Global Warming -- Why?

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Look to Mars for the truth on global warming

Snowball Earth

Commentator 1 wrote:

Following is a list of cycles that have been named after people:

Milankovitch 100,000 and 41,000 and 23,000 years (also perhaps 400,000 years)

Halstatt 2,300 years *

Gleissberg 80 to 90 years

Kondratieff 53 to 54 years

Brucker 36 years * (Commentator 2: you mean the E. Bruckner cycle of 35-36 years in temperature and rainfall. His work is about 120 years old.)

Hale 22 years

Kuznets 18 years

Juglar 9 years

Kitchin ~4 year (maybe a cluster of cycle lengths 3.39, 3.95, 4.45 years)

de Vries 207 years

Schwabe 11 years

* These two cycles are not commonly known by these names but there are references on www to them. ________________________________________________

Commentator 1 wrote:

Date: Fri May 12, 2006

Subject: climate periods match outer planetary periods

I have found a number of papers referencing this 2300 year cycle.

It even has a name - Hallstatt cycle!

This is another example of a solar period exactly matching planetary alignment periods. The 4 gas giants make good alignments with the sun every 2300 years on average. Global warming - at least the part due to the sun - is over and we can expect cooling for the next 1000 years or so. That is, provided the part due to humans gets under control. Of course, after that comes an ice age whether or not human get it under control.

Astronomy & Geophysics

Volume 44 Page 5.20 - October 2003

doi:10.1046/j.1468-4004.2003.44520.x

Volume 44 Issue 5

Solar cycle

Solar activity levels in 2100

Mark A Clilverd 1 , Ellen Clarke 2 , Henry Rishbeth 3 , Toby D G Clark 4 , Thomas Ulich 5 Mark A Clilverd, Ellen Clarke, Henry Rishbeth, Toby D G Clark and Thomas Ulich look forward to a little less solar activity in 2100, using direct and proxy records of past solar and geomagnetic activity.

Abstract:

We consider the likely levels of solar activity in 2100 by analysing the previous history of long-term solar and geomagnetic activity indices. We make use of superposed periods of similar variations in atmospheric cosmogenic radiocarbon that have occurred during the last 11 000 years, as derived from various proxies such as tree rings.

This leads us to conclude that solar activity is peaking at about the present epoch, and we expect solar activity in 2100 to resemble that in 1900 when a small minimum in solar activity took place, rather than increasing as has occurred in the last 100 years. The occurrence of major geomagnetic storms will decline to about one-third of the present level.

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Commentator 2 wrote:

Date: Fri May 12, 2006

Subject: climate periods match outer planetary periods

Commentator 1 wrote:

... Global warming - at least the part due to the sun - is over and we can expect cooling for the next 1000 years or so. ...

Commentator 2 wrote:

You mean the part influenced by the Milankovic cycles.

(OOPS! I said Milankovic, when these predictions were based on solar cycles, not orbital parameters. Still, there is an overall upward trend in solar output. Milankovic also predicts cooler sledding ahead. Perhaps in a century or so we'll wish we had more fossil fuels to burn.)

The Sun itself will continue to grow for the next 5 billion years. There is a new Red Spot on Jupiter, called "Red Junior," which seems to be due to increased insolation at that planet. Also, Mars is currently suffering an unprecedented rapid evaporation of the frozen poles. These changes suggest that the Sun's output is increasing. Whether that will be enough to offset the coming ice age is not clear.

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www.guardian.co.uk/science/story/0,,1920051,00.html

Earth's wobbly orbit blamed for mass mammal extinctions*

Ian Sample, science correspondent

Thursday October 12, 2006

The Guardian www.guardian.co.uk

Scientists have named a prime suspect in the mysterious case of the missing mammals. The reason history is littered with suspiciously regular extinctions is all down to the Earth's wobbly orbit, according to research published today.

Apart from mass extinctions caused by asteroids thumping into the planet and other cataclysmic natural events, records reveal that mammal species die out anyway, usually 2.5 million years after they first emerge. Archaeologists have struggled to explain it, with some blaming competition with neighbouring creatures and others suspecting dramatic swings in climate.

After examining the remains of 80,000 fossilised teeth from 132 different rodents that span a 22 million-year period, Jan van Dam at Utrecht University in the Netherlands believes he has the answer.

He conducted detailed analyses of the fossil fragments, which were excavated from four pristine sites throughout Spain, to work out when each species emerged and when they became extinct. The study, which focused on rodents because they are easily identified from their dental remains, included fossils of squirrels, mice, beavers, voles and hamster-like rodents, dating to between 24.5m and 2.5m years ago and only a few of which survive today.

Dr van Dam correlated the results with natural cycles in the Earth's orbit and found that every 2.4 million years there was a flurry of both mammal extinctions and new species.

The extinctions coincided with a cycle that sees the Earth's orbit vary from almost perfectly circular to elliptical. Another cycle of extinctions and emerging species overlapped with changes in the tilt of the Earth's axis, which occur every 1 million years. The axis today stands at 23 degrees to the vertical.

Writing in the journal Nature today, Dr van Dam says that when the Earth is in a very circular orbit the climate is less changeable, and summer heat will be less extreme. The more mild weather encourages glaciers to grow down from the poles, and causes a drop in ocean levels and changes to rainfall. "The ice expansion affects the global climate via atmospheric and oceanic currents," Dr van Dam said.

The climatic upheaval put pressure on mammals by wiping out food sources and fragmenting their habitats. For some species, the change in climate is enough to wipe them out, while others, by being forced to live in smaller, isolated communities, are likely to become new species, Dr van Dam claims. The evidence that the planet's wobbly orbit is to blame for mammals' 2.5 million-year s[ecies lifespan is "a crucial missing piece in the puzzle," said Dr van Dam.

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Antarctica

Commentator 2 wrote:

... The region at which they were looking has, indeed, gone through a remarkable recent warming trend, but this is mainly due to changing ocean currents. The global average and even the Antarctic average have not changed nearly so dramatically. Balloon measurements since 1971 show a 2.7 degree F winter temperature rise averaged over the continent. That is a much slower increase and about half the total that 60 minutes reported for the western peninsula, which is consistent with reports that other parts of the continent are actually getting colder.

Several studies over the last decade have shown that the thinning of the western Antarctic ice sheet has been proceeding at a very constant rate over the last 10,000 years. However, there are also spots elsewhere on the continent where the ice is actually getting thicker.

One important aspect of this polar warm up, is that it contradicts the predictions made by ALL the climate models that say anthropogenic greenhouse gases are to blame. These models have always predicted the region of maximum climate change to be at moderate latitudes in the near arctic regions but not near the poles. Most of the alarmists' flooding was supposed to come from expanding sea water as it warms, not from melting ice. The fact that we see such warming over the ice sheets suggests that there is some other cause for the warming.

The same models predict that the stratosphere should get colder as the troposphere gets warmer. However, until very recently, the stratosphere has either been warming or staying fixed. The recently slight cooling there does not come close to matching what the models predict, assuming that the recent rise in temperatures is due to the greenhouse effect.

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The spiral structure of the Milky Way, cosmic rays, and ice age epochs on Earth

by Nir J. Shaviv

Racah Institute of Physics, Hebrew University, Jerusalem 91904, Israel

The short term variability of the galactic cosmic ray flux (CRF) reaching Earth has been previously associated with variations in the global low altitude cloud cover.

