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AndrewW
join:2009-03-07
Toronto, ON
kudos:1
1 edit | reply to lugnut
Re: [Weather] Arctic sea ice melts to record low said by lugnut :http://www.cbc.ca/news/canada/story/2012/09/20/arctic-sea-ice-melt.html?cmp=rss
quote:
“The thaw this year broke all the records that we had previous to this and it didn’t just break them, it smashed them," Barber told CBC News.
“The Arctic is changing so rapidly right now and that is connected to our global climate system, so it’s really a precursor to what is coming for the rest of the planet and it really should be an eye-opener for people.”
Scientists say that at this rate there could be an ice-free Arctic as early as the summer of 2015.
I guess milder, shorter winters and longer, hotter summers are going to be the norm in Canada from now on... While the Arctic ice cover is shrinking, the Antarctic ice cover is actually increasing.
Furthermore, if we restrict the discussion to the Holocene period, proxy evidence suggests that the warmest period in the Arctic occurred between 10,000 and 6,000 years ago, peaking about 7,500 years ago (known as the HTM or Holocene Thermal Maximum) with an average temperature about 2 to 4 degrees warmer then today. The Arctic was largely seasonally ice free during this period and the polar bears survived. The climate has largely been cooling since then with relatively brief warmer periods. Note that these paleo-climate studies are site and methodology biased producing slightly different numbers but they generally agree with the above theme. So a mostly summer ice free Arctic is not unprecedented territory nor are we in uncharted waters as some have claimed. | |
 Wolfie00My dog is an elitistPremium
join:2005-03-12
kudos:5 | said by AndrewW:While the Arctic ice cover is shrinking, the Antarctic ice cover is actually increasing.
Absolutely false. The claim that Antarctic ice is increasing is based on observations of sea ice, not the all-important ice sheets. Sea ice is mostly seasonal and has shown some growth because of factors like increased precipitation and freshwater from melting of the ice sheets, and stratospheric cooling in part from ozone losses. The loss of Antarctic ice sheet surface mass balance has actually been accelerating at the rate of more than 14.5 Gt/yr**2 and is now losing on the order of as much as 300 Gt/year in some years. Greenland and the Antarctic together, in fact, are major contributors to sea level rise because of the ice loss.
There are dozens of papers on the subject... this is one:
»ps.uci.edu/scholar/velicogna/fil···2011.pdf
Your comment on the Holocene Maximum is irrelevant as it was not associated with any of the factors happening today. It disproportionately affected the Arctic probably due to a phase of Milankovitch cycles, and globally was cooler than today overall. Nor were the temperature gradients anywhere even remotely like what we are experiencing today -- the total temperature excursion during the entire HTM was less than the warming we've caused in just last 100 years.
I never claimed that an ice-free Arctic summer was unprecedented. I said that the current CO2 levels were totally unprecedented -- certainly during the entire period of regular 100Ky glaciation, and probably in some 15 million years. Nothing like this has happened since the dawn of humanity. This is indeed uncharted territory.
--
"Everyone is entitled to their own opinion, but not their own facts."
― Daniel Patrick Moynihan | |
AndrewW
join:2009-03-07
Toronto, ON
kudos:1 | Wow, I say Antarctic ice cover is actually increasing and you say Antarctic sea ice “has shown some growth” yet my statement is totally false.
As for my comment on the Holocene, I think it is totally relevant as I was responding not to you but to the OP and his take on the CBC story that Arctic ice was at a record low and I was showing otherwise.
Your assertion that “globally was cooler than today overall” is unproven, despite what some models and Milankovitch cycle theory adherents claim.
As for temperature excursions some sites in Siberia show average temperatures about 4 degrees higher then today during the HTM and one site in Greenland a temperature increase of 7 degrees in 50 years.
As for CO2 levels they may be unprecedented for humans but not for the planet nor its ecosystem. Your earlier claim that we had an “alien ecosystem” 15 million years ago is sheer rubbish. Many species living and flourishing today predate that period. | |
Wolfie00My dog is an elitistPremium
join:2005-03-12
kudos:5
1 edit | Wow, indeed.  Apparently you don't understand the difference between seasonal sea ice and the vast continental ice sheets that are the dominant form of Antarctic ice. The evidence of accelerating Antarctic ice melt is in the graph right in front of you. Instead of continuing to misrepresent the facts, read the paper I linked. There are many others.
Maybe some basic factual exposition would be conducive to a better understanding of the subject matter here.
Fact #1: Antarctic sea ice is unimportant either as a bellweather of climate change (or of sea level rise, obviously), because the sea ice is almost entirely seasonal -- it forms in the winter and floats off northward and pretty much all melts every summer. The Antarctic is a continent surrounded by ocean where the sea ice is extremely mobile. This is the exact opposite of the Arctic which is largely ocean surrounded by land.
The important indicator of Antarctic trends is the massive continental ice sheets which are losing mass at a huge and accelerating rate. The Antarctic is also more insulated from overall planetary warming and less sensitive to climate change but that's beside the point. The Antarctic overall is losing ice mass, period. And losing it fast, at rates that are quite well quantified. Any other claim reflects either lack of knowledge or intentional deception.
Fact #2: Whether the HTM was warmer than today or not is an irrelevant red herring. If you take the average of eight major 12Ky reconstructions, it wasn't, but if you pick one you like better, you can show otherwise, with no greater or less credibility. It's ultimately completely irrelevant because the causes were completely unrelated to anything going on today and mainly based on orbitally-induced insolation changes. It also mainly affected high latitudes and had a much different distribution than contemporary warming being driven by GHG's. Some info on that here. In fact bringing up the HTM at all is just about as pointless as bringing up the Medieval Warm Period, another denialist favourite.
When articles like the one in the OP talk about Arctic devastation from global warming being "unprecedented", I think the term could be fairly interpreted to mean "unprecedented in recorded history", and that something that happened 10,000 years ago for entirely different reasons doesn't change the validity of the statement.
Fact #3: Local and regional climate is not global climate. The fact that high-latitude insolation caused some point in Siberia to be 4 deg. warmer than today during the HTM (other Arctic areas were even warmer) or that some isolated site had a rapid temperature increase says nothing at all about the global climate. The importance of the fact that the present temperature increase is both extremely rapid and globally synchronous cannot be understated. That, and its relation to the unprecedented increases in post-industrial atmospheric CO2 is what this is all about.
Fact #4: The risks posed by anthropogenic global warming are entirely related to the stresses imposed by the extremely rapid rate of change, and little to do with long-term equilibrium points. First there are ecosystem stresses. Everything living today is adapted to its local climate, and the destabilization of ecosystem balances and adaptations can have catastrophic results and even lead to ecosystem tipping points. Second there are physical climate system stresses. Rapid changes in atmosphere and ocean circulation systems lead to weather extremes, powerful storms, long-term changes to regional climate, and general destabilization. And there, too, there is strong evidence that the earth's climate systems operate in terms of tipping points that create sudden and severe changes to large geographic areas.
--
"Everyone is entitled to their own opinion, but not their own facts."
― Daniel Patrick Moynihan | |
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