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Arctic sea ice heads for record low
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therefore we can't claim that such ice melts didn't occur during say the similar warming of the early 20th century.
Satellite records are nice to have but not the only way of measuring Arctic sea ice. There are good records starting at about 1950 and less reliable sources going much further back
http://nsidc.org/cryosphere/sotc/sea_ice.html
http://www.skepticalscience.com/Arctic-sea-ice-hockey-stick-melt-unprecedented-in-last-1450-years.html
http://earthobservatory.nasa.gov/Features/wardhunt/
[...]In the summer of 2002, graduate student Derek Mueller made an unwelcome discovery: the biggest ice shelf in the Arctic was breaking apart. The bad news didn’t stop there. Lying along the northern coast of Ellesmere Island in northern Canada, the Ward Hunt Ice Shelf had dammed an epishelf lake, a body of freshwater that floats on denser ocean water. This epishelf lake, located in Disraeli Fiord, was host to a rare ecosystem, and it was the largest and best-understood epishelf lake in the Northern Hemisphere. When the Ward Hunt Ice Shelf fractured, the epishelf lake suddenly drained out of Disraeli Fiord, spilling more than 3 billion cubic meters of fresh water into the Arctic Ocean.When the Ward Hunt Ice Shelf originally formed, it blocked the mouth of Disraeli Fiord, cutting it off from the Arctic Ocean. In the process, the ice shelf trapped driftwood inside the epishelf lake and kept other pieces of driftwood from entering. Pieces of driftwood found along the shores of Disraeli Fiord have been there since the ice shelf formed, and by radiocarbon dating the wood, researchers have been able to estimate the minimum age of the ice shelf. “There simply are no radiocarbon dates more recent than 3,000 years before present,” said Jeffries. This ice shelf, in existence for at least three millennia, has now encountered conditions it can no longer survive.
Note the last link - the ice shelf survived 3 thousand years and started collapsing in the early 2000s. Every metric for the Arctic is now much lower than it was even then.
What's happening in the Arctic right now is completely unprecedented going back thousands of years and "just natural cycles" really does not cut it as an explanation.
If you want to try and find a way to go on believing nothing is happening I'm sure you can. Real world measurement is complex and messy, you can always find room to dismiss it and claim "Well we don't really know, maybe it's just an error of some type".0 -
Yes, that's the theory, but my point is that the perception has been generated that this is already happening when in fact there is no proof that it is. We have had some recent northern blocking in the past few years - especially this summer - and I would claim that that has contributed to the increased melting season this year, but these satellite data we are going on are only one climate period (3 decades) old, therefore we can't claim that such ice melts didn't occur during say the similar warming of the early 20th century.
We can claim it though. We have very good data of the periphery of the ice pack going well back to the 19th century. We have a lot of aerial and submarine observations from much the 20th century, with shipping logs further back, the ships couldn't get past the edge of the pack so we can't say much about the interior though!
We do know the ice did drop back during the warming up to 1940/50 but what we're seeing now is very different.
Some ice shelves, such as Ward Hunt, have had driftwood thousands of years old (carbon dating) trapped in the ice yet have only recently begun to break up and detach.
There are several reconstructions of sea ice in the Arctic over the last 10,000 years or so. The last time the ice may have been this low could have been during the Holocene Climatic Optimum, around 8,000 years ago.
One of the most recent reconstructions is from Kinnard et al., here's the graph from it
And a link to the papers abstract here
Which includes the line
"both the duration and magnitude of the current decline in sea ice seem to be unprecedented for the past 1,450 years"
EDIT: Sharper is too quick for me!0 -
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Well, actually, no.
First, you haven't actually addressed my point regarding statistics and outliers; you're throwing up irrelevant points about more measurements, and more people being affected. Those are true, but they don't affect the nature of the statistics: there are more outlying events, even in well-known, long established datasets. I'm also not talking at all about the effects of events; I'm talking about the measurements of weather on a day to day basis.
For some context, read this:
http://www.guardian.co.uk/world/2011/jun/13/extreme-weather-flooding-droughts-fires
... which gives an overview of the situation.
This: http://www.bbc.co.uk/news/uk-18653274
... talks about the record-breaking rain in the UK earlier this year, as an example.
... and finally, if you're taking the sceptical route, try the fact that insurance companies, who deal only in cold hard numbers, are adjusting their premiums to handle weather:
http://www.thejournal.ie/home-insurance-costs-to-rise-on-weather-worries-218810-Sep2011/
They're not doing that for fun, or because they heard it from someone down the pub.
It may be so claimed. I'm not claiming that. I'm claiming that there are more outlier events than would normally be expected.
I'm not talking about those either. Indeed, I'm specifically talking about the longer established, older datasets, like British Isles weather records. The fact that there are more measurements out there - and I agree that, for example, we're aware of tropical storms that nobody would have known about thirty years ago. But that's not the kind of dataset I'm talking about.
And I said nothing about effects of weather. Do try to address what's going on here, not what some nebulous public is saying, old bean.
Firstly, let's forget this insurance premium idea. Insurance premia reflect the exposure to claims. Much of the increase in claims has been the result of the poor demographic planning I mentioned. Take Ireland as one example. The increase in claims through flooding can't really be put down to staggeringly high rainfall episodes, as the data will show, but is to do with the increase exposure of policy holders to flooding through poor planning (eg. building in natural flood plains), decreased run off from increased concretisation (is that a word?), damming issues, etc. That is one example where weather events that have occured not just in recent decades but during the previous century or more are having more of an effect nowadays. Another example we see bandied about in relation to AGW is Boscastle. Another is Katrina. And most recently Isaac. So the cost of insurance is a non-runner when it comes to this discussion.
Regarding the CET. Of course many of the warmest years have occured in recent decades, no one can deny that. But I find it interesting that these warm years seem to have come about through anomalously warmer summer and autumn months, but the warmest winter months still date back to pre-1960s (December 1974 = December 1934). For some reason the warm records are not being seen in winter. I don't know why that is as you would expect all seasons to show a rising trend, especially as, if you exclude the past two winters, the winters of the past few decades have been classed as "mild" (as in ask a snow-lover). April 2011 upset the applecart a little bit and led to the warm Spring.
Sea ice has no doubt undergone a sharp decline in recent years, no one doubts that either. I am not denying that warming is happening, but I do dispute the extent of our influence on it. My point in this thread has been that when a flood does occur (as in a town gets flooded despite just a modest rainfall event), it is put down to AGW and not to the other factors that caused it.0 -
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Am I missing something? This graph shows this year not as bad as 2007.
http://www.natice.noaa.gov/products/ice_extent_graphs/arctic_weekly_ice_extent.html
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Am I missing something? This graph shows this year not as bad as 2007.
I could be wrong, but I think thats a graph for extent rather than area.What is the difference between sea ice area and extent?
Area and extent are different measures and give scientists slightly different information. Some organizations, including Cryosphere Today, report ice area; NSIDC primarily reports ice extent. Extent is always a larger number than area, and there are pros and cons associated with each method.
A simplified way to think of extent versus area is to imagine a slice of swiss cheese. Extent would be a measure of the edges of the slice of cheese and all of the space inside it. Area would be the measure of where there is cheese only, not including the holes. That is why if you compare extent and area in the same time period, extent is always bigger. A more precise explanation of extent versus area gets more complicated.
http://nsidc.org/data/seaice_index/0 -
maquiladora wrote: »I could be wrong, but I think thats a graph for extent rather than area.
http://nsidc.org/data/seaice_index/
Yeah but why the difference between the extent I posted above and this extent?
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