This CRF variability arises from changes in the solar wind strength. However, cosmic ray variability also arises intrinsically from variable activity of and motion through the Milky Way.

Thus, if indeed the CRF climate connection is real, the increased CRF witnessed while crossing the spiral arms could be responsible for a larger global cloud cover and a reduced temperature, thereby facilitating the occurrences of ice ages.

This picture has been recently shown to be supported by various data [PhRvL 89 (2002) 051102]. In particular, the variable CRF recorded in Iron meteorites appears to vary synchronously with the appearance of ice ages ...

In addition, we show that apparent peaks in the star formation rate history, as deduced by several authors, coincides with particularly icy epochs, while the long period from 1 [billion] to 2 billion years before present, during which no glaciations are known to have occurred, coincides with a significant paucity in the past star formation rate.''

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www.sciencenews.org/articles/20070421/fob3.asp

by Davide Castelvecchi

``Northern Exposure: The inhospitable side of the galaxy?

The solar system's periodic visits to the northern side of the Milky Way expose life on Earth to extra cosmic rays that have caused catastrophic mass extinctions, two astrophysicists propose.

Biodiversity has had well-known ups and downs over the eons, with major extinctions followed by rebounds. In a 2005 study, Robert Rohde and Richard Muller of Lawrence Berkeley (Calif.) National Laboratory found that these swings were surprisingly regular, most of them taking place at intervals of about 62 million years. The researchers reached their conclusion after examining one of the most comprehensive long-term biodiversity surveys, a compilation of fossil data that charted the number of marine-life genera over the past 500 million years.

The extraordinary dinosaur kill 65 million years ago doesn't fit in the cyclic pattern, and experts widely blame it on the impact of a large asteroid.

To explain the cyclic pattern of mass extinctions, Rohde and Muller considered a phenomenon that has just about the right periodicity. As the solar system orbits around the galaxy, it swings from one side to the other of the galactic plane every 63 million years. Gravity from the rest of the galaxy's mass pulls the solar system back each time.

Perhaps when the sun is at the maximum distance from the galactic plane, Earth's biodiversity is at greatest risk, Rohde and Muller speculated. But that would put mass extinctions every 31.5 million years, not every 63 million. It wasn't clear why one side of the galaxy's plane would be more dangerous to life than the other.

Mikhail Medvedev and his colleagues of the University of Kansas in Lawrence now propose an explanation that rests on variations in the number of high-energy particles, known as cosmic rays, that strike Earth from space. They argue that because the galaxy is moving toward a large cluster of galaxies in the direction of the Virgo constellation, cosmic rays would be more abundant on the galaxy's north side, according to the view from Earth ...

When a cosmic ray hits the upper layers of the atmosphere, it triggers a shower of millions of energetic electrons and other particles, some of which can penetrate to land and into the oceans. The particles have a variety of effects. For example, they may alter cloud coverage or damage DNA, with potentially fatal consequences for entire species.

"Drops in biodiversity correspond to peaks in cosmic rays," Medvedev says. However, he and his colleagues stress that they haven't identified the mechanism linking cosmic rays and extinctions ...''

From Science News, Vol. 171, No. 16, April 21, 2007, p. 244.

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Commentator 3 wrote:

"The idea that a cosmic disaster may have caused global devastation some 1500 years ago is not entirely new. The conjecture was originally conceived in the early 1990s by Victor Clube and Commentator 3 Napier and later taken up and bolstered by Mike Baillie.The main evidence supportive of an environmental disaster around that time has been the discovery of narrow tree-rings in dendrochronological records found in numerous regions around the world. In fact, quite a number of 'narrow tree-ring events' has been detected that are dated to BC 4370, BC 3195, BC 2350, BC 1628, BC 1159, BC 207, BC 44 and AD 540. The sheer number of such narror tree-ring events suggests that we may be dealing with recurrent abrupt cooling events."

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1500 years ago something extreme happened to the world's climate-something that must have terrified those who witnessed it. The sun began to go dark. Rain poured red, as if tinted by blood. Clouds of dust enveloped the earth. Cold gripped the land for two years. Then came drought, famine, plague, death. Whole cities were wiped out - civilisations crumbled. There is evidence of a catastrophe - a catastrophe whose consequences affected the entire world-and may have changed the course of human history.

--David Keys, Catastrophe, PBS documentary 1999

Professor Hammer's team is testing a new Greenland core from the 530's AD that has just arrived at their laboratory. If pieces of a comet or asteroid had exploded in the atmosphere the team would expect to find traces of rare chemical elements like iridium.

If there had been a massive volcanic eruption, however, they would expect an excess of sulphuric acid - the telltale signature of a volcano. What will the ice reveal - cometary debris...or volcanic sulphates?

"What is important, I'll show you here it's the sulphuric acid and actually these huge amounts of sulphate here and lasting several years and clearly higher than anything else in this part of the record corresponds exactly to this around 535. So there's no doubt there is a major eruption."

--Catastrophe, PBS 2000

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(5) DAVID KEYS: EVIDENCE FOR THE VOLCANIC ORIGIN OF THE AD 535/36 DUST-VEIL EVENT

David Keys (1999) Catastrophe: An Investigation into the Origins of the Modern World. London: Century, pp. 270-272

"But there is another clinching piece of evidence which points away from a cosmic-impact explanation and towards a third option - a volcanic one. Buried up to 1,600 feet below the surface of the Greenland and Antarctic ice caps is a tell-tale layer of volcanic- originating sulphuric acid which was almost certainly associated with the 12-18-months- long sun-dimming event of 535/536 and the subsequent 'nuclear winter'-style climatic chaos ...

The final clinching evidence, however, comes from 10,0000 miles to the south - from deep inside the Antarctic ice cap. For 660 feet below the windswept surface, scientists, again using ice-cores, discovered evidence of a truly massive volcanic eruption. The ice-cores material revealed that acid snow had cascaded down on the Antarctic for at least four years running. From the Antarctic ice-cores at that time depth there are no accurate dates available - only rough, 50-year-long ranges of dates. All that can be said is that the four-year-long acid-snow episode recorded in the core occurred some time between 490 and 540.

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Sun's fickle heart may leave us cold

25 January 2007

From New Scientist Print Edition.

Stuart Clark

There's a dimmer switch inside the sun that causes its brightness to rise and fall on timescales of around 100,000 years - exactly the same period as between ice ages on Earth. So says a physicist who has created a computer model of our star's core.

Robert Ehrlich of George Mason University in Fairfax, Virginia, modelled the effect of temperature fluctuations in the sun's interior. According to the standard view, the temperature of the sun's core is held constant by the opposing pressures of gravity and nuclear fusion. However, Ehrlich believed that slight variations should be possible.

He took as his starting point the work of Attila Grandpierre of the Konkoly Observatory of the Hungarian Academy of Sciences. In 2005, Grandpierre and a collaborator, Gábor Ágoston, calculated that magnetic fields in the sun's core could produce small instabilities in the solar plasma. These instabilities would induce localised oscillations in temperature.

Ehrlich's model shows that whilst most of these oscillations cancel each other out, some reinforce one another and become long-lived temperature variations. The favoured frequencies allow the sun's core temperature to oscillate around its average temperature of 13.6 million kelvin in cycles lasting either 100,000 or 41,000 years. Ehrlich says that random interactions within the sun's magnetic field could flip the fluctuations from one cycle length to the other.

These two timescales are instantly recognisable to anyone familiar with Earth's ice ages: for the past million years, ice ages have occurred roughly every 100,000 years. Before that, they occurred roughly every 41,000 years.

