Questions tagged [paleoclimatology]

Paleoclimatology concerns climate and climate variability before the onset of instrumented measurements.

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126 views

Why was the ice age more severe in North America than in Eurasia?

I've been looking at reconstructions of the extent of ice at the last glacial maximum, while each map differs slightly (two shown below), most show a massive North American ice sheet, extending as far ...
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3 answers
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How were the sea levels around western Europe during the Medieval Warm Period?

The Medieval Warm Period (MWP) or Medieval Climatic Anomaly was a time from about 950 to 1250 when climate was warmer than in the timespans immediately before and after. My question is if this ...
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Have we looked for human-like signals in the geological record?

This is somewhat of a follow up to some interesting discussion here about using synthetic radioisotopes to define the start of the anthropocene. It is also sort of related to a question asked here, ...
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1 answer
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Verification statistic for ice core temperature reconstructions

1 Do ice core temperature reconstruction studies have a calibration step, or is the relationship between Oxygen-18 and mean global temperature considered linear enough that this is not required? 2 ...
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Underground temperature record

Max/min Thermometer readings from a weather station with Stevenson screen are subject to noise from many sources and represent the max/ min at that one point in space. It's well known that underground ...
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Reconstructing lake level from organic and magnetic sediment data

I would like to understand why any of the following conditions in a layer of a lacustrine sediment core appear to imply that the lake level was low at the relevant time: low C/N ratio low δ13C low ...
13 votes
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How did CO₂ originate on Earth before there was life?

To start life there has to be $\ce{CO2}$. $\ce{Solar energy + 6CO2 + 6H2O -> C6H12O6 (sugars) + 6O2}$ $C_6H_{12}O_{6} + O_2 \longrightarrow H_2O + {CO}_2 + \text{Energy}$ So to start this cycle, ...
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Why aren't diatoms' shells used as a temperature proxy, but foraminifera shells are?

Changes in oceanic oxygen isotope ratios (18O to 16O) are reflected in the shells of ancient foraminifera. However, I have not read of diatom shells being used, despite the fact that they were (and ...
17 votes
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Could the Paleocene–Eocene thermal maximum have been caused by intelligent life forms?

I was intrigued to learn recently of the Paleocene–Eocene thermal maximum from this blog of John Baez. For those who haven't seen, it's the sharp spike labelled "PETM" in this graph (from ...
12 votes
3 answers
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How were we able to measure carbon dioxide levels in earlier climates?

It is said that carbon dioxide levels were much higher during the Cretaceous and Eocene periods: which proxies are used to determine paleo-pCO2?
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how old are the gulf stream and the NAC?

After reading about the NAC (North Atlantic Current) weakening in the news, we got to wondering about its history and that of the gulf stream. Specifically, how and when did they start? Were there ...
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Will a new glacial age take place on Earth or Holocene will become a new climatic epoch?

Pleistocene shows a switch between glacial and interglacial ages. However, humanity is burning fossil fuels and increasing atmosphere's $\ce{CO2}$ content. Should we expect a new glacial age after ...
3 votes
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Does deforestation increase global temperatures or just local temperatures?

Did human-caused deforestation impacted climate and rainfall patterns in the past? I'm asking this because I don't know much about the impact of forest cover loss and evapotranspiration on global ...
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Biomes that existed during the Paleocene-Eocene Thermal Max (PETM)

I understand that you could fill multiple books with descriptions of the PETM and the mechanisms that incited the event. I have always wondered what regions of the world were covered in what types of ...
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2 answers
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How accurate are climate proxies in giving us a clear picture of global average temperatures throughout Earth history?

Since reliable modern records of climate only began in the 1880s, proxies provide a means for scientists to determine climatic patterns before record-keeping began, though it appears that the the ...
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From ice core analysis to temperature curves

In ice cores a lot of data are measured and analyzed and can be plotted versus depth, for example age of layers thickness of layers concentration of spurious gases concentration of solids delta ...
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What was the Amazon like during Green Sahara?

It is said that the Amazon rainforest receives up to half of its nutrients via mineral dust from the Sahara desert. But a few thousand years ago, the Sahara desert was much more fertile, having a ...
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1 answer
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Were Carboniferous plants more efficient sequestering $\ce{CO2}$ than present plants?

