Northern and southern hemisphere climates follow the beat of different drummers

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Over the last 1000 years, temperature differences between the Northern and Southern Hemispheres were larger than previously thought. Using new data from the Southern Hemisphere, researchers have shown that climate model simulations overestimate the links between the climate variations across the Earth with implications for regional predictions.

Over the last 1000 years, temperature differences between the Northern and Southern Hemispheres were larger than previously thought. Using new data from the Southern Hemisphere, researchers have shown that climate model simulations overestimate the links between the climate variations across Earth with implications for regional predictions.

These findings are demonstrated in a new international study coordinated by Raphael Neukom from the Oeschger Centre of the University of Bern and the Swiss Federal Research Institute WSL and are published today in the journal Nature Climate Change.

The Southern Hemisphere is a challenging place for climate scientists. Its vast oceans, Antarctic ice, and deserts make it particularly difficult to collect information about present climate and, even more so, about past climate. However, multi-centennial reconstructions of past climate from so-called proxy archives such as tree-rings, lake sediments, corals, and ice-cores are required to understand the mechanisms of the climate system. Until now, these long-term estimates were almost entirely based on data from the Northern Hemisphere.

Written By: Science Daily
continue to source article at sciencedaily.com

6 COMMENTS

  1. @OP – The Southern Hemisphere is a challenging place for climate scientists. Its vast oceans, Antarctic ice, and deserts make it particularly difficult to collect information about present climate and, even more so, about past climate.

    There are significant local effects because of the differences at the poles. The land-mass with its ice cap at the South Pole surrounded by the uninterrupted circulation of the Southern Ocean, produces quite different weather patterns from the Arctic Ocean surrounded by land-masses.

    However, multi-centennial reconstructions of past climate from so-called proxy archives such as tree-rings, lake sediments, corals, and ice-cores are required to understand the mechanisms of the climate system. Until now, these long-term estimates were almost entirely based on data from the Northern Hemisphere.

    Over long time-scales, there are bound to be great seasonal differences between the hemispheres, because of the Milankovitch PRECESSION PERIODICITY cycle of 23,000 years. (See linked diagrams.), resulting from the interaction of the eccentricity of the Earth’s orbit and the axial tilt.

  2. @OP – However, multi-centennial reconstructions of past climate from so-called proxy archives such as tree-rings, lake sediments, corals, and ice-cores are required to understand the mechanisms of the climate system. Until now, these long-term estimates **were almost entirely based on data from the Northern Hemisphere. **

    Really???

    Climate and atmospheric history of the past 420,000 years from the Vostok ice core, Antarctica – http://www.nature.com/nature/journal/v399/n6735/abs/399429a0.html

    • Not sure of the relevance of your point Alan. The Vostock ice core is just one of many cores pulled in both the Antarctic and Arctic over many years. As an aside the Vostock core suffers from significant bacterial and lead contamination.

      The point the article makes is that one cannot solely rely on proxy data from the Northern hemisphere to make equally strong assumptions about events in the Southern hemisphere. There are statistically significant differences between the two hemispheres requiring a potential reexamination and modification of the models based on the data as new data from the Southern hemisphere becomes available. A very reasonable scientific approach. jcw

      In reply to #2 by Alan4discussion:

      @OP – However, multi-centennial reconstructions of past climate from so-called proxy archives such as tree-rings, lake sediments, corals, and ice-cores are required to understand the mechanisms of the climate system. Until now, these long-term estimates were almost entirely based on data from the No…

      • In reply to #3 by kaiserkriss:

        @OP – However, multi-centennial reconstructions of past climate from so-called proxy archives such as tree-rings, lake sediments, corals, and ice-cores are required to understand the mechanisms of the climate system. Until now, these long-term estimates were almost entirely based on data from the Northern Hemisphere.

        Not sure of the relevance of your point Alan. The Vostock ice core is just one of many cores pulled in both the Antarctic and Arctic over many years.

        My point is that coral terraces show climate changes reflected in GLOBAL sea-levels, not just one hemisphere, so their global position is largely irrelevant – while the comparison of the Vostok and Greenland ice cores, allows comparison of the two hemispheres.

        As an aside the Vostock core suffers from significant bacterial and lead contamination.

        Do you have details of this? Lead and other chemical “contamination”, is usually a record of volcanism or atmospheric industrial pollution.

        The point the article makes is that one cannot solely rely on proxy data from the Northern hemisphere to make equally strong assumptions about events in the Southern hemisphere.

        I agree, and indeed explained the key differences @ 1. These are very basic, and it would be amazing if climate specialists were not aware of them!

        There are statistically significant differences between the two hemispheres requiring a potential reexamination and modification of the models based on the data as new data from the Southern hemisphere becomes available. A very reasonable scientific approach.

        That may well be the case, but it does not justify the erroneous claim that current data on corals and ice cores is “almost entirely based on data from the Northern Hemisphere.”

        • Must have missed the point about Coral reefs reflecting changes in sea level, abd I agree they do. reflect sea level changes.

          I had remembered a reference to contamination being made, but couldn’t find it again except in this wiki entry
          http://en.wikipedia.org/wiki/Ice_core under the core contamination heading. jcw

          In reply to #4 by Alan4discussion:

          In reply to #3 by kaiserkriss:

          @OP – However, multi-centennial reconstructions of past climate from so-called proxy archives such as tree-rings, lake sediments, corals, and ice-cores are required to understand the mechanisms of the climate system. Until now, these long-term estimates were almost en…

          • In reply to #5 by kaiserkriss:

            I had remembered a reference to contamination being made, but couldn’t find it again except in this wiki entry http://en.wikipedia.org/wiki/Ice-core under the core contamination heading. jcw

            Core contamination

            Some contamination has been detected in ice cores. The levels of lead on the outside of ice cores is much higher than on the inside.[12] In ice from the Vostok core (Antarctica), the outer portion of the cores have up to 3 and 2 orders of magnitude higher bacterial density and dissolved organic carbon than the inner portion of the cores, respectively, as a result of drilling and handling.

            Thanks for that. – Presumably if this is a known problem any competent researchers will have taken this into account and have taken their samples from the inner portion. I would suspect that smearing of outside layers and contamination from drilling, would be a potential problem for any core sample.

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