Most scientists believe that the ice ages are the result of subtle changes in Earth's orbit, known as the Milankovitch cycles. One such cycle describes the way Earth's orbit gradually changes shape from a circle to a slight ellipse and back again roughly every 100,000 years. The theory says this alters the amount of solar radiation that Earth receives, triggering the ice ages. However, a persistent problem with this theory has been its inability to explain why the ice ages changed frequency a million years ago.

"In Milankovitch, there is certainly no good idea why the frequency should change from one to another," says Neil Edwards, a climatologist at the Open University in Milton Keynes, UK. Nor is the transition problem the only one the Milankovitch theory faces. Ehrlich and other critics claim that the temperature variations caused by Milankovitch cycles are simply not big enough to drive ice ages ..."

www.arxiv.org/astro-ph/0701117

Source: Issue 2588 of New Scientist magazine, 25 January 2007, page 12

environment.newscientist.com/article/mg19325884.500-suns-fickle-heart-may-leave-us-cold.html

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Commentator 2 wrote:

Milankovitch predicts 100 ky, 41 ky, and 23 ky. The short period one does not show up in isotope ratio proxies, because the north and south hemispheres are 180 degrees out of phase, canceling the global effects. The 41 ky amplitude is by far the strongest.

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Commentator 2 wrote:

The annual exchange rate of carbon between the air and land plants and soils is 121.6 gigatons of carbon per year; between air and oceans and other water bodies, 92 gigatons per year [212 gigatons total].

The total sink for CO2 in land and ocean is over 42,000 gigatons. The air currently holds about 750 gigatons of carbon. Our contribution from all industry and cement manufacturing ... is 5.5 gigatons per year.

The atmosphere accumulates less than 2 gigatons per year throughout the span of the industrial age, while we are now contributing 5.5 gigatons per year.

At 135,000 years ago, CO2 was higher than today. The lowest concentration was about 100 ppm at 45,000 years ago. (Barnola, 1987. Vostok ice core provides 160,000-year record of atmospheric CO2 Nature, 329, 408-414.)

Commentator 2 wrote:

The latest Mauna Loa reading is about 380 ...

You can see about 1 ppm per year directly from the Mauna Loa plot, which still translates to less than 2 gigatons per year. Notice that even the annual fluctuation in one hemisphere due to photosynthesis is larger than what "accumulates."

All this suggests that a small perturbation in any of the exchange processes contributing to the 212 gigatons coming and going could easily cause a buildup on this scale, instead of assuming it is due to the 5.5 gigatons addition to the stream. The Mauna Loa history suggests we could cut this in half and still have nearly the same accumulation each year.

Commentator 2 wrote:

Also, the rate of atmospheric CO2 increase was about the same 50 years ago, when our contribution was less than half what it is now. If the two were connected, you would certainly expect the rate of rise to increase, perhaps not double, but increase.

Commentator 1 wrote:

... The warming may preceed the CO2 by about 800 years I saw recently.

Commentator 2 wrote:

How is that possible, if CO2 is the driver? Everyone originally assumed it was just a problem with precision, that we simply couldn't measure the time proxies as precisely as the CO2 concentrations, but as precision (and accuracy) improved, the anomaly just becomes more pronounced. Temperature is driving CO2, not the other way around. Or, they mutually interact, but temperature is dominant through the Pleistocene.

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Commentator 1 wrote:

... The observation of other planets temperatures is unlikely to be contaminated with earth based effects I suppose. Are those measuremenst made from space or through the earth's atmosphere or both?

Commentator 2 wrote:

Both, and they agree.

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I just came across this for the first time, Commentator 1

Subject: 100,000-Year Climate Pattern Linked To Sun's Magnetic Cycles

Office of Public Affairs, Dartmouth College, Hanover, New Hampshire

June 6, 2002

100,000-YEAR CLIMATE PATTERN LINKED TO SUN'S MAGNETIC CYCLES, ACCORDING TO A NEW ANALYSIS

Thanks to new calculations by a Dartmouth geochemist, scientists are now looking at the earth's climate history in a new light.

Mukul Sharma, Assistant Professor of Earth Sciences at Dartmouth, examined existing sets of geophysical data and noticed something remarkable: the sun's magnetic activity is varying in 100,000-year cycles, a much longer time span than previously thought, and this solar activity, in turn, may likely cause the 100,000-year climate cycles on earth. This research helps scientists understand past climate trends and prepare for future ones.

Published in the June 10 issue of Earth and Planetary Science Letters (Elsevier, volume 199, issues 3-4), Sharma's study combined data on the varying production rates of beryllium 10 [Be-10], an isotope found on earth produced when high-energy galactic cosmic rays bombard our atmosphere, and data on the past variations in the earth's magnetic field intensity. With this information, Sharma calculated variations in solar magnetic activity going back 200,000 years, and he noticed a pattern.

Over the last 1 million years, the earth's climate record has revealed a 100,000-year cycle oscillating between relatively cold and warm conditions, and Sharma's data on the sun's magnetic activity corresponded to the earth's ice age history.

"Surprisingly, it looks like solar activity is varying in longer time spans than we realized," says Sharma. "We knew about the shorter cycles of solar activity, so maybe these are just little cycles within a larger cycle. Even more surprising is the fact that the glacial and interglacial periods on earth during the last 200,000 years appear to be strongly linked to solar activity."

Sharma's calculations suggest that when the sun is magnetically more active, the earth experiences a warmer climate, and vice versa, when the sun is magnetically less active, there is a glacial period. Right now, the earth is in an interglacial period (in between ice ages) that began about 11,000 years ago, and as expected, this is also a time when the estimated solar activity appears to be high.

Beryllium 10 is useful for studying the geology from hundreds of thousands of years ago mainly because it has a half-life of about one and a half million years. In addition, there are two key factors that have affected beryllium 10 production over the last 200,000 years: the earth's magnetic field and the sun's magnetic activity. When there are high-intensity solar magnetic storms, more charged particles are interacting with cosmic rays, and less beryllium 10 is produced. Likewise, the earth's magnetic field changes the flux of cosmic rays into and out of the atmosphere.

Since the production rate of beryllium 10 and earth's magnetic field intensity are known for the last 200,000 years, Sharma could calculate solar magnetic activity for this time period.

"I took sets of existing, independent data and made new comparisons and calculations," says Sharma. Then he went a step further to make a connection with the history of ice ages by looking at oxygen isotopes in the oceans, which reveal the history of how much ice was at the poles and are therefore a measure of average global surface temperature.

"I compared the estimated past variations in the solar activity with those of the oxygen isotopes in the ocean. Although there is a strong relationship between solar activity and oxygen isotopic variations, it is too early to say exactly what is the mechanism though which the sun is influencing the terrestrial climate."

One explanation of the 100,000-year cycle was offered by the Milankovitch Theory of Ice Ages in the 1940s, which suggested that the cyclical variations in the earth's orbit around the sun result in the earth receiving varying amounts of solar radiation that, in turn, control the climate. This explanation is under dispute because the variations of the solar energy in relation to the changes in orbit are very small. Other current research focuses on past variations in the sun's irradiance, or heat intensity (as opposed to the magnetic activity) ..."

www.dartmouth.edu/~news/releases/june02/climate.shtml

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Sun warming up explains global warming?

