Those moving goalposts again
Warmists are good at moving the goalposts. Catastrophe (runaway warming) was once slated to strike once atmospheric CO2 levels reached 400 ppm. We are now there with NO change in the temperature. So do they say "Sorry. We were wrong"? No way. They are just more vague about when warming will strike. And there were LOTS of bad things that were supposed to happen by 2014 which have not happened. Still no sign of penitence. They just don't name dates much anymore.
So rather a lot of laughs in the report below. The authors claim to have shown that sea levels suddenly started rising 150 years ago. So is that evidence of man-made global warming? It certainly runs counter to the usual Warmist claim that manmade global warming got going only in the second half of the 20th century. So the finding must contradict Warmism, right? It must show that sea-level was rising long before the industrial upsurge of the postwar era?
Not on your Nelly! We read below that 150 years ago was "the same time humanity began to pump greenhouse gases into the atmosphere by burning fossil fuels". The onset of manmade global warming has suddenly been shunted back by around 100 years! VERY mobile goalposts!
And a small niggle. In the journal abstract also reproduced below the number of readings they took is given as ~1,000. Note the tilde (~), meaning "approximately". Don't they know how many records they used? Amazingly sloppy data processing if so.
But the whole enterprise is a nonsense. Present-day readings of sea level are difficult enough without thinking you can do it accurately 6,000 years back. See here where it shows that the sea level rise since 1970 has been 4.7 inches in Boston and 8.02 inches in Atlantic city. The rise in Atlantic city has been double what it was in Boston! So which is the true sea level? The obvious answer is that there is no such thing. So what these authors measured was just one sampling of sea levels which may tell us nothing about any general sea-level over the last 6,000 years
Melting glacial ice and ice sheets have driven seas to levels unmatched in the past 6,000 years, says a study out this week in the Proceedings of the National Academy of Sciences.
Researchers studied examples of past sediments in Australia and Asia that dated back 35,000 years and found that overall, the planet's sea level was fairly stable for most of the past 6,000 years.
Things began to go haywire about 150 years ago, the same time humanity began to pump greenhouse gases into the atmosphere by burning fossil fuels.
"There's something going on today that wasn't going on before," said Kurt Lambeck of the Australian National University, who was lead author of the study, in an interview with the Australia Broadcasting Corp. He said the sea level rise is affected by increasing temperatures.
As the Earth's temperature warms, so do the seas. Heat-trapping greenhouse gases cause more land ice (glaciers and ice sheets) to melt and water to expand.
Lambeck told the Guardian that the sea level increase of the past 100 years is "beyond dispute."
Sea level has risen nearly 8 inches worldwide since 1880, but it doesn't rise at the same level. In the past century or so, it has climbed about a foot or more in some U.S. cities such as Charleston, Norfolk and Galveston because of the added influence of ocean currents and land subsidence.
Global sea level will rise 1 to 3 feet around the world by the end of this century, according to this year's Fifth Assessment Report by the United Nations' Intergovernmental Panel on Climate Change.
Sea level and global ice volumes from the Last Glacial Maximum to the Holocene
By Kurt Lambeck et al.
Several areas of earth science require knowledge of the fluctuations in sea level and ice volume through glacial cycles. These include understanding past ice sheets and providing boundary conditions for paleoclimate models, calibrating marine-sediment isotopic records, and providing the background signal for evaluating anthropogenic contributions to sea level. From ~1,000 observations of sea level, allowing for isostatic and tectonic contributions, we have quantified the rise and fall in global ocean and ice volumes for the past 35,000 years. Of particular note is that during the ~6,000 y up to the start of the recent rise ~100−150 y ago, there is no evidence for global oscillations in sea level on time scales exceeding ~200 y duration or 15−20 cm amplitude.
The major cause of sea-level change during ice ages is the exchange of water between ice and ocean and the planet’s dynamic response to the changing surface load. Inversion of ~1,000 observations for the past 35,000 y from localities far from former ice margins has provided new constraints on the fluctuation of ice volume in this interval. Key results are: (i) a rapid final fall in global sea level of ~40 m in <2,000 y at the onset of the glacial maximum ~30,000 y before present (30 ka BP); (ii) a slow fall to −134 m from 29 to 21 ka BP with a maximum grounded ice volume of ~52 × 106 km3 greater than today; (iii) after an initial short duration rapid rise and a short interval of near-constant sea level, the main phase of deglaciation occurred from ~16.5 ka BP to ~8.2 ka BP at an average rate of rise of 12 m⋅ka−1 punctuated by periods of greater, particularly at 14.5–14.0 ka BP at ≥40 mm⋅y−1 (MWP-1A), and lesser, from 12.5 to 11.5 ka BP (Younger Dryas), rates; (iv) no evidence for a global MWP-1B event at ~11.3 ka BP; and (v) a progressive decrease in the rate of rise from 8.2 ka to ~2.5 ka BP, after which ocean volumes remained nearly constant until the renewed sea-level rise at 100–150 y ago, with no evidence of oscillations exceeding ~15–20 cm in time intervals around 200 y from 6 to 0.15 ka BP.