Meeting Documents

Impact of Terrestrial Climate Change on Tidal Dissipation and Lunar Orbit Evolution

Abstract

Small changes in M2 ocean tide over the past three decades have been detected through satellite altimetry data and reproduced by numerical tidal modeling (Opel et al., 2024; Ray and Schindelegger, 2025). These trends have been attributed to sea-level rise and enhanced ocean stratification driven by climate change-induced warming of the ocean. In this study, we use Lunar Laser Ranging (LLR) observations of the Earth Moon distance to estimate the change in global tidal dissipation, which is a direct consequence of tidal torque slowing Earth’s rotation. In standard tidal models for LLR, time delay parameters, representing the lag between the gravitational forcing by the Moon or Sun and Earth’s dissipative tidal response, are treated as constant over the period of observation. We revise this approach by allowing for a fractional variation in the time delays over the years, presumably caused by climate change. Using 55 years of LLR data (1970–2025), including recent measurements from the Next Generation Lunar Retroreflector-1, we provide an independent estimate of the tidal dissipation rate, complementing those derived from altimetry and ocean modeling. We find that tidal dissipation associated with the M2 component has decreased by approximately -0.05 ± 0.03% over the past 30 years. When compared to dissipation values from altimetry and numerical models, our results are consistent in sign and within a factor of four of each other. This study presents converging evidence from three methods indicating a weakening of global tidal dissipation in the last decades due to climate change, coupling orbit evolution and ocean tide models. Furthermore, LLR data offer the first evidence of climate change effects beyond Earth, manifested in a reduced lunar recession rate and enhanced secular motion of the Moon.

Plain-language Summary: Small changes in ocean tide over the past three decades have been detected by satellite altimetry observations and reproduced by ocean simulations. These trends have been attributed to climate change-induced warming of the ocean, which is raising sea levels and altering their layered structure. In this study, we use Lunar Laser Ranging (LLR), which measures the distance between the Earth and Moon, to track changes in tidal energy loss caused by tides slowing Earth's rotation. Standard tidal models assume this energy loss is constant over the period of LLR observation. We revise this approach by allowing slight changes over the years, presumably from climate change. Analyzing 55 years of LLR data (1970–2025), we find that tidal energy loss decreased by approximately -0.05 ± 0.03% over the past three decades, partially matching the results from altimetry and ocean simulations. Together, the evidence suggests that climate change is causing Earth’s tides to weaken, but also slowing down how fast the Moon moves away from Earth. Our study provides the first evidence of climate change effects beyond our planet, manifested in the Moon’s orbital motion.