Research links changes in day length to climate prediction

Scientists have made a key breakthrough in the quest to accurately predict fluctuations in the Earth’s rotation and thus the length of the day, potentially opening up new predictions of the effects of climate change.

A team of scientists led by Professor Adam Scaife of the University of Exeter has used the latest mathematical modeling to show how day length fluctuations can be predicted more than a year in advance – much longer than is currently possible.

The team suggests that long-term forecasts also come from a new atmospheric source for long-term predictability of weather and climate change.

Importantly, the research shows a definitive link between geodesy – or the precise measurement and understanding of the Earth’s shape, size, orientation and gravity – and climate prediction.

The study is published Natural science.

Professor Scaife, a climate expert from the University of Exeter’s Department of Mathematics, says that “although changes in day length are small, they are important for applications that require very precise time measurements such as GPS”.

Momentum has long been known to play a fundamental role in the structure and variability of the Earth’s atmosphere.

As the Earth spins on its axis, its combined mass and spin result in what appears to be a steady spin. However, changes in surface winds and changes in high and low pressure can change this, and when the atmosphere speeds up due to increased winds, the Earth’s rotation slows down accordingly, causing the length of the day to increase.

However, until now, the long-range predictability of these day length fluctuations was unknown.

A new study shows that fluctuations in the atmosphere momentum moment and that the length of the day is predictable more than a year in advance and that atmospheric changes have an important effect on regional weather and climate.

Using a series of predictions from a dynamic climate model, scientists were able to predict signals in the atmosphere that propagate slowly and coherently toward the poles.

These signals precede extratropical climate changes by the North Atlantic Oscillation and Extratropical Jet Stream. These new findings point to a source of long-range predictability from within the atmosphere that will help us understand and better predict weather and climate.

Professor Scaife added: “We usually look to the ocean for long-range signals, but these new results show that long-range predictions can also be made from within atmosphere.”