While parts of Australia have been experiencing a warmer than average autumn, Europe and parts of North America have experienced extreme cold weather caused by a strong Arctic Oscillation, similar to the weather in 2010.
According to Peter Hannam in the Brisbane Times, the temperatures in Sydney has reached 20 degrees C for 26 consecutive days, a new record for this late in May in more than 150 years of record keeping. It is also likely to be one of the driest 30 days in autumn on record for Sydney. Offshore along most of the NSW coast, sea surface temperatures are between 1.5 and 3 degrees above normal.
Globally, March 2013 was tied with 2006 for 9th warmest March on record, since records started in 1880. The northern Hemisphere averaged 0.78 degrees C. above normal, placing it tied for 11th warmest on record. It was also the 10th warmest on record for the southern Hemisphere, averaging 0.52 degrees C. above the 1951-1980 average. The global temperature for March 2013 averaged 0.59 degrees C. above the 1951-1980 average.
In the article below republished from the Conversation under Creative Commons licence, Blair Trewin, Australian Bureau of Meteorology and Karl Braganza, Australian Bureau of Meteorology explain what is happening with cold extremes and why average temperatures over the hemisphere and the global average are still increasing.
