The Gold Medal is the Royal Astronomical Society’s highest honour and can be awarded for any reason, but usually recognises outstanding lifetime achievement. It was first awarded in 1824, with previous winners including Albert Einstein, Edwin Hubble, Arthur Eddington, and Stephen Hawking. Since 1964, two Gold Medals have been awarded each year: one for astronomy, and one for geophysics.

Tim said “I am delighted to receive this award. Throughout my career, I have always been very motivated to do something of practical importance for society, but in a way that used the sophisticated theoretical and mathematical techniques I had been trained in. It is wonderful to have this formally acknowledged”. 

Tim joined the University of Oxford and Jesus College as a Royal Society Research Professor in 2010, a scheme that recognises world-class researchers of great potential. One of his most influential contributions to atmospheric science is the development of ensemble forecasting, a method that only became possible with the advent of powerful computers.

Before this, weather forecasting was treated as a deterministic problem, where it was assumed that with enough observations in the initial conditions it was possible to predict the outcome with 100% certainty. But this failed to account for the intermittent instabilities that occur in chaotic systems like weather. During periods where intermittent instabilities are strong, uncertainties, no matter how small, can grow rapidly and destroy any chance of making reliable deterministic predictions.

Professor Palmer pioneered an approach where, instead of running a single forecast, a computer simulation of a weather system is run multiple times using slightly different starting conditions and equations. Comparing the outcomes of these different simulations produces an estimate of the forecast uncertainty and indicates how likely different weather events will be.

Not only did this revolutionise the field of weather forecasting, but ensemble forecasting has led to the development of a wide range of operational products, including tools that allow disaster relief agencies to take anticipatory action: sending food, medicine and even finance, ahead of an anticipated extreme weather event, rather than reacting after the event has happened.

More recently, Professor Palmer has researched how ensemble forecasting can help predict uncertainty in many other fields, including COVID-19, economic, and conflict prediction. His popular science book The Primacy of Doubt, published in 2022, introduced these ideas to a wider audience, by explaining how the geometry of chaos can help  make sense of uncertainty in a rapidly changing world.