Earth's rotation slows down - Climate change makes days longer
Climate Change Makes Days on Earth Slightly Longer: Study in "Proceedings" of the US National Academy of Sciences
According to a study in the journal "Proceedings" of the US National Academy of Sciences (PNAS), climate change is causing the days on Earth to be minimally longer. The melting ice in polar regions distributes itself in the world oceans, leading to a different mass distribution on Earth, which slows down the Earth's rotation, reports a research team. The climate-induced effect on the length of days is currently approximately 1.33 milliseconds per century.
If climate change is not contained, this effect could be greater than the influence of the Moon on Earth's rotation, explains the group led by Mostafa Kiani Shahvandi from ETH Zurich.
Tides on Earth
The gravitational force of the Moon generates tidal forces on Earth, which are mainly visible in ebb and flow. The "tussle" of the Moon with the Earth minimally slows down the Earth's rotation and extends the day.
Both the climate and the tides have a small influence on the Earth's rotation, which can be measured with modern satellites. Shahvandi and his team used computer models to determine the influence of the climate since 1900 and predict the future up to 2100. They considered various scenarios for the development of climate change.
The calculations of the scientists revealed that the climate-induced increase in the length of days in the 20th century has significantly fluctuated: between 0.31 milliseconds per century (1960-1980) and 1.00 milliseconds per century (1920-1940). "These fluctuations reflect the variable contributions of global surface temperature change, ice melt, changes in terrestrial water storage, and sea level rise, which have occurred in the 20th century," write the authors.
Melting ice in Greenland and the Antarctic plays a decisive role
The researchers have calculated an average climate-induced increase in the length of days of 1.33 milliseconds per century for the first two decades of the 21st century - statistically significant more than in the entire 20th century. According to the computer models, this increase is mainly due to the melting ice in Greenland and the Antarctic.
"These results show through their effect on the length of days that the mass transport from the poles to the equator due to climate change in the last two decades was unprecedented compared to the previous 100 years," explain the scientists.
The researchers also considered an effect that counteracts the mass redistribution caused by ice melt: mass movements in the Earth's mantle. Kilometer-thick ice presses the land masses of Greenland and the Antarctic into the fluid part of the Earth's mantle, where the Earth plates move. When the ice melts, the land masses become lighter and rise, as fluid Earth mantle flows underneath. The effect is currently calculated to be minus 0.8 milliseconds per century, which shortens the length of days.
Climate Crisis Overpowers Moon?
At the prediction for the year 2100, Shahvandi's team used a favorable scenario with a significant decrease in greenhouse gas emissions: This brought barely any changes in climate-dependent day length. In the RCP8.5 scenario, it was different: If the greenhouse gas emission continues to increase and the polar caps melt further due to climate change, a climate-dependent extension of the day by 2.62 milliseconds per century would result.
This effect would be greater than that caused by the tidal forces of the moon, which lead to a day extension of 2.40 milliseconds per century.
- The study in PNAS explains how climate change is causing the Earth's rotation to slow down, leading to slightly longer days.
- This effect is attributed to the melting ice in polar regions, such as Antarctica, distributing itself in the world's oceans.
- The Swiss Federal Institute of Technology Zurich (ETH Zurich) led by Mostafa Kiani Shahvandi conducted the research, highlighting the significant fluctuations in the increase in day length between different decades.
- Greenland and Antarctica play a decisive role in the current average climate-induced increase of 1.33 milliseconds per century in the first two decades of the 21st century.
- The study also considers the counteracting effect of mass movements in the Earth's mantle, caused by melting ice, which shortens the length of days.
- If greenhouse gas emissions continue to rise and polar ice caps melt further, the extension of the day due to climate change could surpass the tide-related extension caused by the Moon's gravitational force.
- This research strengthens the urgent need for global action to combat Climate Change and protect our planet from irreversible consequences.
- Zurich's Swiss Federal Institute of Technology and Academy of Sciences are contributing to the international community's efforts in understanding and mitigating the impacts of Climate Change and its effects on our planet.
