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Global warming may not be the culprit after all when it comes to Artic changes

Climate data can be difficult to analyze. Take for instance global temperature changes. Whereas the Northern Hemisphere has been warming, the Southern half of the planet is cooling. While Antarctic Ice is at near-record levels, the Northern Pole is warming at an unprecedented pace-- much faster than global warming models predict.

A new study published in the journal Nature identified a possible cause for this discrepancy. It identifies a natural, cyclical flow of atmospheric energy around the Arctic Circle. A team of researchers, led by Rune Graversen of Stockholm University, conclude this energy flow may be responsible for the majority of recent Arctic warming.

The study specifically rules out global warming or albedo changes from snow and ice loss as the cause, due to the "vertical structure" of the warming ... the observed warming has been much too weak near the ground, and too high in the stratosphere and upper troposphere.

This study follows hot on the heels of research by NASA, which identified "unusual winds" for rapid Arctic ice retreat. The wind patterns, set up by atmospheric conditions from the Arctic Oscillation, began rapidly pushing ice into the Transpolar Drift Stream, a current which quickly sped the ice into warmer waters.

A second NASA team, using data from the the GRACE (Gravity Recovery and Climate Experiment) satellite, recently concluded that changes in the Arctic Oscillation were "mostly decadal in nature", rather than driven by global warming.



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By Andy35W on 1/8/2008 12:28:10 PM , Rating: 2
As per my last graph

http://www.metoffice.gov.uk/corporate/pressoffice/...

I don't see many downs since the last Little Ice age in the late 1800's. In fact none at all, but again it may be wrong, so please provide contrary evidence.

You make some good points about whether it is man made or not for the last 100 or so years but you cannot say " we all know ..." repeatedly as if it is obvious, you have to show it by some facts and figures or a graph. We don't all know.We are willing to be educated though or see more data to chew over.

And when did localised anecdotal evidence ever illustrate anything about a global statistical process over a long period of time? That's like me claiming global warming because of hurricane Katrina. That sort of thing IS nothing of significance. Trends will always be more relevant.

Finally, Peru was a very bad example to choose. It is just south of the equator but it's highest mountain is at 21000 feet as it lies along the Andes mountain chain. So is that snapshot illustrative of the "cooling" of whole of the southern hemisphere for 2007? No. It shows nothing at all.


By modelmania on 1/8/2008 2:17:08 PM , Rating: 2
quote:
I don't see many downs since the last Little Ice age in the late 1800's. In fact none at all, but again it may be wrong, so please provide contrary evidence.


Here is a recent graph from the National Climatic Data Center:

http://www.ncdc.noaa.gov/img/climate/research/2005...

It shows in broad strokes:

1. Temperature dropping from 1880 to 1893 (.1deg)
2. Going up from 1893 to 1897 (.1deg)
3. Going down from 1897 to 1908 (.2deg)
4. Going up from 1908 to 1942 (.4deg)
5. Going down from 1942 to 1950 (.1deg)
6. Staying the same from 1950 to 1975
7. Going up from 1975 to 1998 (.6deg)
8. Staying the same since 1998

Many ups and downs in the past 130 years.

quote:
You make some good points about whether it is man made or not for the last 100 or so years but you cannot say " we all know ..." repeatedly as if it is obvious


Sorry for assuming that we all know. But I assumed that everyone in this discussion is aware of the Medieval Warm Period. There is an excellent graph I found in a presentation by Robert Carter graphing oxygen isotope data for the last 5000 years. The data is from the GISP2 Greenland ice core. Look at Page 9 of this 14 page PDF file.

http://icecap.us/images/uploads/200705-03AusIMMcor...

The caption reads:
quote:
FIG 10 - Oxygen isotope time series for the last 5000 years, GISP2 Greenland ice core (light line; same dataset as Figure 7), fitted with a
moving average (dark line; after a slide by Andre Illarianov, 2004). The Late 20th Century Warm Period represents the latest of a regular
millennial cycle of similar warm periods (grey stripes). The Late 20th Century Warm Period may have equalled the magnitude of the
Mediaeval Warm Period, but it has not yet attained the warmth of either of the preceding Roman or Minoan Warm Periods.


On that same page, Fig 11 shows the rate of temperature changes (per 100-year interval) over the last 48000 years based on oxygen isotope ratios from the same GISP2 data. It clearly shows much greater rates of change than the most recent 100 years in many (if not most) of the centuries in the last 48000 years. Here is the caption of that graph:
quote:
FIG 11 - Rate of temperature change for the last 48 000 years, in °C/century, based on the analysis of oxygen isotope ratios from the
GISP2 ice core (same dataset as Figure 7; after a slide by Andre Illarianov, 2004). Note that during the last 9000 years of the Holocene,
temperature change occurred regularly at rates between +2.5° and -2.5°C/century. Earlier, during the last glaciation, rates of change
as high as 15°C/century are indicated.


You said:
quote:
And when did localised anecdotal evidence ever illustrate anything about a global statistical process over a long period of time?


I chose the word "illustrate" as opposed to "support" or "corroborate" or "demonstrate". Illustrate does not mean that it supports the conclusion. As I stated the conclusion of cooling temperatures in the Southern Hemisphere is supported by temperature measurement data.

The examples used were illustrative not supportive.


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