If one has had (say) a sponge with a weight on one end and one removes the weight the previously unweighted end does not fall – in fact it will also rise slightly as the compressive stresses will have been distributed through out the sponge. However if one has a rigid steel plate on top of the sponge and the weight is removed then the previously unweighted end of the plate could fall as it could have been effectively unsupported by the deformed sponge (which would also have been acting as the fulcrum) when the other end was in the weighted condition. Is the latter the correct analogy?

Apologies if the above is geologically simplistic/uninformed – please point me to a reference. I have read the Wikipedia on this but the reference for the UK points to an insurance risk report which doesn’t give a reference for the claim. Thanks

Immediately following the collapse of the Fennoscandian ice-sheet at the end of the ice-age, initial crustal rebound rates reached about 7.5 cm/yr. In the event of Greenland or Antarctica losing their ice, we can expect these rates of land-rise to be seen possibly for several decades. This in itself will displace a considerable amount of water, causing further sea-level rise.

It appears that if you want to establish the maximum extent of some variable over time, the approved method is to have a correct sampling interval. The sampling interval should be frequent enough to ensure that one is not missing the peaks. It is not correct simply to take a series of infrequent measurements over a long period, and draw a smooth line through them, and conclude that one has captured all the highs and lows.

This, comment 8 by Hunter, and approved by TCO, is the sin committed by Morner. Because of this, we cannot rely on a graph produced by Morner which shows there has been minimal recent sea rise, and no acceleration. It must be possible he has missed the peaks and the fluctuations.

The question for the class is: how many samples are there in the Vostok CO2 series? And how long was the period? And how were they linked? And why exactly do we think we know that CO2 is higher now than it has been for many hundreds of thousands of years?

The class will have to use Google to find the CO2 data from Vostok in tabular form, then try plotting it for themselves in a spreadsheet. This should be educational in itself. After they get through with this, they will then revisit the above comments, and some of them at least will have a Zen moment and become enlightened.

Well, that’s what a sense of irony does for you.

the periodic nature of the tide distance between low and high tide seems to be increasing

Tides are very tricky and depend quite sensitively on local underwater topography. The tidal range in Boston Harbor is 9.5 feet. The range on Nantucket Island, 50 miles way, is only about 3 feet. A change in tidal range could easily be due to the dredging.

The data was obtained from locations throughout the globe, although the number of tidal gauges increased and their locations changed over the 130-year period.

These records show that the sea level has risen, and suggest that the rate of rise is increasing.

Over the entire period from 1870 the average rate of rise was 1.44mm per year.

Over the 20th Century it averaged 1.7mm per year; while the figure for the period since 1950 is 1.75mm per year

Looking at he website mentioned in #26 shows that there are large variation in the rate of rise in sea level at various locations, most probably due to subsidence variations. Hawaii has low sealevel rise (rising land?) while Galveston has high sealevel rise (sinking land?). In any case, a major problem for the study has to be that the scientists did not use the same places throughout the 130 years. You can get almost any result you want by selecting the places (im)properly.

From the BBC summary, simple math suggests the average rise found during the 1870-1900 period was .57mm per year, while the first half of the 20th century is 1.65mm per year and the second half of the 20th century, as stated, is 1.75 mm per year. The 1870-2000 figure is surprisingly low, and suggests (unless there was a jump-shift) the early part of the first half of the 20th century probably had low figures too, holding down the 1900-1950 average. This would be enough to produce the “growth” claimed in the 20th centuy. It will be good to see the data sources.

The site referenced in #26 has some long term graphs, and analysis of individual locations. My eyeball does not see a general trend toward growth in the rate of rise in the second half of the 20th century for most places, although perhaps for some. As the graph on the top of this topic shows, current rates of sea rise are very small compared to past rates over the last several thousand years. These past rates were not significantly affected by fossil fuel consumption. The Amsterdam data quoted in the post #11 reference shows about a 1mm per year rise 1870-1925, which is not far from the what you get when you take an average of the 1870-2000 and the 1900-1950 data mentioned in the BBC article. It looks to me right now like the acceleration, if real, was in the early part of the 20th century, not the recent part. For those keeping score (baseball reference) greenhouse gas emissions were much lower in the early part of the twentieth century.

At the current rate of sea level rise and earth subsidence, the rise within the next 100 years will be about 17-20 cms. The Dutch data show 17cm over the last 100 years for the 6 locations shown. According to the Dutch analysis, the IPCC best estimate of sea level rise over the next 100 years has come down with each iteration, from 66 in the first to 48 in the third (TAR). The BBC quotes the Church et al paper as predicting much less than 48 (but more than 17-20). The third IPCC report has a range of 9 to 88 cms. sea level rise for the next 100 yeaars which means it is probably going to be right (or at least in the range), as it claims the sea rise might decrease by half or go up several times. Absent a repeat of the little ice age (possible of course) this range is wide enough to capture pertty much the entire range of results expected. It is a little like predicting that the Americans will elect a Republican or a Democrat for President in 2008.

My household energy use is 24 kwh per day and the lot area is 700 sq. meters. Thus on average 1.4 watts/sq m is being emitted. This is like have 24 100 watt light bulbs running 24/7.

Check your calculations. 24kWh = 1kW * 24h. So, more like 10 x 100W light bulbs running continuously by my reckoning.