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.
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.
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
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 amoving average (dark line; after a slide by Andre Illarianov, 2004). The Late 20th Century Warm Period represents the latest of a regularmillennial cycle of similar warm periods (grey stripes). The Late 20th Century Warm Period may have equalled the magnitude of theMediaeval Warm Period, but it has not yet attained the warmth of either of the preceding Roman or Minoan Warm Periods.
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 theGISP2 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 changeas high as 15°C/century are indicated.
quote: And when did localised anecdotal evidence ever illustrate anything about a global statistical process over a long period of time?