Is Earth-moon tidal friction causing global warming?
Is the dissipation of energy in the form of tidal friction in the Earth-moon system causing global warming?
Recent global warming has occurred in the geologically instantaneous period of about a hundred years at a rate much higher than is typical over much of Earth’s history. In contrast, the Moon has been receding constantly since its origin ~4.5Ga ago and its rate of recession has increased only over geologic time scales, not over intervals as brief as 100a. Furthermore, Earth has gone through climate cycles in the past as marked by ice ages. This lack of coherence between the constantly increasing Earth-Moon distance and climate cycles on Earth is evidence that the recession of the moon is not a direct factor in modern global warming.
However, the recession of the moon, presently about 4 cm/a, is estimated to transfer about 3TW to Earth primarily in the form of energy dissipation by the friction between ocean tides and rest of Earth. Observations suggest that nearly 30% of the tidal energy budget may actually be distributed in the deep oceans and help sustain deep ocean currents. Since both deep and near-surface ocean currents are key moderators of global climate change, the recession of the Moon may be an important factor in the stability of the climate, even though it does not contribute to global warming.
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