.ch/ipccreports/far/wg_I/ipcc_far_wg_I_chapter_09.pdf |y Sea Level Rise |
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|a http://dpanther.fiu.edu/sobek/content/FI/15/06/09/24/00001/Warrick_Oerlemans_1990_Sea Level Risethm.jpg |