Posted by Commentator 2

Date: Thu Feb 8, 2007

Commentator 1 wrote:

Knowing that cosmic rays affect cloud making then any change in Be10 [beryllium-10] must be accompanied by cloud cover change.

Commentator 2 wrote:

Mostly true. The energy range overlap is not perfect. Be-10 is made by spallation reactions that require fairly energetic primaries. Clouds are enhanced by both energetic primaries and secondaries that reach the troposphere. In other words, a solar flare could make clouds without changing the Be-10 directly. Solar activity affects Be-10 indirectly by moving the Earth's magnetic field, which acts as a throttle for galactic cosmic rays.

Commentator 1 wrote:

Cloud cover change will affect heat reaching the earth's surface and therefore may alter the wind and other weather factors.

Commentator 2 wrote:

Mainly a net cooling effect is expected due to reflection of sunlight. However, clouds can also prevent cooling at night which can warm arctic winters.

Commentator 1 wrote:

Wind changes may affect the amount of material of different types being deposited on icecaps.

Commentator 2 wrote:

Since the Be-10 is made in the upper atmosphere, it gets pretty well distributed by the time it reaches the surface. It can take years to get there. It is not like volcanic dust that is distributed in a plume. Also, the ice core data is based on fairly large "bites" in time, so it reflects an average Be-10 deposit over long intervals. That is one of the frustrations in looking for a very brief pulse. Current ice core methods are not designed to notice.

C-14 calibrations follow similar curves, although this nuclide is made exclusively by secondary neutrons deep in the atmosphere, and it does not go back as far in time. The wiggles have been correlated with weather patterns in Europe using peat moss.

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Sun warming up explains global warming?

Posted by Commentator 2

Date: Thu Feb 8, 2007

Commentator 2 wrote:

Note that sunspots are missing during the Little Ice Age, and that they have been steadily increasing since, just like global temperatures.

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Anthropogenic

Posted by Commentator 2

Date: Tue Feb 20, 2007

Commentator 1 wrote:

... You cannot burn fossil fuels like humans are doing and not have any effect. That is absurd to suggest. ...

Commentator 2 wrote:

Here is one peer reviewed paper focused on cycles that indeed suggests it: Bard, E. and Frank, M. 2006. "Climate change and solar variability: What's new under the sun?" Earth and Planetary Science Letters 248: 1-14.

The authors review what is known, and unknown, about solar variability and its effects on earth's climate, focusing on the past few decades, the past few centuries, the entire Holocene, and orbital timescales.

Of greatest interest to cycle studies are Bard and Frank's conclusions about sub-orbital time scales, i.e., the first three of their four major focal points. Within this context, as they say in the concluding section of their review, "it appears that solar fluctuations were involved in causing widespread but limited climatic changes, such as the Little Ice Age (AD 1500-1800) that followed the Medieval Warm Period (AD 900-1400)."

Or as they say in the concluding sentence of their abstract, "the weight of evidence suggests that solar changes have contributed to small climate oscillations occurring on time scales of a few centuries, similar in type to the fluctuations classically described for the last millennium: The so-called Medieval Warm Period (AD 900-1400) followed on by the Little Ice Age (AD 1500-1800)."

In particular, they cite "Bond et al. (1997, 2001) followed by Hu et al. (2003) proposed that variations of solar activity are responsible for quasi-periodic climatic and oceanographic fluctuations that follow cycles of about one to two millennia."

As a result, as they continue, "the succession from the Medieval Warm Period to the Little Ice Age would thus represent the last [such] cycle," leading to the conclusion that "our present climate is in an ascending phase on its way to attaining a new warm optimum," due to some form of solar variability.

In addition, they note that "a recent modeling study suggests that an apparent 1500-year cycle could arise from the superimposed influence of the 90 and 210 year solar cycles on the climate system, which is characterized by both nonlinear dynamics and long time scale memory effects (Braun et al. 2005)."

Taken together, these observations leave little need to invoke the historical increase in anthropogenic CO2 emissions as the primary cause of modern warming. In fact, they leave no such need at all, as solar influences appear to be sufficient to explain the bulk of the increase in temperature ...

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Subject: Solar cycles & Global Warming

Commentator 4 wrote on 3-2-07:

Nice chart of "freezes" on Wiki, and it shows a ~200 year cycle. I get the shivers just thinking about the cosmic repercussions....

en.wikipedia.org/wiki/Image:Carbon14_with_activity_labels.svg

Then there is the 2,000-2,300 year Hallsatt cycle.

en.wikipedia.org/wiki/Principia_Discordia

The Schwabe solar cycle is not strictly 11 years long; it has been as short as 9 years and as long as 14 years in recent years. Nevertheless, statistical predictions of weather, based on these patterns can be made, subject to the additional factor of human activity.

The data suggests a gradual cooling during the next few centuries with intermittent minor warmups and a return to another "Little Ice Age" as early as 2100 although the best guess is two further cycles from that. There is weak evidence for a quasi-periodic variation in the sunspot cycle amplitudes with a period of about 90 years, suggesting a maximum sunspot occurs in three years 2010. I would guess two years later!

If we get through that crisis - not forgetting the importance of the year 2012 in the Maya Calendar, which by the way is NOT for a natural catastrophe, necessarily - it just marks the start of another long B'ak'tun cycle BUT surprisingly it jives with statistical analysis which suggests that we may well get a pole reversal on earth then - with unknown consequences ...

www.physorg.com/news65117758.html

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www.canada.com/nationalpost/story.html?id=edae9952-3c3e-47ba-913f-7359a5c7f723&k=0

Look to Mars for the truth on global warming

Lawrence Solomon, Financial Post

January 26, 2007

Climate change is a much, much bigger issue than the public, politicians, and even the most alarmed environmentalists realize. Global warming extends to Mars, where the polar ice cap is shrinking, where deep gullies in the landscape are now laid bare, and where the climate is the warmest it has been in decades or centuries.

"One explanation could be that Mars is just coming out of an ice age," NASA scientist William Feldman speculated after the agency's Mars Odyssey completed its first Martian year of data collection. "In some low-latitude areas, the ice has already dissipated." With each passing year more and more evidence arises of the dramatic changes occurring on the only planet on the solar system, apart from Earth, to give up its climate secrets.

NASA's findings in space come as no surprise to Dr. Habibullo Abdussamatov at Saint Petersburg's Pulkovo Astronomical Observatory. Pulkovo -- at the pinnacle of Russia's space-oriented scientific establishment -- is one of the world's best equipped observatories and has been since its founding in 1839. Heading Pulkovo's space research laboratory is Dr. Abdussamatov, one of the world's chief critics of the theory that man-made carbon dioxide emissions create a greenhouse effect, leading to global warming.

"Mars has global warming, but without a greenhouse and without the participation of Martians," he told me. "These parallel global warmings -- observed simultaneously on Mars and on Earth -- can only be a straightline consequence of the effect of the one same factor: a long-time change in solar irradiance."

The sun's increased irradiance over the last century, not C02 emissions, is responsible for the global warming we're seeing, says the celebrated scientist, and this solar irradiance also explains the great volume of C02 emissions.

"It is no secret that increased solar irradiance warms Earth's oceans, which then triggers the emission of large amounts of carbon dioxide into the atmosphere. So the common view that man's industrial activity is a deciding factor in global warming has emerged from a misinterpretation of cause and effect relations."

Dr. Abdussamatov goes further, debunking the very notion of a greenhouse effect. "Ascribing 'greenhouse' effect properties to the Earth's atmosphere is not scientifically substantiated," he maintains. "Heated greenhouse gases, which become lighter as a result of expansion, ascend to the atmosphere only to give the absorbed heat away."

