Climate Record From Bottom of Russian Lake Shows Arctic Was (8°C) Warmer Millions of Years Ago
http://www.nsf.gov/news/news_summ.jsp?cntn_id=127897&org=NSF&from=news[font size=5]Climate Record From Bottom of Russian Lake Shows Arctic Was Warmer Millions of Years Ago[/font]
[font size=4]Unparalleled sediment record is "most continuous archive" of ancient Arctic climate[/font]
[font size=3]May 9, 2013
The Arctic was very warm during a period roughly 3.5 to 2 million years ago--a time when research suggests that the level of carbon dioxide in the atmosphere was roughly comparable to today's--leading to the conclusion that relatively small fluctuations in carbon dioxide levels can have a major influence on Arctic climate, according to a new analysis of the longest terrestrial sediment core ever collected in the Arctic.
"One of our major findings is that the Arctic was very warm in the middle Pliocene and Early Pleistocene--roughly 3.6 to 2.2 million years ago--when others have suggested atmospheric carbon dioxide was not much higher than levels we see today," said Julie Brigham-Grette, of the University of Massachusetts Amherst.
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She added that "this could tell us where we are going in the near future. In other words, the Earth system response to small changes in carbon dioxide is bigger than suggested by earlier climate models."
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Another significant finding is documentation of sustained warmth in the Middle Pliocene, with summer temperatures of about 15 to 16 degrees Celsius (59 to 61 degrees Fahrenheit), about 8 degrees Celsius (14.4 degrees Fahrenheit) warmer than today, and regional precipitation three times higher.
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http://www.sciencemag.org/content/early/2013/05/08/science.1233137.abstract
= new reply since forum marked as read
Magnetic North may have been to the South a million years ago. However, that doesn’t mean that the Arctic wasn’t at the top of the globe.
http://www.nasa.gov/topics/earth/features/2012-poleReversal.html
This animation (showing Pangaea breaking up to form the continents as we know them) is believed to have taken about 200 Million years.
http://www.nature.nps.gov/geology/usgsnps/animate/pltecan.html
Continental drift may be as fast as a few centimeters a year (let’s call it at most 10.)
http://www-spof.gsfc.nasa.gov/earthmag/reversal.htm
10,000,000 centimeters = 100,000 meters = 100 kilometers
So, let’s call it at most 62 miles in a million years.
(So, the continents haven’t moved very much in the last 1,000,000 years.)
The Earth has gone through long cycles of warming and cooling before. We are currently in a cool cycle, or an ice age, in which relatively brief periods of warming occur between longer colder stretches with very significant ice sheet expansions.
As the first graph shows, the Earth started cooling millions of years ago and steadily cooled for millions of years. It has done this before, and the current cool cycle is not the coolest such cycle known.
http://news.discovery.com/earth/oceans/snowball-earth-ocean-mixing-130307.htm
One of the theories about the current ice age is that the Tibetan uplift caused a long term change in the Earth's albedo, creating a cooling bias (as an ice/snow cap formed on this area). I think that's wrong, but who really knows.
The graphs labeled The Earth in the Past neither show as high a CO[font size="1"]2[/font] level, nor as high a temperature difference.
As for the question, “Millions of years ago, weren't various places different in terms of climate?” It’s not as if “3.6 to 2.2 million years ago” the Arctic was tropical, and the tropics were frozen.
The North and South poles are not cold because of the magnetic field of the Earth. They are cold because they don’t get as direct sunlight as the tropics.
http://scijinks.nasa.gov/weather-v-climate
The primary cause of a region’s climate is its latitude. At and near the equator (low latitudes), the Sun’s ray’s hit Earth’s surface almost head-on all year long. At the Poles (high latitudes), the sunlight hardly reaches the surface at all half the time, and when it does, it passes through the atmosphere at a steep angle. In the mid-latitudes, the climate is more moderate, with the angle of the Sun and length of day changing throughout the seasons.
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Schematic illustration of Earth's magnetic field. Credit/Copyright: Peter Reid, The University of Edinburgh
[font size=3] Scientists understand that Earth's magnetic field has flipped its polarity many times over the millennia. In other words, if you were alive about 800,000 years ago, and facing what we call north with a magnetic compass in your hand, the needle would point to 'south.' This is because a magnetic compass is calibrated based on Earth's poles. The N-S markings of a compass would be 180 degrees wrong if the polarity of today's magnetic field were reversed. Many doomsday theorists have tried to take this natural geological occurrence and suggest it could lead to Earth's destruction. But would there be any dramatic effects? The answer, from the geologic and fossil records we have from hundreds of past magnetic polarity reversals, seems to be 'no.'
Reversals are the rule, not the exception. Earth has settled in the last 20 million years into a pattern of a pole reversal about every 200,000 to 300,000 years, although it has been more than twice that long since the last reversal. A reversal happens over hundreds or thousands of years, and it is not exactly a clean back flip. Magnetic fields morph and push and pull at one another, with multiple poles emerging at odd latitudes throughout the process. Scientists estimate reversals have happened at least hundreds of times over the past three billion years. And while reversals have happened more frequently in "recent" years, when dinosaurs walked Earth a reversal was more likely to happen only about every one million years.
