evidence: The Little Ice Age is even less well defined than the medieval warm period. Climatologists are generally agreed that, at least for Europe, North America, New Zealand and Greenland, temperatures fell after 1300 to around 1800 or 1850, although with many ups and downs. There was a cold period in the first decade of the fourteenth century, another around 1430 and again in 1560. The end of this period of increasingly harsh temperatures could have been as early as 1700, 1850 or even 1900 for Tasmania. The worst period for most of the world occurred between 1550 and 1700.[178] One reasonable interpretation of the data is that the world has been cooling since around 4500 B.C. with a temporary upswing during the High Middle Ages.