The real news from Saint Petersburg -- demonstrated by cooling that is occurring on the upper layers of the world's oceans -- is that Earth has hit its temperature ceiling. Solar irradiance has begun to fall, ushering in a protracted cooling period beginning in 2012 to 2015. The depth of the decline in solar irradiance reaching Earth will occur around 2040, and "will inevitably lead to a deep freeze around 2055-60" lasting some 50 years, after which temperatures will go up again.

Because of the scientific significance of this period of global cooling that we're about to enter, the Russian and Ukrainian space agencies, under Dr. Abdussamatov's leadership, have launched a joint project to determine the time and extent of the global cooling at mid-century. The project, dubbed Astrometry and given priority space-experiment status on the Russian portion of the International Space Station, will marshal the resources of spacecraft manufacturer Energia, several Russian research and production centers, and the main observatory of Ukraine's Academy of Sciences. By late next year, scientific equipment will have been installed in a space-station module and by early 2009, Dr. Abdussamatov's space team will be conducting a regular survey of the sun.

With the data, the project will help mankind cope with a century of falling temperatures, during which we will enter a mini ice age ...

Habibullo Abdussamatov, born in Samarkand in Uzbekistan in 1940, graduated from Samarkand University in 1962 as a physicist and a mathematician. He earned his doctorate at Pulkovo Observatory and the University of Leningrad.

He is the head of the space research laboratory of the Russian Academies of Sciences' Pulkovo Observatory and of the International Space Station's Astrometry project, a long-term joint scientific research project of the Russian and Ukranian space agencies.

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news.nationalgeographic.com/news/2007/02/070228-mars-warming.html

Mars Melt Hints at Solar, Not Human, Cause for Warming, Scientist Says

Kate Ravilious

for National Geographic News

February 28, 2007

``Simultaneous warming on Earth and Mars suggests that our planet's recent climate changes have a natural -- and not a human-induced -- cause, according to one scientist's controversial theory.

Earth is currently experiencing rapid warming, which the vast majority of climate scientists says is due to humans pumping huge amounts of greenhouse gases into the atmosphere.

Mars, too, appears to be enjoying more mild and balmy temperatures.

In 2005 data from NASA's Mars Global Surveyor and Odyssey missions revealed that the carbon dioxide "ice caps" near Mars's south pole had been diminishing for three summers in a row ...''

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www.bbc.co.uk/science/horizon/2000/snowballearth.shtml

Snowball Earth

BBC2 9.00pm Thursday, 22nd February 2001

``There is a controversial theory that for millions of years the Earth was entirely smothered in ice, up to one kilometre thick. The temperature hovers around -40ºC everywhere, even in the tropics and the equator. If it did, then virtually nothing could survive this ferocious climate ...

For over fifty years a group of scientists has been trying to prove this incredible period of Earth history ...

Scientists across the world are starting to believe that in the past the Earth froze over completely for ten million years... then warmed up rapidly about 600 million years ago. Almost all life was wiped out. But out of the freeze emerged the first complex creatures on Earth ...

Telltale signs of past glaciation have been found in places that should have been much too hot - very near the equator. Even during the most severe ice age, scientists believed that the ice only reached as far down as Northern Europe and the middle of the USA. So what could these tropical deposits mean?

Back in the 1960s one of the first climate modellers, Mikhail Budyko, stumbled on an ingenious answer. Through some simple mathematical formulae, he calculated that if the polar ice caps had spread past a crucial point, a runaway freezing process would have followed, eventually freezing over the whole of the planet ...

The idea foundered because according to the model, once the Earth was frozen there was no way out - the Earth would remain frozen forever. The big freeze would wipe out all life; we would not exist today. It seemed patently absurd.

But then came a series of insights and inspirations from a geologist in California, Joe Kirschvink, who came up with a brilliant solution - that volcanoes, protruding above the frozen landscape, would have carried on pumping out carbon dioxide, the greenhouse gas, even though the world had entered the deep freeze.

On Snowball Earth there was no rain to wash this carbon dioxide out of the atmosphere. Instead it would have built up to higher and higher concentrations - until eventually it sparked off not just global warming but global meltdown.

From the baking landscape of Africa to ice-covered Antarctica, Horizon follows the tale of a theory which, if true, would have huge implications. Because scientists now believe this cycle of freezing and frying may have created the unique conditions needed for the evolution of complex life, including our own.''

-------------------

Transcript:

www.bbc.co.uk/science/horizon/2000/snowballearth_transcript.shtml

Snowball Earth

BBC2 9.00pm Thursday, 22nd February 2001

``NARRATOR (DILLY BARLOW): There is a theory that scientists once dismissed as absurd - that long ago the Earth became so cold every inch of it was entombed in ice. The whole planet became one vast snowball and it lasted for ten million years.

PROF. JOSEPH KIRSCHVINK (California Institute of Technology): The image of a frozen, white Earth was probably the worst nightmare I've personally ever come across. Death to an entire planet.

NARRATOR: For years the snowball theory has been dismissed as impossible. The critics said if the snowball had struck all life would have died and we would not exist ...

No one is certain what started them or why they happened, but there is one thing about ice ages on which most scientists agree. The conventional view is that no matter how ferocious the advance of the cold in any ice age there will always be parts of the world that are safe and warm. The freeze spreads out slowly from the poles, but never reaches the hottest part of the planet, the tropics.

It has long been assumed that this is a basic law of nature. The tropics can never freeze. But then this basic law of nature can't explain what happened 600 million years ago in Namibia. Paul Hoffman is one of those defiant geologists who disputes the conventional view. He has spent years trying to convince his colleagues about the snowball Earth.

PROF. PAUL HOFFMAN (Harvard University): As a scientist I was completely convinced it was right, but I knew I was going to have a struggle on my hands because any idea as radical as, as this is going to be difficult to get across and there are going to be sceptics for sure.

NARRATOR: The place Hoffman and his colleague, Dan Schrag, come back to study again and again is Namibia. It is not an obvious place in which to seek evidence of a catastrophic ice age. It is a land of relentless heat, one of those locations that has been in the ropics for hundreds of millions of years.

The conventional laws of nature say an ice age could never have penetrated here, but lurking among the sun-baked rocks is something that the conventional laws of nature cannot explain away. 600 million years ago these hills were at the bottom of the ocean and lying on the old seabed are mysterious boulders. Geologists call them drop stones and drop stones could only have been brought here by one thing: a glacier ... Because it has carved through the landscape a glacier always collects a huge amount of rock debris.

PROF. DANIEL SCHRAG (Harvard University): The ice would ... get filled up with all sorts of boulders and cobbles ... When most of the ice has melted is a point you can see that all the rocks the glacier's carried out to the ocean are now dropped to the sea floor. In addition to all of this, in the real world there'd also be a lot of sand and a lot of much finer grain sediment and so these rocks would get filled in with very fine grain sediment as well.

NARRATOR: In a few thousand years the fine grain sediment will cement itself together to form rocks, with the boulders trapped inside and that's how drop stones are made. All you need is a glacier. The message from the drop stones suggests just one thing: Namibia in the tropics, a place that everyone says has been hot for hundreds of millions of years, must once have been covered in ice.

PAUL HOFFMAN: The most compelling evidence here is the juxtaposition of a large boulder like this enclosed within very fine and delicately layered sediment and so it's difficult, if not impossible, to imagine any way to account for this other than a very extensive glaciation.

