How accurate is historical weather data?

When we look at record highs in history we tend to look at a baseline point centred on 1880. So, when we see headlines speaking of new records, how accurate can these be?

While it is true that modern meteorology is still relatively young in the grand scheme of things, many of the instruments used today have a long history. Thermometers for example were developed by ancient Greeks before being widely adopted in the 17th century.

It wasn’t until the 1600s that the standardised thermometer of today came along.

The main issue with historic records is that many have been lost or were handwritten. Meaning there is no global, digitised record of weather readily available. That is not to say that it does not exist, ship logs hold records of conditions encountered on their travels but remain inaccessible.

It just so happens that of all the accurate data we have available today, the earliest reliable starting point is in the year 1880.

From here we also have insights from ocean sediment, tree rings, ice cores, and coral which can unveil ancient climates and events, helping build the picture of our planet going back thousands of years.

Meteorologists and volunteers are working around the world to digitise old weather data, eventually, we will likely see the benchmark of 1880 fall to an earlier date.