Tweet "For an average model, the scenario spread in sea level rise is only 0.02 m by the middle of the century."
UN IPCC, "Climate Change 2007: Working Group I: The Physical Science Basis," Chapter 10, Executive Summary, Sea Level
"Sea level is projected to rise between the present (1980–1999) and
the end of this century (2090–2099) under the SRES B1 scenario by 0.18
to 0.38 m, B2 by 0.20 to 0.43 m, A1B by 0.21 to 0.48 m, A1T by 0.20 to 0.45 m, A2
by 0.23 to 0.51 m, and A1FI by 0.26 to 0.59 m. These are 5 to 95%
ranges based on the spread of AOGCM results, not including uncertainty
in carbon cycle feedbacks.... In all scenarios, the
average rate of rise during the 21st century very likely exceeds the 1961 to 2003 average rate (1.8 ± 0.5 mm yr–1).
During 2090 to 2099 under A1B, the central estimate of the rate of rise is 3.8 mm yr–1
For an average model, the scenario spread in sea level rise is only
0.02 m by the middle of the century, and by the end of the century it is
Thermal expansion is the largest component,
contributing 70 to 75% of the central estimate in these projections for
all scenarios. Glaciers, ice caps and the Greenland Ice Sheet are also
projected to contribute positively to sea level. General Circulation
Models indicate that the Antarctic Ice Sheet will receive increased
snowfall without experiencing substantial surface melting, thus gaining
mass and contributing negatively to sea level."...
[Ed. note: Translation: No Antarctic melting is predicted, therefore no sea level rise is predicted from Antarctic melt. Antarctic growth is expected to lower sea levels.]
(continuing): "Further accelerations in
ice flow of the kind recently observed in some Greenland outlet glaciers
and West Antarctic ice streams could substantially increase the
contribution from the ice sheets. For example, if ice discharge from
these processes were to scale up in future in proportion to global
average surface temperature change (taken as a measure of global climate
change), it would add 0.1 to 0.2 m to the upper bound of sea level rise
by 2090 to 2099. In this example, during 2090 to 2099 the rate of
scaled-up Antarctic discharge would roughly balance the expected
increased rate of Antarctic accumulation, being under A1B a factor of 5
to 10 greater than in recent years. Understanding of these effects is
too limited to assess their likelihood or to give a best estimate.
level rise during the 21st century is projected to have substantial
geographical variability. The model median spatial standard deviation is
0.08 m under A1B. The patterns from different models are not generally
similar in detail, but have some common features, including smaller than
average sea level rise in the Southern Ocean, larger than average in
the Arctic, and a narrow band of pronounced sea level rise stretching
across the southern Atlantic and Indian Oceans."