NARRATOR: But for 50 years, since the idea that an ice age must have smothered the tropics was first proposed, it has been deemed so radical that most scientists have dismissed it as absurd. The theory has its roots in the 1940s when a young geologist called Brian Harland made a series of intrepid field trips deep into the Arctic.

BRIAN HARLAND (Cambridge University): Conditions were very different then - manhauling [the sleds] in the old Scots tradition. It was cold but you get used to it, you can get used to anything really.

NARRATOR: In the Arctic Harland had ample opportunity to learn all there was to learn about that telltale sign of glaciation - drop stones.

BRIAN HARLAND: Glacial deposits were very dramatic, currents very distinctive, easy to identify and when I saw them I knew from my own experience that this is glacial. I didn't have to think very hard about it.

NARRATOR: But it was when he returned from the Arctic, armed with this new-found knowledge, that Harland made his scientific breakthrough. With his now expert eye, he analysed rocks from all over the world. What he discovered amazed him. Almost everywhere he looked, in rocks formed about 600 million years ago, he found drop stones: classic evidence that there had once been thick ice even on the hottest continents.

BRIAN HARLAND: There's no continent really without some glacial record. You have them in different parts of Europe, in Africa, plenty in Africa, not so well known in South America, but they have been known later in North America.

NARRATOR: The drop stones were so widespread that Harland began to contemplate the unthinkable.

BRIAN HARLAND: The fact is we've got evidence of a global glaciation.

NARRATOR: He knew it made no sense. He knew that at the peak of the last Ice Age, which ended just 10,000 years ago, ice spread down to where New York is today, but no further, but the evidence was staring Harland in the face, evidence which seemed to flout the laws of nature. 600 million years ago the drop stones said ice had spread over every continent, right across the tropics to the Equator itself.

It meant there must have been an ice age of unimaginable ferocity, in fact too unimaginable. When Harland presented his theory of global glaciation colleagues dismissed it as laughable.

BRIAN HARLAND: There was a lot of scepticism. I don't think I was ever shaken by it because I was pretty confident in my own observations, but I was interested and a bit annoyed in a way that, that so many people were hostile to the idea.

NARRATOR: The sceptics had a whole host of reasons why Harland had to be wrong, reasons that were utterly convincing, as they were based on the most basic rules about how the world works.

For a start, it's given that the tropics, that wide belt around the Earth, has always received the full glare of the sun. As they have always basked in sunlight, so they must always have remained warm. Even during the last Ice Age geological evidence suggests the tropics were pleasantly hot and they had another reason why the snowball theory must be wrong.

There was a far simpler explanation for drop stones in the tropics, one that was absolutely consistent with scientific knowledge and which didn't involve a ludicrous idea like the tropics freezing over. Continents drift. They scrape across the surface of the Earth at about the same pace that your fingernails grow. This means that in about 400 million years continents can shift from one end of the globe to the other.

Obviously, the doubters said, 600 million years ago all the continents had drifted into icy, polar regions. Once there, glaciers would have formed and drop stones would be common in all rocks of this era, and after those drop stones had been formed at the poles the land, and the drop stones, would have been carried back down to the tropics by continental drift.

For years this remained the accepted explanation for why drop stones appeared everywhere. The only way to make the theory of a global glaciation credible was for someone to make the impossible possible. They would need to find a way for the tropics to freeze over, and this is just what happened next.

(RUSSIAN COUNTDOWN) It was the 1960s, the height of the Cold War. The world was obsessed with calculating the odds of surviving a nuclear Holocaust. It was known that a series of massive nuclear explosions would create clouds of dust, smoke and soot. Sunlight would be blocked out. Hypothetically the Earth would enter a nuclear winter, a man-made ice age. In the Soviet Union finding out how severe this man-made ice age could be became the task for one climatologist. Mikhail Budyko was that man.

PROF. MIKHAIL BUDYKO (State Hydrological Institute, St. Petersburg): Long ago, probably 25 or 30 years, I compiled a number of studies which could be used to describe origin of ice ages.

NARRATOR: What Budyko was to uncover would fly in the face of conventional wisdom. He would show how those predictions that the tropics couldn't freeze over were complacent and unfounded.

Budyko knew that because the land and oceans are dark they absorb most of the heat coming from the Sun's rays and that is how our planet is warmed up; but sheets of ice are white. They reflect sunlight like a mirror, so an ice-covered Earth absorbs far less solar heat.

During an ice age as the freeze spreads the Earth grows whiter, more heat is reflected away so less and less heat is absorbed and so the Earth grows ever colder. It means that potentially the Earth could be caught in a vicious circle of unstoppable freezing.

Budyko converted this hypothetical scenario into a mathematical formula and that formula produced a terrifying prediction: the Earth's climate has a theoretical breaking point. As long as the ice sheets remain close to the poles the Earth is safe, but if the freeze continues, such as might happen in a nuclear winter, they could advance down to about where Texas is today.

Once the freeze had reached that point so much of the Earth would be covered in white ice that over half the solar heat that normally warms the planet would be reflected back into space. At that point there wouldn't be enough heat left to warm up the Earth.

Once this happens there could, in theory, be a runaway freeze, a freeze that nothing can stop. Temperatures plummet, ice sheets spread across all the continents, the oceans, and eventually even the tropics. If this was ever to happen the entire planet would be trapped in ice. There would be a snowball Earth.

What was most disturbing about Budyko's calculations was that an Earth encased in ice would reflect so much solar heat it could never warm up enough to thaw, ever. A snowball Earth would mean a world entombed in ice for eternity.

MIKHAIL BUDYKO: It was my opinion twenty years ago that such a system will be stable for very long time and possibly all life will disappear.

NARRATOR: This was Budyko's paradox. He had shown that a runaway freeze could ice over the tropics in theory, but he had also shown that it could never have happened in practice because, if it had, the world would still be a snowball today and that would mean we would never have existed.

For 15 years nobody could solve the paradox of the runaway freeze. The snowball Earth theory remained a logical impossibility. To resurrect the theory believers would have to do two things.

First, they had to prove that ice really had reached the hottest parts of the planet, the tropics, and that the drop stones hadn't arrived there merely through continental drift.

Second, they had to come up with a theory that offered an escape from the runaway freeze. That was when a new scientist entered the picture. In the late 70s Joe Kirschvink was one of geology's rising stars and back then he thought the idea of a snowball Earth was mad.

JOSEPH KIRSCHVINK: The willingness to accept a nutty idea like freezing the whole planet really needs to be supported by incredibly strong evidence and overall if you had asked me to place a wager back in the late 70s I would have been on the conservative side on that one.

NARRATOR: Kirschvink's conservatism came about because he believed the simple, conventional explanation for why there were drop stones at the Equator today. 600 million years ago, he thought, all the continents must have been up near the icy poles when the drop stones were formed. There was, however, only one technique for testing their theory and it just so happened that Kirschvink had dedicated his entire professional career to that technique. It involved magnets and Kirschvink is a man in love with magnets.

JOSEPH KIRSCHVINK: I have wiped out my credit cards so many times by playing with strong magnets I, I don't like to remember it.

NARRATOR: Few people realise it, but every rock is a weak magnet. Each one contains magnetic minerals and the direction these minerals pull in is fixed for ever the moment the rock is first formed and what gives these minerals their magnetic direction is the magnetic field round the Earth's core. This means that rocks formed at the poles will always have a magnetic direction that points up and down. Rocks formed at the Equator will always have a magnetic direction that points from side to side.

