However, NASA's GISS led by James Hansen offers us a more impressive figure extracted from the weather stations (land) and sea surface temperatures (ocean) - a methodology that normally leads to the fastest warming trend. According to
Update: The recent cooling according to HadCRUT3 seems even more unprecedented.If we were fans of the alarm and extrapolated the latter trend, we would deal with 75 °C of global cooling per century. That could indeed be a catastrophe. ;-) If we extrapolated the 0.28 °C month-on-month cooling since December, the cooling would remove 336 °C per century, dropping below 0 Kelvins before 2100. :-) Entertainingly enough, January 2008 was also 0.27 °C (anomaly-wise) colder than June 1988 when Hansen gave his infamous testimony before the U.S. Congress, predicting a dangerous warming in the following 20 years.
No, I am not comparing apples and oranges here. January 2008 was also 0.39 °C colder than January 1988. Incidentally, NCDC shows January 2008 as the global lands' coldest January since January 1982.
Figure 1: Thames, London during the Dalton minimum (in 1814). Click to zoom in.
La Nina (now referred to as a "strong one") might be insufficient to explain the recent cool weather. An unusually quiet beginning of the solar cycle 24 might be another culprit. I won't really endorse the predictions of a new ice age but I find it obvious that the solar activity matters; see also sunspots and climate.
Joseph D'Aleo (a big shot meteorologist, pic) argues that the temperature is strongly correlated with the ENSO index (El Nino vs La Nina) but it lags by 2 months or so. With this assumption, we should expect the global cooling to continue in the following months. Also, he argues that the Pacific Decadal Oscillation (PDO) that switched to the cold phase during this winter (the Great Pacific Climate Shift II?) shouldn't be included separately: its effect is to increase the proportion of El Ninos (warm PDO phase) or La Ninas (cool PDO phase).
Minnesotans: keep on dreaming about global warming (song).