Australian sea levels have been falling for 7000 years

It’s hard to measure sea levels, because land often moves up and down too (which is known as “isostatic“). But Australia is stable tectonically, so the Australian sea-level record is more useful than most. It preserves the holocene era and the rises and falls, and correspond more with glacio-eustatic (ice equivalent) sea-level changes, rather than changes in land masses.

During the coldest days of the last ice age (known as a glacial maximum) 20,000 years ago, the oceans were 125m lower than today. They peaked at around 1 -2 meters higher than present between 9000 and 5000 years ago, and have been trending down ever since. Our current rate of 30cm/century (if that continues) hardly seems unprecedented or highly unusual. And 10% of that is apparently due to an isostatic “adjustment”. Worse, if you look at the raw data, the rate is closer to zero. Hmm. Lucky we have all those adjustments eh?

If Australian sea levels keep falling at this rate, we might really need to save That Reef.

Clearly there are many details yet to be worked out about sea-levels.

That phenomenal rise out of the ice age:

…

 

WA and NSW coastlines are considered the […]

October 15th, 2012 | Tags: , , | Category: Global Warming | Print This Post Print This Post | |

The Warmest Year Antidotes

What do you say when the Big PR bell is rung? You know the litany: “2010 was the warmest since measuring began, and the previous decade was also the warmest decade on record.” (eg The AGE)

Sure, and the world has been warming for 300 years, long before the industrial revolution. The trend hasn’t changed as our emissions rose. No one knows exactly why it started rising back then, but it wasn’t CO2. Sure and 150 years of “records” is not long. It was warmer 1000 years ago, 2000 years ago, 5000 years ago and 130,000 years ago. In fact its been warmer for most of the last 10,000 years than it is today, and it’s been warmer for most of the last 500 million years. Only people who think CO2 matters keep repeating that it’s warmed from 1850 to now without pointing out the bigger perspective. Sure, and the records have been set with thermometers like this one (next to concrete and exhaust vents — see below). There probably weren’t too many car parks or air conditioners in 1880 either. Not to mention the non-random adjustments, and that mystery about how 75% of thermometers are ignored.

Nothing about the […]

January 14th, 2011 | Tags: , , | Category: Global Warming | Print This Post Print This Post | |

The big picture: 65 million years of temperature swings

Greenland Interglacial Temperatures – last 10,000 years. Are we headed for an ice age? (See below for more detail.)

David Lappi is a geologist from Alaska who has sent in a set of beautiful graphs–including an especially prosaic one of the last 10,000 years in Greenland–that he put together himself (and which I’ve copied here at the top).

If you wonder where today’s temperature fits in with the grand scheme of time on Earth since the dinosaurs were wiped out, here’s the history. We start with the whole 65 million years, then zoom in, and zoom in again to the last 12,000 from both ends of the world. What’s obvious is that in terms of homo sapiens history, things are warm now (because we’re not in an ice age). But, in terms of homo sapiens civilization, things are cooler than usual, and appear to be cooling.

Then again, since T-rex & Co. vanished, it’s been one long slide down the thermometer, and our current “record heatwave” is far cooler than normal. The dinosaurs would have scoffed at us: “What? You think this is warm?”

With so much volatility in the graphs, anyone could play “pick a trend” and depending […]

February 18th, 2010 | Tags: , , , , , , , , , | Category: Cryosphere, Geology, Global Warming, Holocene, Paleolithic | Print This Post Print This Post | |
 
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