This piece is part of a collection of sound compositions called Timescales, which sonifies datasets spanning different time scales of the atmospheric carbon record. Glaciations is a musical sonification of atmospheric carbon dioxide inferred from ice cores, from 800,000 years ago to the present. This scale encompasses the small shifts in earth’s orbit which drove the rise and fall of eight successive ice ages and alternating warm periods. The intention behind the compositional choices in this composition is to evoke a sense of vastness and wonder, and to create a sonic landscape of planetary motion and deep time.

Glacial cycles are the central organizing feature of this composition. Historical time is linearly mapped to musical time: one beat in musical time represents 2,000 years. The carbon record is mapped to a pentatonic scale spanning six octaves, with 170 ppm and 420 ppm at the lower and upper limits, respectively, of CO₂ measurements. 

A simple sine wave tone glides up and down to sonify CO₂. Three additional longer sonic layers rise and swell with each successive interglacial warm period, all using FM synthesis. One layer is a beating sound, with three or four beats per data point. The carrier frequency of this sound is set by the first value of CO₂ in the cycle, and stays constant for the duration of the cycle.  A second layer is sustained over three data points, or approximately 6,000 historical years. This sound is created with complex modulation FM synthesis. The carrier frequency is one octave below the CO₂ value.  A third sound is held over the duration of the whole glacial cycle. This is made with a complex carrier frequency set, as with the first layer, by the first CO₂ value in the cycle. 

The final data point, which represents the present-day CO₂ value, is held longer than the others, and fades away. This was an aesthetic choice not to cut off the sound too abruptly, but allow the high frequency. It is almost a comical sound in contrast to the rest of the piece, intentionally disjointed. 

Carbon Dioxide Records are from:

• Rubino, Mauro; Etheridge, David; Thornton, David; Allison, Colin; Francey, Roger; Langenfelds, Ray; Steele, Paul; Trudinger, Cathy; Spencer, Darren; Curran, Mark; Van Ommen, Tas; Smith, Andrew (2019): Law Dome Ice Core 2000-Year CO2, CH4, N2O and d13C-CO2. v1. CSIRO. Data Collection. https://doi.org/10.25919/5bfe29ff807fb
• Lüthi, D., M. Le Floch, B. Bereiter, T. Blunier, J.-M. Barnola, U. Siegenthaler, D. Raynaud, J. Jouzel, H. Fischer, K. Kawamura, and T.F. Stocker. 2008. High-resolution carbon dioxide concentration record 650,000-800,000 years before present. Nature, Vol. 453, pp. 379-382, 15 May 2008.

This is a stereo wav file and can be played through any digital music player.