65 million years of Climate Change

Nobody explains it as well as Dr. Jeremy Rugenstein of ETH Zurich.

This is a cut-n-paste from ETH Zurich on his work:

Fossil soils hold climate data

Instead of focusing on the future, Rugenstein is travelling millions of years into the past, analysing fossil soils in order to uncover information about the prehistoric climate. “By looking into the past – a time when the atmosphere contained much more carbon dioxide – we can understand how the climate behaves with different CO₂ concentrations, allowing us to predict our future climate,” he explains.
This research field is known as palaeoclimatology. For his doctoral thesis, the young American researched the prehistoric climate in Central Asia. He demonstrated how we can deduce the amount of precipitation and abundance of vegetation in the past by using mass spectrometric analyses on sedimentary rock. “Plants are a key climate factor, because their water absorption and release determines how much water is available on the earth,” he says.
The geochemist uncovered information about the state of prehistoric vegetation by analysing the fossil soils in which these plants once grew. During root respiration, these plants left behind CO₂, which still remains in the soil today in the form of calcium carbonate. This mineral, particularly the carbon and oxygen isotopes it contains, enables Rugenstein to draw conclusions about the past: the carbon reveals how much vegetation grew, and the oxygen reveals the amount and even the origin of rain.

Climate change over the past 65 million years

The 30-​year-old researcher is primarily interested in fossil soils from the most recent geological time period, the Cenozoic era, which encompasses the last 65 million years – in other words, from the dinosaurs’ extinction through to the present day. His teaching experience becomes obvious when he begins describing the geological era during which mammals and flowering plants began spreading across wide landmasses.

“It was warmest around 50 million years ago.

 It’s very likely that there were no

 landmasses on earth permanently covered in ice.

 We had palm trees in Antarctica and

 crocodiles frolicking around Greenland,”...

       

...why since then, average temperatures have fallen

 by ten to fifteen degrees Celsius

 and the carbon dioxide content

 in the atmosphere has fallen

 from around 2,000 parts per million to under 400.

 
Rugenstein

 

“It was warmest around 50 million years ago. It’s very likely that there were no landmasses on earth permanently covered in ice. We had palm trees in Antarctica and crocodiles frolicking around Greenland,” says Rugenstein, describing the scenery of that time period. He is particularly interested in why “It was warmest around 50 million years ago. It’s very likely that there were no landmasses on earth permanently covered in ice. We had palm trees in Antarctica and crocodiles frolicking around Greenland,” says Rugenstein, describing the scenery of that time period. He is particularly interested in why since then, average temperatures have fallen by ten to fifteen degrees Celsius and the carbon dioxide content in the atmosphere has fallen from around 2,000 parts per million to under 400.

Volcanoes and marine organisms

The young scientist, who is clearly pursuing an academic career, is currently focusing on the weathering of rock and understanding how this process is linked to the atmosphere’s CO₂ content.
He explains: “In a world without modern, industrialized society, most of the carbon dioxide in the atmosphere comes from volcanoes. However, the majority of it is then removed again by the weathering of rock.” In short, it works as follows: CO₂ dissolved in rainwater creates acid and reacts with silicate rock. This produces bicarbonate, which is washed into the ocean in the course of the water cycle. Marine organisms, such as corals, absorb the bicarbonate and use it to build reefs. As a result, the CO₂ is taken out of the global carbon cycle for a long time.

New perspectives at ETH

To better understand the role of silicate rock weathering in the carbon cycle, Rugenstein has been carrying out research since January 2017 as an ETH Fellow in the Earth Surface Dynamics group. His work includes puzzling over computer models used to simulate weathering processes.
As a geochemist, Rugenstein has found it enriching to be surrounded by geophysicists in his research group at ETH. He enjoys considering his research questions from different perspectives and bringing his own expertise to other research fields. For this reason, he attaches great importance to connecting with other researchers. With that in mind, he considers the relatively large size of the ETH research group with which he works to be more of a disadvantage: “I’m rarely able to discuss my work with scientists outside of the group.”

Volcanoes and marine organisms

The young scientist, who is clearly pursuing an academic career, is currently focusing on the weathering of rock and understanding how this process is linked to the atmosphere’s CO₂ content.
He explains: “In a world without modern, industrialized society, most of the carbon dioxide in the atmosphere comes from volcanoes. However, the majority of it is then removed again by the weathering of rock.” In short, it works as follows: CO₂ dissolved in rainwater creates acid and reacts with silicate rock. This produces bicarbonate, which is washed into the ocean in the course of the water cycle. Marine organisms, such as corals, absorb the bicarbonate and use it to build reefs. As a result, the CO₂ is taken out of the global carbon cycle for a long time.