JOSEPH KIRSCHVINK: Rocks have the ability to preserve magnetic direction because of magnetic minerals in them. They act like little compass needles and will line themselves up.

NARRATOR: By finding out a rock's magnetic direction Kirschvink is able to identify where in the world it was originally formed, no matter where continental drift might have taken it in the millions of years that followed.

In the 1980s Kirschvink heard of a team of Australians who had run tests which, they claimed, showed evidence of glaciers in the tropics. Ever the sceptic, Kirschvink decided to duplicate their tests on his own, more sophisticated equipment. It meant examining drop stones from some of the hottest parts of the Earth. The question was: were they already at the Equator when they were formed by the ice, or had they been created at the poles and then carried to the tropics by continental drift? To answer the question Kirschvink turned to his pride and joy: a custom built, hypersensitive magnetometer.

JOSEPH KIRSCHVINK: It's, it's an incredible instrument. You lower the sample into the actual magnetometer chamber. The weak magnetic field of the sample generates an electric current and so it allows us to measure the magnetic moment of an extraordinarily weak magnet, one billionth, say, the level of an ordinary hand magnet I think.

NARRATOR: Attached to the magnetometer was a computer which plotted each rock's origin on an electronic outline of Earth as seen from above. The centre of the circle represented the poles, the circumference the Equator.

If the drop stones had been formed at the poles, as Kirschvink and everyone else thought, they would show up at the centre of the circle on the computer. If they had been formed at the Equator they would show up at the circle's edge.

The machine gave its answer: the drop stones had been formed in the tropics. 600 million years ago there must have been a snowball Earth. In the late 80s Kirschvink adopted the snowball Earth theory with fanaticism and if his findings flew in the face of existing theories about the laws of nature then stuff those theories.

JOSEPH KIRSCHVINK: There's a fundamental theorem in science: if the theory is in conflict with data modify the theory. There's so many wonderful, beautiful theories that have been slaughtered by a nasty little fact.

NARRATOR: But Kirschvink was racked by the insurmountable paradox of the runaway freeze, that if a snowball Earth had ever happened then science said we should still be entombed in ice today.

JOSEPH KIRSCHVINK: How do you get out of it? Obviously the climate modellers had assumed that that was an irreversible step and that you would never get out of it and yet we're out of it now and if we had been in it before some point we must have gotten out of it.

NARRATOR: To get out of the deep freeze what Kirschvink needed was a power that would stay hot, even when the whole planet had frozen over, something that Budyko hadn't thought of, something that could burn for ever, something like hell.

JOSEPH KIRSCHVINK: Looking at an active volcano you realise that magma tens or hundreds of kilometres below the surface couldn't care less whether there was a thin layer of ice over the oceans. It will still emerge.

NARRATOR: Volcanoes survive ice ages because they have a direct channel to the molten rock deep within the Earth, rock that reaches temperatures of over 1,000 degrees, but that would only melt ice in their immediate area.

Kirschvink had spotted something else about volcanoes: they also produce gas, ten billion tons a year. One gas volcanoes emit in huge quantities is carbon dioxide, a gas that causes the greenhouse effect and global warming.

Today carbon dioxide is being pumped into the atmosphere by both volcanoes and industrial activity, but what stops the Earth from overheating is that we have a natural way of removing the excess carbon dioxide from the atmosphere.

Rain is the Earth's natural cleaning agent. As it falls through the atmosphere each droplet of rain absorbs carbon dioxide and cleans the air, but Kirschvink realised that on a snowball Earth there could have been no rain. The snowball was so cold all the water on the planet's surface was frozen solid.

Without liquid water nothing could have evaporated into the air, so there would have been no clouds and without clouds there can be no rain and without rain, Kirschvink realised, there would have been nothing to cleanse the atmosphere of carbon dioxide.

JOSEPH KIRSCHVINK: You can't have rain if you don't have evaporation, so I couldn't see anything that would scrub out the carbon dioxide from the atmosphere under those conditions.

NARRATOR: It meant there would have been nothing to stop the carbon dioxide from the volcanoes from building up over millions of years. It would have caused global warming on an inconceivable scale. Kirschvink came across calculations showing that after ten million years without rain the atmosphere would have been 10% carbon dioxide. Today it is far less than 1%. This extra carbon dioxide would have created a greenhouse effect that raised the temperature to an average of 50 degrees Centigrade, hotter than the Earth has ever been, hot enough to melt the ice.

JOSEPH KIRSCHVINK: And that seemed to be a natural and possible escape, certainly enough to break the snowball, the ice condition.

NARRATOR: Joe Kirschvink had cracked it. He had found the way out of the runaway freeze, a way that made perfect scientific sense, a way that was consistent with the laws of nature.

JOSEPH KIRSCHVINK: The realisation that we may have found the way out of the snowball was wonderful.

NARRATOR: By 1990 Kirschvink had evidence that the tropics had frozen over for ten million years and he'd come up with a theoretical escape route from the runaway freeze, but the problem was it was just a theory. He had no physical evidence to prove the ice had melted because of an extreme greenhouse effect and without that evidence the snowball Earth theory continued to be ignored. But all that was about to change. In 1992 Paul Hoffman entered the story. One of geology's most respected, but open-minded figures, he was to turn into one of the snowball Earth theory's most fervent disciples.

PAUL HOFFMAN: I love the snowball Earth theory. I mean it's almost a religious ferocity with which I want to get across this, this saga of Earth history with so many twists and turns and, and events that, that are, are, are so far outside the, our own experience.

NARRATOR: Hoffman's mission was to find that hard evidence that had alluded Kirschvink, the final piece of the puzzle that would prove the snowball had ended because of the greenhouse effect and he knew just where to start looking: Namibia. Hoffman was drawn to Namibia first by the drop stones, but even more by what sat immediately on top of them. Towering directly above were huge formations called cap carbonates, calcium carbonate crystallised into rock. These bizarre structures seemed to appear right out of the blue.

PAUL HOFFMAN: Above this line right here... creates... on top no more stones whatsoever, so the glaciation must have come to an abrupt end and sitting directly on top is a thick pile of carbonate and it's puzzled geologists for generations.

NARRATOR: What really puzzled geologists was that caps made from calcium carbonate are usually formed in warm water, but in Namibia they had suddenly appeared on top of an ice-cold glacier.

PAUL HOFFMAN: What this indicates is that you go from glacial conditions to an ocean that is warm in a flash.

NARRATOR: To most geologists this instant change from cold to hot rock defied their understanding, but Hoffman suspected it might be a huge clue, that the sudden appearance of mountains of calcium carbonate must somehow be linked to the death of the snowball in a colossal greenhouse effect, but how? Hoffman needed someone who could explain why calcium carbonate would be formed not just because of warm conditions in general, but specifically in the conditions created by a melting snowball Earth, so he turned to a geochemist, Dan Schrag.

PAUL HOFFMAN: I talked about this problem with a number of people but the one person who grabbed this problem with both hands right from the outset was my colleague, Dan Schrag.

NARRATOR: Painstakingly they analysed the snowball's theoretical final moments stage by stage, working out what chemical and climatic processes were at work. First they realised that as the ice melted it would produce liquid water. The water would then evaporate and create clouds and those clouds would cause a change in the weather the likes of which has never been seen by human eyes.

