© USGSFear-mongering regarding Arctic sea ice is the most acute of all that brought forward by global warming doomsayers.

I hope to be around in 2020, when some have suggested those of us on the sceptics' side should have been vindicated, but I think we will prevail much sooner. The Arctic heat-wave of 1920-1940 is of course well-known to real Arctic climate scientists. I reviewed 32 temperature data sets for Arctic stations to 2004 some with very long records. In 2006 I could find only one with higher temperatures in 2004 than in the late 1930s or early 1940s - that was on the eastern coast of Greenland. Since then I have reviewed dozens of papers on surface air temperature, sea surface temperatures, ice-mass, glacier speeds and sea-ice, and all show a clear cyclic pattern of roughly 70 years. Some Greenland and Alaskan temperatures peaked in 2006-2008, but the pattern looks set to repeat.

The latest Arctic heat wave is not identical to the last - firstly it is higher, by maybe 20% in some places, and secondly, the hot-spots are different. But one thing is clear - it is driven by two distinctive factors - a 14% increase in clouds over the North Pole and Beaufort Sea between 1980-2000, and the incursion of warm Atlantic water under the ice and into the Beaufort Gyre. The rapid summer ice loss is due to melting from above (infra red from the clouds) and below (warm Atlantic water).

The strength of the Beaufort Gyre determines how far Atlantic water penetrates the Arctic - when the Pacific Decadal Oscillation is warm and Alaskan Shelf winds are low, the gyre weakens and may reverse flow; when cold (as it has been since late 2006), the Alaskan interior cools, the winds strengthen and the gyre strengthens accordingly - there is a lag of a few years.

Thus, this domino effect from the Pacific will eventually reach the area between Greenland and Norway and summer sea-ice ought to return to the long-term norm (unless there really is a strong greenhouse element - which I can't see it greater than the difference between this warm period and the last - ie about 20%) and unless there is an even steeper decline in global temperatures due to the quiet sun effect.

On the latter - there is a body of evidence that during quiet solar periods, the jetstream is shifted along with Arctic pressure systems that lead to blocking high pressure over Iceland - sending the jetstream further south and cooling western Europe. The eastern seaboard of the USA gets a little warmer, but the mid-West suffers late springs, dry summers, and bitter winters - not good for the breadbasket of the world!

We should get to see this play out over the next five years.