More reading:
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Greenland and Northern Hemisphere Ice Sheets

My love of all things geology often leads to the most interesting reads, mostly on the internet.

From a couple of searches on the internet today on Earth Surfaces Dynamics--beginning with structural geology--the following very interesting site, from the Climate Geology section of ETH Zurich was found.

I could read this stuff for hours and hours, lost in science and exploration.
But some things needed to be cut-n-pasted, due to their relevance to discussions being held today, so here goes:

"The Climate Geology group studies how the Earth’s climate system has responded in the past to different levels of atmospheric CO2, solar energy, and frequency of volcanic events.

We obtain climate information from stalagmites and microfossils from ocean and lake sediments. These records elucidate how the earth’s climate system works, and better predict the climate response to anthropogenic changes.  (anthropogenic: adjective adjective: anthropogenic (chiefly of environmental pollution and pollutants) originating in human activity.

How easy is it to melt the Greenland and Northern Hemisphere ice sheets?

The Greenland ice sheet melted back to less than half its current size, around 125,000 years ago. Consequently, sea levels were at least five meters higher than now. We are investigating how changes in solar energy, greenhouse gases, and ocean currents contributed to melt the Greenland and northern hemisphere ice sheets.
We study indicators of climate in stalagmites that grew in caves of northwest Spain throughout the last several hundreds of thousands of years. Each year, rainwater infiltrating into the cave lays down a thin layer of mineral on the stalagmite. We carefully sample these layers and analyze their elemental and isotopic composition. From this we can learn about the size of large ice sheets, the temperature, and amount of rainfall during the time each layer was deposited. By knowing the exact age, we can precisely compare the climate with calculations of how the solar energy changed in different seasons due to slow cyclical changes in the earth’s orbit around the sun.
We can also investigate how the melting of the ice sheets affects the ocean currents in the North Atlantic, which in turn influence climate. Since the Greenland ice sheet may be vulnerable to anthropogenic warming, these results help predict future climate."

and there's more:

"How sensitive is earth’s climate to atmospheric CO2?

Tree pollen around Antarctica and records of 26 degree oceans off New Zealand, suggest that earth was much warmer than present 50 million years ago. Then about 33 million years ago, the Antarctic Ice sheet, with ten times more ice than Greenland, grew and expanded out to the coast of Antarctica. Changing levels of atmospheric CO2 are often invoked to explain these changes. But how high was CO2 when Antartica was ice free and covered with coastal forests? What was the critical CO2 level when the Antarctic ice sheet formed? And at what CO2 level has significant meltback occured? More generally, how sensitive is the earth’s climate to atmospheric CO2 levels?
To answer these questions, we are working to develop better ways to estimate atmospheric CO2 levels in the distant past. Marine algae need CO2 for photosynthesis, and the isotopic composition of organic and mineral fossils they produce can reveal the level of CO2 limitation they experienced. We use the fossils of microscopic algae that accumulate in sediments at the bottom of the ocean. Cores of sediments taken from hundreds of meters below the sea floor allow us to sample and analyze these fossils. Our work so far has revealed a previously undetected CO2 decline accounting for a strong cooling between 10 and 6 million years ago.
The size and shape of the fossils themselves also reveal adaptations to CO2. We use high resolution microscopy with digital cameras to see measure changes in the size and the thickness of the calcite mineral shells that covered the algae. Finally, we are using some known indicators, and working to ground-​truth new ones, to infer the ocean temperatures from the tropics to the poles, during these past periods of high CO2.
Our group is not always stuck in the deep marine muds. To better understand how marine algae record CO2 conditions, and at the same time better understand how the algae adapt to changing levels of CO2, we grow marine algae in an experimental growth chamber under different levels of CO2, light, and nutrients.

Climate extremes on the land

The estimation of past temperatures is one of the fundamental goals of paleoclimate research. We are working to improve the measurement precision and calibration of a widely applicable “paleothermometer” based on the increased clumping of heavy isotopes 13C and 18O in minerals at low temperatures. With this tool, we are able to estimate how hot summer temperatures were on land 50 million years ago, and how much warming came from ancient cycles in volcanic CO2 release in the era of the dinosaurs.

The Climate Geology group at ETH Zurich is led by Heather Stoll"

Professor Dr. Heather Stoll

ETH Zurich

Professur für Klimageologie

Prof. Dr. Heather Stoll

NO G 55, Sonneggstrasse 5

8092 Zürich, Switzerland

Fascinating stuff.
Excellent website from ETH Zurich!

I'll be reading that website more thoroughly...