Posted by Henry Bauer on 2015/01/15
Human-caused global warming, and even more terrifyingly human-caused climate change, is blamed for all sorts of things: more frequent and more extreme tornados and hurricanes and tsunamis, proliferation of viruses, shortage of fresh water, and of course rising sea levels that will submerge coastal cities. For example (from Reuters via Sydney Morning Herald):
“Sea level rise in the past two decades has accelerated faster than previously thought in a sign of climate change threatening coasts from Florida to Bangladesh, a study said on Wednesday. . . .
IPCC scenarios . . . range from a sea level rise of 28 to 98 cm this century . . . .
the rise has accelerated, with the most recent rates being the highest on record . . . .
Sea level rise is gnawing away at shores from Miami to Shanghai”.
All this is based on a letter, just published on-line by Nature, that used some mathematical techniques to re-evaluate, from admittedly incomplete data, what the sea-level rise actually was from 1901-1990; concluding that it was a bit less than formerly thought, at about 1.2 mm per year rather than 1.5 mm; and leapt to 3 mm per years in the last two decades. A terrifying acceleration!
Human activities apparently threaten us with between 28 cm (11 inches) and 98 cm (39 inches) in this century. That wide range of expectation should make obvious how uncertain these projections are; but what is altogether missing is an assessment of how this expectation compares with what one might expect from purely natural causes.
During the last Ice Age, which ended about 15,000 years ago, sea level was 400 feet lower than now. Quite naturally, sea level must rise as things warm up after the Ice Age and glaciers melt. But how rapidly?
On average, from purely natural causes, sea level has risen in the past, following an Ice Age, by about 5 inches per century. However, the rate varied tremendously during different eras; for example, pulses of as much as 100 inches per century for 5 centuries (Vivien Gornitz, “Sea level rise, after the ice melted and today”).
In other words, purely natural causes have in the past produced rates of sea-level rise considerably greater than the merchants of doom and gloom are now projecting as being caused by human actions, projecting on the basis of computer models that failed to predict the present decade-and-a-half lull in “global warming”.