Archives par mot-clé : Weathering

Earth can regulate its own temperature over millennia, new study finds

by Massachusetts Institute of Technology, Nov16, 2022 in ScienceDaily

The Earth’s climate has undergone some big changes, from global volcanism to planet-cooling ice ages and dramatic shifts in solar radiation. And yet life, for the last 3.7 billion years, has kept on beating.

Now, a study by MIT researchers in Science Advances confirms that the planet harbors a “stabilizing feedback” mechanism that acts over hundreds of thousands of years to pull the climate back from the brink, keeping global temperatures within a steady, habitable range.

Just how does it accomplish this? A likely mechanism is “silicate weathering” — a geological process by which the slow and steady weathering of silicate rocks involves chemical reactions that ultimately draw carbon dioxide out of the atmosphere and into ocean sediments, trapping the gas in rocks.

Scientists have long suspected that silicate weathering plays a major role in regulating the Earth’s carbon cycle. The mechanism of silicate weathering could provide a geologically constant force in keeping carbon dioxide — and global temperatures — in check. But there’s never been direct evidence for the continual operation of such a feedback, until now.

The new findings are based on a study of paleoclimate data that record changes in average global temperatures over the last 66 million years. The MIT team applied a mathematical analysis to see whether the data revealed any patterns characteristic of stabilizing phenomena that reined in global temperatures on a geologic timescale.

Journal Reference:

  1. Constantin W. Arnscheidt, Daniel H. Rothman. Presence or absence of stabilizing Earth system feedbacks on different time scales. Science Advances, 2022; 8 (46) DOI: 10.1126/sciadv.adc9241

More ‘reactive’ land surfaces cooled the Earth down

by Charles the moderator , July 6, 2019 in WUWT

Higher reactivity could explain temperature drop before last ice age

GFZ GeoForschungsZentrum Potsdam, Helmholtz Centre

From time to time, there have been long periods of cooling in Earth’s history. Temperatures had already fallen for more than ten million years before the last ice age began about 2.5 million years ago. At that time the northern hemisphere was covered with massive ice masses and glaciers. A geoscientific paradigm, widespread for over twenty years, explains this cooling with the formation of the large mountain ranges such as the Andes, the Himalayas and the Alps. As a result, more rock weathering has taken place, the paradigm suggests. This in turn removed more carbon dioxide (CO2) from the atmosphere, so that the ‘greenhouse effect’ decreased and the atmosphere cooled. This and other processes eventually led to the ‘ice Age’.

In a new study, Jeremy Caves-Rugenstein from ETH Zurich, Dan Ibarra from Stanford University and Friedhelm von Blanckenburg from the GFZ German Research Centre for Geosciences in Potsdam were able to show that this paradigm cannot be upheld. According to the paper, weathering was constant over the period under consideration. Instead, increased ‘reactivity’ of the land surface has led to a decrease in CO2 in the atmosphere, thus cooling the Earth. The researchers published the results in the journal Nature.

Studying oxygen, scientists discover clues to recovery from mass extinction

by Arizona State University, April  17, 2018 in ScienceDaily

About 252 million years ago, more than 90 percent of all animal life on Earth went extinct. This event, called the “Permian-Triassic mass extinction,” represents the greatest catastrophe in the history of life on Earth. Ecosystems took nearly five million years to recover and many aspects of the event remain a mystery.

A research team, led by scientists from Arizona State University and funded by NASA and the National Science Foundation, is helping to understand why this extinction event happened and why it took life so long to recover. The study, published in Science Advances, was led by ASU School of Earth and Space Exploration graduate student Feifei Zhang, with direction from school faculty member Ariel Anbar.