Sediment cores taken from deep ocean floors can tell scientists about magnetic polarity shifts, providing a direct link between magnetic field activity and the fossil record. The Earth’s magnetic field determines the magnetization of lava as it is laid down on the ocean floor on either side of the Mid-Atlantic Rift where the North American and European continental plates are spreading apart. As the lava solidifies, it creates a record of the orientation of past magnetic fields much like a tape recorder records sound. The last time that Earth's poles flipped in a major reversal was about 780,000 years ago, in what scientists call the Brunhes-Matuyama reversal. The fossil record shows no drastic changes in plant or animal life. Deep ocean sediment cores from this period also indicate no changes in glacial activity, based on the amount of oxygen isotopes in the cores. This is also proof that a polarity reversal would not affect the rotation axis of Earth, as the planet's rotation axis tilt has a significant effect on climate and glaciation and any change would be evident in the glacial record.
Earth's polarity is not a constant. Unlike a classic bar magnet, or the decorative magnets on your refrigerator, the matter governing Earth's magnetic field moves around. Geophysicists are pretty sure that the reason Earth has a magnetic field is because its solid iron core is surrounded by a fluid ocean of hot, liquid metal. This process can also be modeled with supercomputers. Ours is, without hyperbole, a dynamic planet. The flow of liquid iron in Earth's core creates electric currents, which in turn create the magnetic field. So while parts of Earth's outer core are too deep for scientists to measure directly, we can infer movement in the core by observing changes in the magnetic field. The magnetic north pole has been creeping northward – by more than 600 miles (1,100 km) – since the early 19th century, when explorers first located it precisely. It is moving faster now, actually, as scientists estimate the pole is migrating northward about 40 miles per year, as opposed to about 10 miles per year in the early 20th century.
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http://news.sciencemag.org/sciencenow/2011/05/who-needs-a-moon.html
by Govert Schilling on 27 May 2011, 3:55 PM
[font size=3]BOSTON—The number of Earth-like extrasolar planets suitable for harboring advanced life could be 10 times higher than has been assumed until now, according to a new modeling study. The finding contradicts the prevailing notion that a terrestrial planet needs a large moon to stabilize the orientation of its axis and, hence, its climate.
In 1993, French mathematicians Jacques Laskar and Philippe Robutel showed that Earth’s large moon has a stabilizing effect on our planet’s climate. Without the moon, gravitational perturbations from other planets, notably nearby Venus and massive Jupiter, would greatly disturb Earth’s axial tilt, with vast consequences for the planet’s climate. The steadily orbiting moon’s gravitational tug counteracts these disturbances, and Earth’s axial tilt never veers too far from the current value of 23.5°, where 0° would mean the axis was perpendicular to the plane of Earth’s orbit around the sun.
Indeed, Laskar and Robutel also showed that the axial tilt of Mars, which has only two tiny moons, has varied between 10° and 60° in the past, which caused huge climate variations that in turn could have contributed to the loss of most of the planet’s atmosphere, leaving Mars the bone-dry desert world that it is now. Since then, most astrobiologists have assumed that Earth-like planets in other solar systems would need a comparatively large moon to support complex life over long periods of time.
Given the generally accepted idea of how Earth got its big moon—through an improbable, dramatic collision with a Mars-sized body that knocked a huge chunk of Earth loose—astronomers estimate that only 1% of all Earth-like planets in the universe might actually have such a hefty companion. That would mean that planets harboring complex life might be relatively rare.
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Changes in the temps in the Arctic and Antarctic during the last 5 million years is not an appearance created by shifting land masses.
We know that, because land masses just haven't moved much during that time. The most significant developments over the last 30 million years have probably been uplifts/mountain range developments and maybe Central America region.
Here's a serious of maps from this site:
http://jan.ucc.nau.edu/~rcb7/global_history.html
60 million years ago the world looked quite different:
Compare that to the radical changes involved with the heating/cooling cycle's influence on ocean levels over the last 18 THOUSAND years:
much larger version here:
Look at the Gulf of Mexico
And now
There is some body of theory that states that relatively small geographical changes may have influenced the temperatures so that orbital variations (the primary explanation for the series of glacial and interglacial periods during the ice age) could cause ice expansion:
http://www.esd.ornl.gov/projects/qen/onset.html
http://www.sdnhm.org/archive/exhibits/mystery/fg_timeline.html
However that is somewhat guesswork. However, what is not guesswork is that the land masses we see now were very close to current positions 2 and 5 million years ago.
The previous interglacial (Eemian) was supposed to have been significantly warmer than it is now. Early Holocene (this interglacial) temps were warmer than they are now, at least in most of the north. However, recent studies of the Eemian have turned up strong evidence for some pretty cold periods during that interglacial itself, so we still don't understand a lot.
http://www.esd.ornl.gov/projects/qen/transit.html
http://en.wikipedia.org/wiki/Holocene_climatic_optimum
The northern part of the Greenland ice (Hans Tausen Iskappe) melted all the way away during the early Holocene, and since has reiced, apparently due to colder temps.
http://en.wikipedia.org/wiki/Hans_Tausen_Iskappe
The popular idea of stable temperatures for long periods seems to be less and less true the more research is done. Instead, redistributions of heat appear to produce pretty large variations in temps and moisture distribution even over rather short periods.
