Spring and fall, in polar terms, are more aptly morning and evening twilight. Particularly in the continental interior, the temperature drops quickly when the Sun sets in March, and rises with the Sun's rise in September. The data were collected by unattended automatic weather stations and transmitted by satellite every two minutes to the University of Wisconsin in Madison, from where they were sent by request over the Internet to a winterer at McMurdo Station, who produced this graph as part of an evaluation of latitudinal temperature variations. At the South Pole, the nights are six months long, extending from sunset on March 21 to sunrise on September 21. Offshore cyclones occur with little warning.
Winds typically reach hurricane strength within an hour and persist for several days.
The stretch of ocean between Antarctica and the tip of South America is considered the most hostile in the world and has claimed numerous ships over the centuries. Ice core records provide evidence that atmospheric greenhouse gases such as carbon dioxide and methane have increased markedly during the past 200 years and are presently more prevalent than at any time in the past 160,000 years. These records also show that low temperatures of the ice age occurred when greenhouse-gas concentrations were low. Meteorological observations have been recorded only in recent decades, and then only in scattered localities, so long-term temperature trends remain uncertain. The glacial systems that occur in the Peninsular region are the most delicate in Antarctica and the most vulnerable to climatic warming.