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30

I'm not quite sure if the question is asking about glacial, ice ages, or snowball Earth, and whether it's about the onset or end of a glacial period. I'll try to hit all three. Ice Ages and Milankovitch Cycles Ice ages are long spans of time that marked by periods of time during which ice reaches far from the poles, interspersed by periods during which the ...


19

I think you're slightly confused by some of the terminology. (Caveat: I'm a geophysist, take anything I say with a grain of salt!) We're currently in an interglacial during a prolonged period of icehouse climate (most of the Cenozoic). During most of the Earth's history, the overall climate tends to be much warmer and more stable on the million-year scale....


17

I'm going to try to answer this, though it's actually a very hard question depending on how close you look at it. Lets start with the American Physical Society's statement on climate change - which, they've made an effort to balance out following their 2007 statement of "evidence is incontrovertible" that got some members upset and lead to a handful of ...


15

Of course it isn't "absurd", and looking at the ball-park energy budget figures you'll see why: First, I don't think anyone is claiming the Earth is completely frozen. More of a "slushy at the Equator" scenario. But let's assume an average 1 km thickness of ice for arguments sake (i.e. probably an exaggeration although polar ice would be thicker). The ...


13

Essentially, we can't. At a meeting some years ago, different specialists tried to define the onset of glaciation and found that each (sub-) discpline had their own definition. An oceanographer boldly stated the glaciation started 2000 years ago since a change in the Greenland ocean currents occurred at that time which was observed to also change before the ...


12

It depends where, the continental landmasses at higher latitudes would be covered by massive ice sheets. Therefore the life in the sections of the US and Europe that are close to the Ice sheets would have conditions similar to what is life in Greenland today. The map would look like this: (Image taken from planetaryvisions.com) And the summers would be ...


12

The most accepted theory is that the Younger Dryas was caused by a large reduction or shutdown of the North Atlantic "Conveyor" because of a sudden influx of fresh water from Lake Agassiz and deglaciation in North America. (Although evidence for such an event is thus far lacking.) The global climate would then have become locked into this new state until ...


11

If I understood it correctly, the important point is the temperature difference between mars and earth. On earth increasing obliquity, as you wrote, leads to increased melting of ice, ie. you increase the amount of liquid water on earth. On mars average temperatures even during summer are too low to allow for liquid water. Higher obliquity doesn't really ...


10

This question (if you can call it like this) is not even wrong. Let's ignore the fact that the title has little to do with the actual content of the question. Let's discuss your statement: If this occurred 120,000 years ago and seems to be taking place again, Man is not the cause behind Greenland's glacial melting. There is no logical part between the ...


10

No, solar activity will not help offset anthropogenic warming in any significant way. Recent research says a grand solar minimum would cause no more than 0.3C cooling over the 21st century [Feulner & Rahmstorf (2010), Jones et al. (2012), Anet et al. (2013)] But to see the influence of the solar cycle on the earth's climate together with the effect of ...


10

In addition to the theories mentioned by Azzie Rogers, there is another intriguing (but highly tentative) hypothesis: the YD may have been triggered by a large cosmic impact event. The results of a major study of impact-derived spherules at the time of the YD were recently published by Wittke et al. (2013). I should reiterate, though, that this is not ...


10

I will answer mostly from archaeological perspective; I don't know much about the paleoclimatology before the first people started to produce stone tools. I know just some basics of other disciplines where they affect human (pre)history, but it might help. First, even though longer and older cold periods are also refered as "ice ages", most people don't ...


9

The link between orbital parameters and CO2 levels is, as you wrote, the temperature. Orbital parameters may change, via feedback mechanisms, the atmospheric temperature. To my knowledge the most important feedback mechanism with respect to the Milankovich cycles is the ice-albedo feedback. The temperature, however, is an important player in geochemical ...


9

These claims originate with a paper by a mathematician named Valentina Zharkova and others, who studied a correlation between solar magnetic fields and sunspots. Based on the last three solar cycles, her model predicted that the next several solar cycles will be less intense than typical (i.e. fewer sunspots), which implies lower radiant output. Here is an ...


7

The "mini ice age" hypothesis is hype (note the lack of references to supporting peer-reviewed literature). For scientific information on its possibility, see this GRL article by Meehl et al. (2013). From the abstract: A future Maunder Minimum type grand solar minimum, with total solar irradiance reduced by 0.25% over a 50 year period from 2020 to 2070, ...


