Observations vs Projections
Recent observations show the observed sea levels from tide gauges (blue)
and satellites (red) are tracking near the upper bound (black line) of the IPCC 2001
projections (grey shading and black lines) since the start of the projections in 1990 (Rahmstorf
et al. 2007). This upper limit leads to a global-averaged sea-level rise by 2100 of 88 cm
compared to 1990 values. These observations do not necessarily indicate that sea level will
continue to track this upper limit - it may diverge above or below this upper limit.
However, the ice sheet uncertainties referred to above are essentially one-sided –
i.e. they could lead to a significantly larger sea-level rise than current projections but
are unlikely to lead to a significantly smaller rise. Note also that greenhouse gas emissions
are now tracking just above the highest of the SRES emission scenarios used in calculating
these projections (GCP_CarbonBudget 2007,
Raupach et al. 2007; Canadell et al. 2007).
Canadell, J.G., C. Le Quéréc, M.R. Raupach, C.B. Field, E.T. Buitenhuis, P. Ciais,
T.J. Conway, N.P. Gillett, R.A. Houghton and G. Marland (2007), Contributions to accelerating
atmospheric CO2 growth from economic activity, carbon intensity, and efficiency of
natural sinks. PNAS, 104, 18866-18870, doi: 10.1073/pnas.0702737104.
Rahmstorf, S., A. Cazenave, J.A. Church, J.E. Hansen, R.F. Keeling, D.E. Parker and
R.C.J. Somerville (2007), Recent Climate Observations Compared to Projections.
Science, 316, 709, doi:10.1126/science.1136843.
Raupach, M.R., G. Marland, P. Ciais, C. Le Quéré, J.G. Canadell, G. Klepper and C.B.
Field (2007), Global and regional drivers of accelerating CO2 emissions.
PNAS, 104, 10288-10293, doi:10.1073/pnas.0700609104.