The Carboniferous was a period where CO2 levels fell drastically. Source: Geologic history of seawater: A MAGic approach to carbon chemistry and ocean ventilation I think the main reasons are ...
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Why is it that "With higher CO2, the dry gets drier and the wet gets wetter"?

The Phys.org article CO2 dip may have helped dinosaurs walk from South America to Greenland quotes Dennis Kent, "adjunct research scientist at Columbia University's Lamont-Doherty Earth ...
2 votes
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How many extreme shifts in climate has Earth gone through in its existence?

As the Earth formed, it went through cycles of essentially hotter and colder periods. Extremely volcanic times and ice ages, in feedback loops contributing to one another. CO2 swinging from high to ...
9 votes
6 answers
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Any historical examples of destructive climate warming?

Summation: Local cooling climate changes, since the last ice age seem relatively common and all seem to cause significant harm to human population. But I can't find instances of the reverse, warming ...
1 vote
1 answer
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How much of the Earth's surface was covered with water during the Mesozoic?

When the Earth was at its warmest, and there were no ice caps at all, not even during the winter, and thermal expansion meant a certain amount of water took up more space, what ratio of Earth's ...
4 votes
1 answer
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Frost in trees in the middle of summer (of 536)

It was so cold that frost formed inside trees in the middle of summer. Traces of this have been found in Russia, among other places. It is very rare for trees to freeze internally during the summer. ...
41 votes
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How it's possible to measure temperature 2000 years ago with such precision?

I saw this graph about the global temperature, it goes back for 2000 years. How is it possible to measure temperature 2000 years back with such a precision of like ~0.1 C? The image from Reddit post I ...
8 votes
1 answer
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Release mechanism for methane clathrate at the PETM

The Paleocene-Eocene Thermal Maximum (PETM) is a well-studied warming event near the Paleocene-Eocene boundary. It is characterized by its extreme warming rate: from onset to recovery the event lasted ...
17 votes
3 answers
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Is there any evidence for higher air pressures in the geological past?

I was curious about how the Earth's overall air pressure has varied over time, and tried to take a look around the internet. However, Google pops up a lot of sites with questionable science proposing ...
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Did climate cool down when underground hydrocarbons stocks formed?

As far as I understand, the dominant theory of modern climate change says that recent warming is mainly caused by the massive burning of hydrocarbons that used to be stored in solid form mostly ...
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Earth History Book

I'm a PhD student studying the (current) climate of the Earth. I'm also quite interested in the history of planet Earth, although I have little academic background in that area. Is there a good ...
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In the 800 kyr $\ce{CO_2}$ record, how detectable would a short-term peak be?

It is stated in https://cdiac.ess-dive.lbl.gov/trends/co2/ice_core_co2.html that the temporal uncertainty for the glacier $\small\mathsf{CO_2}$ records is less than $\small\mathsf{5~\%}$ at any given ...
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Would a volcanic winter trigger an oceanic "spring"?

There is large amounts of observations supporting the effects of volcanic eruptions on climate: A long term subtle warming effect due to $\small\mathsf{CO_2}$ and a short term, but more intense ...
5 votes
2 answers
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At least by theoretical biology - could there be, or should there have been, or was a "southern Taiga" on earth?

All data I have ever encountered about the Taiga "pole surrounding", vast, cold forests comprised mainly of Pinophyta trees, was about the ...
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Why rely on climate models as opposed to paleoclimate data?

Something I hear often from climate scientists, and indeed even politicians, is that we "don't understand climate change very well". And, I'm sure this is true since the climate is a complex adaptive ...
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Can any natural process explain this rate of CO2 increase? [duplicate]

Can any natural process explain this rate of CO2 increase? [![1000 years of CO2][1]][1] [1]: https://i.stack.imgur.com/MO0mK.png The prior similar question used different data as its basis. This ...
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Does anyone have any data indicating a faster rate of CO2 increase?

Pieter Tans 2019-10-07(lead scientist of NOAA's Global Greenhouse Gas Reference Network): Based on the best historical data that we have available CO2 is probably increasing at a rate at of least ...
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Is there any natural phenomenon that can account for the 100 fold faster CO2 rate increase?