DANIEL SCHRAG: When the ice is retreating this is probably the most spectacular climate change in our history. In some ways we're going from the coldest climate the Earth's ever experienced to the warmest climate the Earth's ever experienced. We immediately said that this was the mother of our climate changes.

NARRATOR: The most elemental powers of nature would be unleashed upon the Earth.

PAUL HOFFMAN: One would predict hurricanes of such intensity that our unimaginable, so it's quite possibly you could have had waves of, you know, 100 metres in, in, in amplitude coming in and crashing in on the shoreline, so it would just be unbelievably violent.

NARRATOR: And above all there would be rain, the first rain storms for millions of years, rainstorms that would last at least a century and it wouldn't be just any rain. The rainwater would react with the vast quantities of carbon dioxide in the atmosphere and form carbonic acid. This acid rain would then deluge the Earth.

The acid rain would pound the exposed rocks, producing a violent chemical reaction. It would break the rocks down into their consistuent parts, one of which was calcium. This would then fuse with the carbon in the acid rain. The result: mountains of calcium carbonate exactly as they could see right above the drop stones in Namibia.

DANIEL SCHRAG: Suddenly it became clear that the natural expectation of a prolonged global glaciation ending in extremely high levels of carbon dioxide was that you would expect these very unusual thick carbonate rocks should immediately follow the glacial deposits.

NARRATOR: Hoffman and Schrag had found the final evidence.

PAUL HOFFMAN: The beauty of the snowball Earth theory is exactly that it links the chemistry, the geology, the planetary science and bam-bam-bam, all of the facts are, are consistent with the predictions of the theory.

NARRATOR: In 1998 Hoffman and Schrag made a triumphal tour of the world's universities promoting the snowball theory, and then someone threw a spanner in the works. An entire scientific discipline, the biologists, took one look at the ten million year long snowball Earth and said it was quite simply impossible.

One scientist who had problems with the snowball was Guy Narbonne. He, like many other biologists, could see there was a fundamental problem reconciling the snowball Earth theory with what he knew.

PROF. GUY NARBONNE (Queen's University, Kingston, Ontario): The geological evidence speaks very strongly of ice sheets marching on the Equator. The biological evidence speaks very strongly of open water being available at this whole time.

NARRATOR: Narbonne's problem was another set of nature's laws, nothing less than the laws that govern life itself. 600 million years ago, when the snowball was said to have struck, there was nothing living on the land. It all existed in the sea, and it was not life as we know it. The most common organism on the planet was this: cyano-bacteria. This mass of fossilised cyano-bacteria is so ancient it predates even the snowball.

[Would the world freeze have wiped out higher forms of life that might have existed even a billion years ago?]

GUY NARBONNE The oldest fossils that we have in the world are stromatalytes and these are colonies like you see here and they're made out of literally billions of cyano-bacteria.

NARRATOR: What made cyano-bacteria and more sophisticated ancient organisms like green algae central to the snowball debate was that they photosynthesised. Just like plants today under the water these life forms absorbed sunlight and converted it into energy, so these species' chances of surviving the snowball would have depended on whether there was enough sunlight for photosynthesis in the snowball seas at a time when every inch of the planet was allegedly covered in thick ice.

GUY NARBONNE: Light penetration through ice is not great if the ice is more than a couple of tens of metres thick.

NARRATOR: And that was the problem biologists pointed to in Hoffman and Schrag's work. Their calculations had reckoned on the snowball producing ice sheets up to a kilometre thick and even in the warmest places around the Equator they would have been tens of metres thick, more than enough, biologists believe, to block out any sunlight from the oceans and that meant death to most things that depended on photosynthesis for life.

GUY NARBONNE: You cut off photosynthesis and within a few years, let alone a few million years, mass extinction.

NARRATOR: It meant that many of the photosynthesising species should have become extinct 600 million years ago and the trouble was they hadn't. Cyano-bacteria grow in rock-like colonies all over the tropics today, as do other photosynthetic plants dating from before the snowball like green algae.

For many biologists there seemed to be only one possible conclusion: there may have been a severe ice age, but not a fully fledged snowball that covered all the oceans because life forms that should have died out are still with us. Unless someone could find a way for marine life to survive under a thick sheet of ice the whole theory would be back in the bin. Then along came the man from NASA, Chris McKay.

DR. CHRIS McKAY (Space Science Division, NASA): I'm a planetary scientist with an interest in life in extreme environments, in particular environments that are cold and dry. Several years ago I saw the papers about the snowball Earth indicating the geological evidence that the Earth was ice-covered and had been ice-covered for millions of years, plus the evidence that there were organisms, bacteria and green algae, that survived this ice-covered state and that's the puzzle: how could these photosynthetic organisms survive?

NARRATOR: McKay was intrigued because it just so happened he had visited a place on Earth today that was so cold it could actually be compared with the snowball of 600 million years ago: Antarctica, the coldest place on Earth. Here temperatures can fall to -30%ordm;C, almost as severe as the snowball at its warmest point (the Equator) and deep in Antarctica are the dry valleys where there are lakes smothered by an ice sheet many metres thick.

CHRIS McKAY: We think these little lakes represent a good model for looking at the snowball Earth - could there by life underneath the ice cover on a snowball Earth?

NARRATOR: Scientists were eager to discover if there was enough light for life to survive in the water below the thick ice. They were about to be astonished. There was light, lots of it, even though overhead the ice was five metres thick. There was so much light the water was filled with plant life and bacteria including two organisms dating from the time of the snowball that would have needed sunlight to live.

CHRIS McKAY: When we're diving in the lakes and swimming around there's life in the water, there's bacteria, cyano-bacteria, but there's also green algae.

NARRATOR: And McKay had a hunch as to why this photosynthetic life could survive. It was something about the nature of the ice itself. It was like glass. It didn't block out sunlight at all.

CHRIS McKAY: The transparency of this ice is very high and it's due to the fact that it's freezing very slowly underneath this thick ice cover. Now let's imagine the snowball Earth where there's also a thick ice cover. The ice on the bottom is freezing very slowly as well, yet you have the same optical properties as this clear, clean ice.

NARRATOR: By freezing slowly, water rejects impurities such as salt or dirt which make it cloudy, so the ice becomes clean and transparent. Because of this transparency life-giving sunlight would have been reaching down into the snowball seas.

McKay realised that even at its height there would have been havens around the snowball's Equator where the ice was thin enough for photosynthetic life to cling on below.

But there was more. Although disciples of the theory accept the snowball would have been death to most things, they argue whatever life did survive would have emerged into a new world almost devoid of competition, the perfect conditions for an explosion of evolutionary change.

These fossils show the new species which appeared soon after the time of the snowball. All display a massive increase in size and complexity from the simple organisms that lived before. These are the first multi-cellular life forms. Even those with some questions about the snowball theory recognise a new climate after a mass extinction could be a spur for evolution.

GUY NARBONNE: All we can say for sure is that the complexity of life dramatically increases after the snowball glaciations. What we can infer is that the greatest environmental catastrophe to ever strike the Earth is probably in some way related to the greatest evolutionary explosions that have ever characterised the Earth.

NARRATOR: It may just be that the snowball saga was the biggest force for the development of life the world has ever seen. But if the snowball can change the course of life on the planet there remains one final question. No one knows why the snowball happened or if it could happen again.

The sun is hotter than it was 600 million years ago and is getting hotter all the time ... If it ever did happen again it ... would mean death to almost everything, including us.''

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