6

The Earth's climate switches between "hothouse Earth", where ice is nearly absent worldwide, and "icehouse Earth" where the Earth intermittently has ice that stretches far from the poles. Periods when the Earth is in the icehouse Earth phase are called ice ages. The most recent ice age began about 2.6 million years ago and has not yet ended. We are still in ...


6

Your question is framed as if any model of glaciation were only allowed to consider one of those influences. I think practically any palaeoclimatologist would accept that astronomical forcing, solar output, and volcanic eruptions all have effects on glaciation. It's true, however, that on long timescales (tens of kiloyears and up), Milankovitch forcing ...


6

The Quaternary is definitely a good guess. But it is difficult to answer your question because the "age of a fjord" is a rather ambiguous concept. Also, I'll asume you are interested in the bedrock topography associated to the fjords, and not only the sea inlets (as in that case they would have formed very recently, just when the glaciers receded enough to ...


6

A frost-gley is a waterlogged permafrost soil. IOW, a gleysol that has undergone cryoturbation.


5

First, great question, though answers are likely to be non specific and speculative. As far as I understand, we are currently living in the Holocene, an interglacial period of the Quaternary glaciation, i.e. the current ice age that has so far lasted 2.6 million years. The Holocene began about 12,000 years ago. While humans emerged about 200,000 ...


4

As has been abundantly said in the comments and on meta, there is no proper answer to this question in the current state of knowledge. But indeed we can at least check if we can come up with a rough estimate (and thus try to see from where this 20% estimate comes from). Let's first look at the main known glaciations: The Current one: there is indeed a ...


4

I understand following comment as part of your question: Was that climate and terrain habitable by prehistoric humans? I also assume that by "interglacial periods" you don't mean the last and current one, the Holocene. The next latest one is Eemian. The wikipedia sais on the sea level during that period: Sea level at peak was probably 4 to 6m (13 to ...


2

First, let us try to understand how precession affects climate: The precessional effect on climate is caused due to two factors:- (1) Axial Precession (2) Apsidal Precession The precession of the apses doesn't cause a change in climatic state by itself. However, this motion is in the same sense as the axial precession (gyroscopic motion of the earth's axes)...


2

The changes of climate in the past you're talking about occurred mainly because of the periodic change of earth's movements relatively to the sun. For example the swinging rotational axis of the earth and the changing orbit (sometimes a very flat ellipsoid, then again more like a circle) around the sun. This leads to the periodic change you were talking ...


2

To be sure about why it appears to be centered around -0.2°C, you'd have to go to the original source of the graph. However, as an educated guess, I would imagine that they are showing the anomaly compared to some recent period, such as 1961-1990 or 1971-2000, as is commonly done. From your Wikimedia Commons link, this figure appears to be original work by ...


2

I'm guessing this has been answered before, but in a nutshell, the primary mechanism over the last 3 million years or so is nothing more than colder summers in the Northern Hemisphere. Now, one cold summer won't do it, you need hundreds, which usually requires an orbital variation or perhaps, ocean current change or perhaps an extended solar minimum, but ...


2

In a short timescale, let's say one or two years after a permanent equinox state, the temperature would be basically the current mean annual temperature. This is because if we take the premise of keeping heat transport by convection (on the sea and the atmosphere) as it it today, the total energy inputs and outputs would be the same. Therefore, the same mean ...


2

A small meteor/asteroid impact might trigger a nuclear winter, but it would be registered by people and it would be very unlikely to trigger an ice age unless the impact created a very large amount of dust in the atmosphere. The dust would need to stay in the atmosphere for a decade or more to trigger an ice age. A natural nuclear explosion cannot be very ...


1

Ok, I am answering to myself: here are the papers, everything is in there https://www.nature.com/nature/journal/v423/n6942/full/nature01690.html https://www.nature.com/ngeo/journal/v3/n2/full/ngeo729.html


1

"Why is the y-axis centered around -0.2 °C?" It's not. The anomaly graph is actually centered at 0 degrees and a particular date, probably the late 1970s, as Gerrit alludes to. Where the axes cross is unimportant. The bottom end of this plot has been expanded to show negative anomalies (everything BELOW 0 degrees) as well as the positive anomalies (...


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