"Based on the best historical data that we have available CO2 is probably increasing at a rate at of least 100 times faster than at any time in the last 800,000 years." Pieter Tans lead scientist of ...
3 votes
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If today's Earth becomes warmer, how will it compare to the Earth of the Cretaceous period?

Most pessimistic scenarios about climate change predicts a global rise of temperature of several Celsius degrees over the course of the 21st century if no action is taken. While such a shift in ...
8 votes
1 answer
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Is there conclusive evidence to refute an earlier oxygenation of the Earth's atmosphere?

The Great Oxygenation Event (sometimes called the Great Oxidation Event (GOE), as in the journal Nature) occurred around 2.2 to 2.45 billion years ago (Frei et al. 2009). However, in the article A ...
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Did the impact event that caused the Chicxulub-Crater definitively and single-handedly cause the Cretaceous-Paleogene extinction?

Opinions abound on the web. What is the state of the current science regarding this theory and what is the best evidence? Is the theory gaining or losing traction? If it's losing what's the best of ...
4 votes
1 answer
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3 Billion years ago, the earth is covered with Carbon Dioxide. Where did it go?

Oxygen gas began to appear on the earth surface about 2 billion years ago by photosynthesis. Carbon Dioxide was converted into carbohydrates in the process. Where did these carbohydrates go? If they ...
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1 answer
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What was the ocean circulation like during the time of Pangaea?

So Enderton and Marshall (2009) wrote an interesting paper on the ocean circulation of various aquaplanets covered with certain terrain: e.g. an aquaplanet with a small ridge of land that ranged from ...
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How do you interpret Oxygen Isotope changes?

In a paper I am reading, the authors note "large (5-7%) negative shifts in the oxygen isotopic composition of geologic proxy materials" (Davis 2008, pg. 102) in several regional basins. This is then ...
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What makes a nuclear winter so extreme and destructive?

This may be a sort of, pertinent to the times, and disturbing question, inspired by the difficulties surrounding North Korea and the situation with it and nuclear weapons. I've heard of this idea of "...
6 votes
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Geological evidence about climate change: has there ever been a period with a rate of climate change as great as it is today?

Most statistics about climate change are based on climate data over the last 150 year (as long as records have been kept). This seems irrelevant in terms of the geological time scale of temperature ...
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What was the density and composition of Earth's atmosphere during the Cretaceous warmest period?

There was time during the age of dinosaurs when the polar regions were ice free. The earth was obviously much warmer but a run-away greenhouse effect did not occur. This was most likely because the ...
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Why did the carboniferous period have so much atmospheric oxygen?

Even if all the carbon dioxide (which makes up less than 1% of the atmosphere) in the air were sequestered by plants, would the atmosphere not remain about 21% oxygen? Why did the carboniferous period ...
4 votes
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Did the Azolla Event 49 Million Years Ago Result in an Extinction Event?

55 million years ago, the world was literally a jungle. With such high temperatures, rainfall and humidity, life could proliferate. But 49 million years ago, something drastic happened: The Azolla ...
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How was the Marinoan Glaciation triggered?

The Marinoan Glaciation (a.k.a. Elatina Glaciation) was a glaciation that is thought to have occurred towards the end of the aptly-named Cryogenian period at ca. 650Ma. It is particularly known as one ...
19 votes
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How do we know that we are NOT in an "Ice Age?"

Historically, the earth has had five "Ice Ages" Each of them lasted millions, tens of millions, or hundreds of millions of years. The last ice age reportedly ended perhaps 10,000 years ago. That ...
4 votes
1 answer
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What caused the Carbon Dioxide Variations observed in the 800,000-year polar ice record?

I have seen several graphs showing the prehistoric temperatures and CO2 concentrations derived from ice-core data. My understanding is that CO2 and temperature correlate. I assume that Milankovich ...
4 votes
1 answer
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What are the ranges of natural (or pre-industrial era) levels of CO2 in the atmosphere in ppm and tons?

Are the levels of natural (before the industrial revolution) levels of CO2 and ppm known? Also as a related question, should the "natural" levels be considered before the industrial revolution or ...