​Reanalyses are educated estimates of how the atmosphere behaved in the recent past. They are built by combining computer models of the atmosphere and ocean with weather observations to build an approximation of what the entire atmosphere was doing every six hours or so.
 
Climatologists and meteorologists all over the world use reanalyses to research our climate and weather. Most of the reanalysis products that exist cover the entire planet, but if you want to study storms over Paris for example, or wind changes in the Spanish Pyrenees, then it’s better to use a regional reanalysis, which has a higher spatial resolution.

Recovering historical weather observations for long-term climate analysis is a well-established practice in many places in Europe, where written documents cover several centuries. In Australia, written records only begin with British settlement in the late 18th century, as the indigenous Aboriginal people maintain their history through largely oral traditions.

However, this does not mean that there is no historical climate information for the Great Southern Land. Recent efforts are uncovering a treasure trove of historical weather and climate data that are shedding light on both the regional and global climate. Here are just a few examples: