How accurate is this?

[TimMAz6]

Interesting study that just came out on ice cores......how accurate is this method at determining historic temperatures?

http://www.nbi.ku.dk/english/news/news1 ... -the-past/

[canadianplant]

Concidering they are a relatively new branch of study (only got really popular in the last 50 years, but has gone on for a while), its quite accurate. They can do chemical analysis to get the composition of the atmosphere at the time, trapped pollen, water chemestry, small bacterial life and even seeds).

You cant go back into massive expanses of time, but you can go back 10, 20 thousand years easy, and I think they have some cores that go back 100 000 + years into the past. Its like geology where they use the length of layers to determine time. Its a really interesting branch of study which is opening up more doors in terms of figuring out the past climate, which has been warmer, and cooler then it is today.

I think some people have a hard time understanding this, because many seen to think the climate is static, and hasnt really changed to much in the lifes history. Most studies show that climate change was the driving force in human evolution, as well has been the cause/after affect of all the earths major, and most of the minor extinctions.

We were warmer in the medieval period, and cooler during the time of the plague. There was a volcanic eruption in iceland which dropped the temps in europe in the 1700s. They have found evidence of supervolcanic eruptions in ice core/sediment cores as well. You can also figure out the position of the magnetic north and south pole with ice/sediment cores (thats how we know about magnetic pole shifts).

OF course, it isnt PERFECT, but compared to most science and experiements, this is more accurate than most.

[lucky1]

Interesting article, Tim, and your response, Jesse.
I love this stuff...

Noteworthy too is: "then Antarctica must be responsible for a significant portion of the 4-8 meter rise in sea levels"

Barb

[TimMAz6]

I don't understand how they map the year when the ice melted?

"The top shows a graph of ice sheet surface temperature and altitude. At the beginning of the Eemian, 128,000 years ago, the ice sheet in northwest Greenland was 200 meters higher than today, but during the warm Eemian period the ice mass regressed, so 122,000 years before now the surface had sunk to a level of 130 meters below the current level. During the rest of the Eemian the ice sheet remained stable at the same level with an ice thickness of 2,400 meters."

How do they understand the 200 meter ice melt?

[canadianplant]

Im not an expert, but I would guess that the layers would be thinner or thicker depending on the amount of ice, as well as absence of ice where there should be layers.

[TimMAz6]

200 meters melted..........that's a lot of missing ice and how do you know 100 meters melted then 50 meters 'grew back' then 150 meters melted again..........if 200 meters melted it's gone and there is no evidence of what happened....?

[canadianplant]

heres a good run through of it:

http://earthobservatory.nasa.gov/Featur ... _IceCores/

[TimMAz6]

what causes the temperature to drop or rise? From year 130,000 to 120,000 the temp went from rock bottom to super warm. It happened again in 30,000 to 20,000? Cool stuff. I still don't understand how they understand melting..........it the ice sheet drops 200 meters........a lot of years are lost due to melt??

[canadianplant]

There are lots of things that could cause it to warm relatively fast, including c02 output from volcanoes. Also, the earth tilt shifts, which can give some short term (relatively) warming or cooling.

IIR the more recent change in climate happened when india smashed into asia, which is thought to have played a bit part into the demise of the dinosaurs. The next mot recent I can think of (geologically), would be when south america smashed into central america (few million years ago). All of those changed the worlds climate for the long run. CLimate change happens drastically and more often then people give it credit too. Heinrich events tale 500 years to start, and less then 100 to finish. Thats a geological blink of an eye!

In order to figure out exactly what caused the ice to melt in greenland, they have to date that section of core, then use a bit of detective skills to look in the geolocical/fossil record to see if there was anything going on in the world that would cause that much heating. Usually in ice cores they can get the atmospheric composition due to air bubbles in the ice. IF there was a high amount of co2, they can start to look for volcano activity at that time.