Overview of Climate Changes and Illustrative Impacts - Climate Stabilization Targets - page 37

Glaciers and small ice caps are losing mass and contributing to sea
level rise. Glaciers and small ice caps are estimated to have contributed
0.8±0.17 mm y -1 SLR for the 1993-2003 time period, but they are not in
balance with the present climate. The total sea level equivalent of glaciers
and ice caps is 0.7 m. On average, glaciers and ice caps need to decrease in
volume by about 26% to attain equilibrium with current warming, resulting
in a minimum contribution to total change in sea level of about 0.18±0.03
m. For the AR4 A1B warming scenario, a contribution of 0.37±0.02 m SLR
from glaciers by 2100 is projected. {4.8}
20th and 21st Century Changes in Sea Level
Global sea level has risen by about 0.2 m since 1870. The sea level
rise by 2100 can be expected to total at least 0.60±0.11 m from thermal
expansion (0.23±0.09 m) and loss of glaciers and ice caps (0.37±0.02 m).
This lower limit is higher than previous studies due especially to improved
information about glaciers. Additional contributions from Greenland and
Antarctica are expected. Assuming ice loss from Greenland at the current
rate, the total global sea level rise would be 0.65±0.12 m by 2100. As-
suming a doubling in ice discharge from both Greenland and Antarctica,
the total global average sea level rise would be 0.88±0.12 m by 2100. We
therefore estimate a range of total global sea level rise in 2100 of about
0.5 to 1.0 m. Global sea level rise is a consequence of global warming and
is caused by ocean water expansion and loss of ice stored on land (glaciers,
small ice caps, and ice sheets). Satellite measurements show sea-level is
rising at 3.1±0.4 mm y -1 since these records began in 1993 through 2003.
This rate has decreased somewhat in the most recent years (2003-2008) to
2.5±0.4 mm y -1 due to a reduction of ocean thermal expansion from 1.6±0.3
mm y -1 to 0.37±0.1 mm y -1 , whereas contributions from glaciers, small ice
caps, and ice sheets increased from 1.2±0.4 mm y -1 to 2.05±0.35 mm y -1 .
Oceans respond slowly to global warming. The planet is already committed
to a further 0.05 m sea level rise through thermal expansion alone over the
next several centuries as a response to the past warming. Thermal expansion
alone is expected to contribute about 0.23±0.09 m to sea level rise for the
A1B scenario by 2100. Some semi-empirical models predict sea level rise
up to 1.6 m by 2100 for a warming scenario of 3.1°C, a possible upper limit
that cannot be excluded. {4.8}