The first part of the fourth assessment report of the IPCC, the UN’s panel on climate change, was published in February. This report (known internally as AR4-WG1, Assessment Report 4 – Working Group 1) warned that sea levels could rise by 20-60 cm this century, and as much as seven meters in the very long term. This is the result of deglaciation and rising water temperatures (warm water taking up more space than cold). This prediction soon met criticism from glacier experts and other climate researchers who actually work out on the melting ice. The rise in levels will be much faster and much worse, according to them.
Even though I’m no expert, I was able to clearly see the speed of the deglaciation on Greenland last summer. The world’s largest glacier, the Jacobshavn Glacier, has doubled its deglaciation speed over the past ten years. In Disco Bay, the sea where the glacier dumps as much ice and fresh water as the entire city of New York uses in a year, the water temperature rose from 3°C to 7°C between 2002 and 2007.
A few weeks ago, the IPCC was forced to re-evaluate its cautious stance on the rise in sea levels, and published an updated climate change report (called the Synthesis Report of the IPCC Fourth Assessment Report, released 17 November). With respect to the earlier conclusions on Greenland and the polar regions, they write that the rise of sea levels in the two areas “may be larger than projected.” The reason for this revision was new observations from Greenland and the Arctic: in the words of the report, “This is because dynamical processes seen in recent observations but not fully included in ice-sheet models assessed in AR4 could increase the rate of ice loss”” (i.e., the report released earlier in the year; see p.20).
Translated from the IPCC’s academic prose, this means quite simply,”We were wrong in February. In all likelihood deglaciation in Greenland and elsewhere will lead to much greater increases in sea level than we ever dreamed of. And these major rises can occur within this century, as opposed to what we predicted in February.”
How much, then, can sea levels rise as a result of deglaciation and the ever warmer water? In the earlier report, AR4-WG1, they spoke of a range of 20-60 cm.
Old IPCC-report, maximum sea rise until 2100; 0,59 cm.
In the revised report from November, on the other hand, they are clearer. There they write, “… causing an eventual sea level rise much larger than projected for the 21st century. The eventual contributions from Greenland ice sheet loss could be several metres…” (emphasis added; see p.21 of the Synthesis Report). So, in the later report, they speak of rising sea levels of several meters. As early as 2015 the level can have risen by 1.4 meters. If that were to happen, you could write off a large part of the world’s communities in coastal areas. Millions of people would become climate change refugees.
Revised IPCC report, sea rise could be much bigger.
The IPCC’s revised estimates are extremely worrisome. If they were altogether too cautious in their initial judgement of deglaciation in Greenland, one can wonder: Is the same true in other areas? Is the IPCC intentionally cautious in order to protect their academic integrity; to avoid being accused of crying “Wolf” once too often? But if they issue a warning too late, well, then it may just be too late!