Great Geologists | 91
Milutin Milanković
That climate changes naturally through time and on different
time-scales has long been understood. 19th century geologists
were well aware that Earth’s past climates were different from
today. Initially, global climates were viewed as changing on a long
term basis (the Cretaceous period being warmer than today for
instance), but with the recognition by Louis Agassiz and others
of ice ages in the relatively recent past, it became apparent that
climate change could also be short-term. How quickly climate
might change and the associated driving mechanisms were
uncertain, although it was suspected that variations in Earth’s
orbital parameters creating changes in solar insolation (the
amount of energy received from the Sun) might be at least in
part responsible.
This conundrum was effectively solved in the first half of the
20th century by the outstanding Serbian scientific polymath,
Milutin Milanković (often spelt in anglicised form as Milankovitch).
Laborious calculations permitted Milanković to determine that
cyclic variations in Earth’s orbital parameters could profoundly
control climate on scales ranging from tens of thousands
to hundreds of thousands of years. Milanković’s work was
challenged because age-dating of rocks was in its infancy at the
time he was publishing his ideas, meaning they could not be
tested. Furthermore, the changes in insolation that he proposed
as the driving mechanism for climate change were considered
too small to be significant.
However, in the 1970s his work was rediscovered by
paleoclimatologists and validated by data from deep-sea
sediment cores and cores from ice sheets. It now forms a central
pillar of our understanding of Earth’s past climates and is used
to explain some of the cyclicity seen in the sedimentary record.
In turn, this cyclicity can be used to develop high-resolution
timescales. Without an understanding of ‘Milankovitch Cyclicity’
our knowledge of Earth system science would be significantly
poorer.
Milutin Milanković photographed whilst a student in Vienna.
Milanković was born in 1879 in Dalj, a village on the banks of
the Danube, in what is now Croatia. An able student, he moved
to Vienna in 1896 to study civil engineering at the Vienna
University of Technology. He graduated in 1902 and, after a year
of military service, returned to the university to study for a PhD
entitled ‘The Contribution to the Theory of Pressure Curves’.
His PhD was quickly obtained before the end of 1904 and he
then embarked on a career in construction engineering. Whilst