NICHOLAS SHACKLETON was a geologist who made fundamental contributions to Quaternary paleoclimatology (the study of past climates throughout geologic and historic times and why they vary) and palaeoceanography (the study of oceans in the geologic past). The Quaternary period is the most recent geological period of time in the history of the Earth, covering roughly the last 1.8 million years up to the present day. The Quaternary period includes a series of very extensive environmental changes that have greatly affected and shaped the landscapes and life on Earth.

During the Quaternary, major continental ice sheets and mountain ice caps have built up from time to time, during long glacial stages. These have been interspersed with warm periods each lasting a shorter time, during which the temperature was similar to or higher than those today. But for long periods of the climatic cycles of the Quaternary — there have been probably roughly 40 of them — the temperatures were cold.

Knowledge and understanding about how the climate has changed over the past is crucial for those trying to predict future climatic changes more reliably. Shackleton made significant contributions to this by identifying the glacial-interglacial climatic changes, particularly the role of carbon dioxide and changes in the Earth’s orbit in causing them. Shackleton also developed a method of analysing more accurately the fluctuations in the size of ice sheets that often developed during the Quaternary.

He warned us that if we significantly increase our emissions into the atmosphere of gases that cause global warming we may trigger a rapid change in the future climate similar to those that have happened in the past. The human race, he said, must make serious efforts to control the release of greenhouse gases: a timely warning in light of the recent international concerns about global warming.

Shackleton also made significant original contributions to the scientific understanding of the processes in the oceans. For this work, he developed new methods for analysing very small samples using a mass spectrometer. He modified the device so that it could analyse tiny fossils that are found in the cylindrically shaped cores drilled out of the sediments on the ocean floor.

Using samples from the Pacific Ocean, he compared the isotopes of oxygen in shells of species living near the ocean surface and those that lived at great depth. He showed that the glacial-interglacial range of isotopic values in the shells were very similar. From his results, he deduced that changes in the global ice volume were much more important than changes in water temperature. This laid to rest a long and sometimes acrimonious debate about which of these two factors dominated.

In 1973 Shackleton analysed a sediment core from the western tropical Pacific that contained evidence of the most recent reversal of the Earth’s magnetic field which occurred about 780,000 years ago. From time to time the Earth’s magnetic field reverses or “flips”. When this happens, the North Pole is transformed into a South Pole and the South Pole becomes a North Pole. In the past ten million years, there have been, on average, four or five reversals per million years. A complete reversal may take between one and several thousand years to complete.

Shackleton did his ocean drilling aboard the Glomar Challenger, a ship built for scientific exploration and used for this purpose between August 11, 1968, and November 11, 1983. A length of pipe, up to 6.24km (3.9 miles) long, was suspended from the ship down to the bottom of the sea; a depth of up to 1.3km (0.81 miles) could be penetrated through the ocean bottom.

By reconstructing the history of global ice volume through the succession of Ice Ages, it became clear that ice-volume cycles occurred roughly every 100,000 years. Shackleton then knew, when he analysed ocean sediment cores, that each successively older Ice Age cycle could be correlated with the corresponding cycle in the first core. He had discovered a method for assigning an age scale, based on the 100,000-year cycles in the first core.

An important aspect of Shackleton’s results was that they supported the Milankovitch hypothesis about the collective effect of changes in the Earth’s movements on its climate. The eccentricity (the shape of the Earth’s orbit), axial tilt (the tilt of the Earth’s axis as the Earth wobbles), and precession (the change in the direction of the Earth’s axis of rotation relative to the Sun) of the Earth’s orbit all vary in several patterns, resulting in roughly 100,000-year ice age cycles of the Quaternary.

In a famous scientific paper, published with J. D. Hayes and J. Imbrie in 1976 in the journal Science, Shackleton used his analysis of deep-sea sediments to validate Milankovitch’s idea. They were able to detect periodicities of 19,000 and 23,000 years, due to precessional changes; 40,000 years, due to axial tilt; and 100,000 years, due to eccentricity.

This was a very important discovery because it provided a precise way of constructing an age scale for sediment cores using all three of the Earth’s orbital periodicities together. This allowed Shackleton to give accurate dates for the reversals of the Earth’s magnetic field and for the evolution and extinction of marine organisms.

Nicholas John Shackleton was born in 1937. He was distantly related to Sir Ernest Shackelton, the Antarctic explorer, and his father was Professor Robert Millner Shackleton, FRS, an eminent field geologist. Nicholas Shackleton was educated at Cranbrook School, Kent. Following in his father’s footsteps, he decided to study geology, which he did at Clare College, Cambridge, graduating in 1961. In 1967 he received his PhD for a thesis titled The Measurement of Palaeotemperatures in the Quaternary Era.

In 1965 he was appointed senior assistant in research at Cambridge University, a position he held until 1972 when he became assistant director of research in the sub-department of Quaternary research at Cambridge. In 1988, he was appointed director of the sub-department. In 1995, he became director, Goodwin Institute of Quaternary Research, Cambridge, a post he held until 2004, when he retired.

Shackleton published more than 200 scientific papers on marine geology, the geological history of climate, and other topics. He taught and encouraged many young researchers, who greatly appreciated his highly positive attitude, and he was a major influence on Quaternary research.

He received many honours and awards. In 1985 he was elected a Fellow of the Royal Society and he was knighted in 1998, for services to Earth sciences. In 1990 he became a Fellow of the American Geophysical Union; in 1995 he was awarded the Crafoord Prize by the Royal Swedish Academy of Science; and in 2000 he was elected Foreign Associate of the US National Academy of Science.

He received the Wollaston Medal of the Geological Society of London in 1996; the Milankovitch Medal of the European Geophysical Society in 1999; the Ewing Medal of the American Geophysical Union in 2002; the Urey Medal of the European Association of Geochemistry and the Royal Medal of the Royal Society of London in 2003; the Vetlesen Prize, Columbia University in 2004; and the Founder’s Medal of the Royal Geographical Society and the Blue Planet Prize of the Asahi Glass Foundation of Tokyo in 2005.

He received honorary degrees from the universities of Dalhousie (1996), Stockholm (1997), and Padua (2002). In 1984 Cambridge University awarded him a doctor of science degree.

In addition to his studies of palaeoclimatology and palaeoceanography, Shackleton was a keen player of the clarinet. He had a large collection of clarinets and avidly studied the history of the instrument. He wrote articles in the New Grove Dictionary of Music and Musicians. Quaternary research was the major interest in his life; music was a very close second. In his words: “Both music and science are for me intensely human activities, and both have found me innumerable friends.”

A few weeks before he died, in a typically forward-looking gesture, he set up the Sir Nicholas Shackleton Visiting Fellowship in Paleo-Climate Research at his college, Clare Hall, Cambridge, investing considerable sums of his own money.

Shackleton’s first marriage, to Judith Carola Murray, was dissolved in 1977; his second wife, Vivien Anne Law, whom he married in 1986, died in 2002.

Sir Nicholas Shackleton, FRS, geologist, was born on June 23, 1937. He died on January 24, 2006, aged 68.