This narrowing of estimates by the IPCC has caused great concern among alarmists who feared that the IPCC was being "too conservative." Probably as a result of this peer-pressure, estimates have now increased -- as will be seen in the fifth assessment report, due in September 2013. As a reviewer of IPCC reports, I have been able to look at the "second order draft," which was recently leaked to the press. It gives values for 2100 of 45-110 cm (16-40 inches) - about double what IPCC estimated just six years ago in their fourth report. (There is no guarantee that these values will survive in the final printed version.) Still, they are very much smaller than some of the extreme estimates that have been written up in newspapers and magazines -- and always blamed on Global Warming (GW) from carbon dioxide, released in the burning of fossil fuels.
The relevant clue comes from corals and from geological observations: It seems that SL has been rising for the past centuries at about the same rate as seen by tidal gauges in the last 100 years -- about 18 cm per century. In other words, SL was rising even during the colder Little Ice age, from about 1400 to 1850 AD. This provides further support for the hypothesis that the observed global SLR since 1900 is reasonably independent of the observed temperature rise.
The explanation for this riddle had been suspected for some time, based on historic data of SLR derived independently from measurements of coral growth and from isotope determinations of ice volume. But the picture was filled in only more recently through estimates of the rate of melting of the West Antarctic Ice Sheet (WAIS), by tracing its shrinkage during past millennia (through the receding position of its "grounding line," i.e., the line of contact of the ice sheet with the underlying continental land mass.) Note that the WAIS is not floating sea ice; like a mountain glacier, its melting contributes water to the global oceans.
We can therefore describe the broad scenario as follows: The strong temperature increase that followed the Last Glacial Maximum (LGM) of about 18,000 years ago has melted enough ice to raise SL by 120 meters (400 feet). The rate of rise was quite rapid at first and controlled by the melting of the huge ice sheets covering North America and the Eurasian land mass. These disappeared about 8000-5000 years ago; but the WAIS continued to melt, albeit at a much lower rate -- and it is still melting at about the same rate today. Other, smaller WAIS-like ice sheets may have existed in the Antarctic, but have already melted away.
The principal conclusion is that this melting will continue for another 7000 years or so, until the WAIS disappears -- unless another ice age takes over before then. Moreover, there is nothing that we can do to stop this future sea level rise!
As it turns out, though, sand is not forever. Constant erosion from storms and tides and a rising sea level continue to swallow up chunks of beach along Floridas Atlantic coastline. Communities have spent the last few decades replenishing their beaches with dredged-up sand.
But in South Florida Miami-Dade, Broward and Palm Beach Counties concerns over erosion and the quest for sand are particularly urgent for one reason: there is almost no sand left offshore to replenish the beaches.
seems funny...after the last storm Dauphin Island had sand piled along the road two stories high...trucking it back to the beach where it came from...three feet deep.
The Northwest Passage after decades of so-called global warming has a dramatic 60% more Arctic ice this year than at the same time last year. The future dreams of dozens of adventurous sailors are now threatened. A scattering of yachts attempting the legendary Passage are caught by the ice, which has now become blocked at both ends and the transit season may be ending early. Douglas Pohl tells the story:
The Passage has become blocked with 5/10 concentrated drifting sea ice at both the eastern and at the western ends of Canadas Arctic Archipelago. At least 22 yachts and other vessels are in the Arctic at the moment. Some who were less advanced have retreated and others have abandoned their vessels along the way. Still others are caught in the ice in an unfolding, unresolved drama.
The real question is if and when the Canadian Coast Guard(CCG) decides to take early action to help the yachts exit the Arctic before freeze-up... or will they wait until it becomes an emergency rescue operation?
The first blockage area is at Prince Regent Inlet in position 73.7880535N, -89.2529297W which became blocked on 27th August with 5/10 ice concentration with 7/10 ice pushing.
This effectively closes the 2013 Northwest Passage without Canadian Coast Guard icebreaker escorts for transit. The alternative is a very technical and risky southern navigation through Fury & Hecla Strait mostly blocked with sea ice.
Currently there is a commercial cruise ship on a west to east passage which will reach Prince Regent Inlet in another day. It is unknown if there is a CCG icebreaker in the area to provide assistance since government ships do not provide Automatic Identification Service (AIS) to public AIS websites.
