The more observations we have, the more certainty we have about the conditions at the time," she said.
The weather records, some dating back to the mid-1800s, were normally meticulously kept in logbooks, with entries made several times a day recording information such as temperature, barometric pressure and wind direction, as well as comments about cloud cover, snow drifts or rainfall.
However, most of this "incredibly valuable" information had never been transcribed, and had not previously been used by scientists for modelling.
"We have 150,000 images of logbook pages from archives in the UK and Scandinavia that need to be keyed. Each image has about six days of data, which can include up to 70 pieces of information. That adds up to millions of observations to key over the course of the project," Ms Pearce said.
Anyone with an internet connection could log on to the Southern Weather Discovery website (www.southernweatherdiscovery.org) and immediately begin keying-in data, doing as much or as little as they liked. Niwa was hoping to have 250,000 completed observations by the middle of next year, and would be extremely grateful for any help.
The weather data would be fed into global daily weather reconstructions going back to the 1800s, to give better daily weather animations and a longer-term perspective of events that occurred in the past.
"It will also help us understand how the weather generated from Antarctica and the Southern Ocean impacts on New Zealand," she said.