Going to Earth's core for climate insights

Mar 10, 2011
A NASA/university study of data on Earth's rotation, movements in Earth's molten core and global surface air temperatures has uncovered interesting correlations. Credit: NASA/JPL-Université Paris Diderot - Institut de Physique du Globe de Paris

(PhysOrg.com) -- The latest evidence of the dominant role humans play in changing Earth's climate comes not from observations of Earth's ocean, atmosphere or land surface, but from deep within its molten core.

Scientists have long known that the length of an day - the time it takes for Earth to make one full rotation - fluctuates around a 24-hour average. Over the course of a year, the length of a day varies by about 1 millisecond, getting longer in the winter and shorter in the summer. These seasonal changes in Earth's length of day are driven by exchanges of energy between the solid Earth and fluid motions of Earth's atmosphere (blowing winds and changes in ) and its ocean. Scientists can measure these small changes in Earth's rotation using and very precise geodetic techniques.

But the length of an Earth day also fluctuates over much longer timescales, such as interannual (two to 10 years), decadal (approximately 10 years), or those lasting multiple decades or even longer. A dominant longer timescale mode that ranges from 65 to 80 years was observed to change the length of day by approximately 4 milliseconds at the beginning of the 20th century.

These longer fluctuations are too large to be explained by the motions of Earth's atmosphere and ocean. Instead, they're due to the flow of within Earth's outer core, where Earth's magnetic field originates. This fluid interacts with Earth's mantle to affect Earth's rotation. While scientists cannot observe these flows directly, they can deduce their movements by observing Earth's magnetic field at the surface. Previous studies have shown that this flow of liquid iron in Earth's oscillates, in waves of motion that last for decades with timescales that correspond closely to long-duration variations in Earth's length of day.

Still other studies have observed a link between the long-duration variations in Earth's length of day and fluctuations of up to 0.2 degrees Celsius (0.4 degree Fahrenheit) in Earth's long-term global average surface air .

So how might all three of these variables - Earth's rotation, movements in Earth's core (formally known as the core angular momentum) and global surface air temperature - be related? That's what researchers Jean Dickey and Steven Marcus of NASA's Jet Propulsion Laboratory, Pasadena, Calif., and colleague Olivier de Viron of the Universite Paris Diderot and Institut de Physique du Globe de Paris in France, set out to discover in a first-of-its-kind study.

The scientists mapped existing data from a model of fluid movements within Earth's core and data on yearly averaged length-of-day observations against two time series of observed annual global average surface temperature: one from NASA's Goddard Institute of Space Studies in New York that extends back to 1880, and another from the United Kingdom's Met Office that extends back to 1860. Since total air temperature is composed of two components - temperature changes that occur naturally and those caused by human activities - the researchers used results from computer climate models of Earth's atmosphere and ocean to account for temperature changes due to human activities. These human-produced temperature changes were then subtracted from the total observed temperature records to generate corrected temperature records.

Time series of Earth's surface air temperature (black line) and time series corrected for the influence of human activities (red line), Earth's length of day (green line) and Earth's core angular momentum (blue line). Credit: NASA/JPL-Université Paris Diderot - Institut de Physique du Globe de Paris

The researchers found that the uncorrected temperature data correlated strongly with data on movements of Earth's core and Earth's length of day until about 1930. They then began to diverge substantially: that is, global surface air temperatures continued to increase, but without corresponding changes in Earth's length of day or movements of Earth's core. This divergence corresponds with a well-documented, robust global warming trend that has been widely attributed to increased levels of human-produced greenhouse gases.

But an examination of the corrected temperature record yielded a different result: the corrected temperature record remained strongly correlated with both Earth's length of day and movements of Earth's core throughout the entire temperature data series. The researchers performed robust tests to confirm the statistical significance of their results.

"Our research demonstrates that, for the past 160 years, decadal and longer-period changes in atmospheric temperature correspond to changes in Earth's length of day if we remove the very significant effect of atmospheric warming attributed to the buildup of greenhouse gases due to mankind's enterprise," said Dickey. "Our study implies that human influences on climate during the past 80 years mask the natural balance that exists among Earth's rotation, the core angular momentum and the temperature at Earth's surface."

So what mechanism is driving these correlations? Dickey said scientists aren't sure yet, but she offered some hypotheses.

Since scientists know air temperature can't affect movements of Earth's core or Earth's length of day to the extent observed, one possibility is the movements of Earth's core might disturb Earth's magnetic shielding of charged-particle (i.e., cosmic ray) fluxes that have been hypothesized to affect the formation of clouds. This could affect how much of the sun's energy is reflected back to space and how much is absorbed by our planet. Other possibilities are that some other core process could be having a more indirect effect on climate, or that an external (e.g. solar) process affects the core and climate simultaneously.

Regardless of the eventual connections to be established between the solid Earth and climate, Dickey said the solid Earth's impacts on climate are still dwarfed by the much larger effects of human-produced greenhouse gases. "The solid Earth plays a role, but the ultimate solution to addressing climate change remains in our hands," she concluded.

Explore further: Suomi NPP satellite spots birth of Tropical Cyclone Kate

More information: Study results were published recently in the Journal of Climate.

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User comments : 19

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technicalengeneering
5 / 5 (4) Mar 10, 2011
facinating
thermodynamics
5 / 5 (5) Mar 10, 2011
This is an amazing piece of work. It is worthy of other teams attacking to attempt to falsify the work because it is such an important hint at the workings of the Earth. This team had to come up with the concept then do the numerical work to verify the correlation. The intellectual effort involved is astonishing. Again, it is worthy of a significant effort at reproducing or falsifying because of the remarkable correlation between the core and the natural variation in temperature. I will be watching closely for more work in this area.
Question
1.8 / 5 (8) Mar 10, 2011
quote from article: "Scientists have long known that the length of an Earth day - the time it takes for Earth to make one full rotation - fluctuates around a 24-hour average. Over the course of a year, the length of a day varies by about 1 millisecond, getting longer in the winter and shorter in the summer."

Could this be due to the fact that the earth is closer to the sun during the northern winter? Time runs slower in a stronger gravity field.
barakn
3.8 / 5 (10) Mar 10, 2011
@Question - No. Clocks in the stronger gravity field would also run slower, completely masking the "slowing" of the rotation. Plus the actual gravitational time slowdown would be much smaller than a millisecond.
astro_optics
1.7 / 5 (6) Mar 10, 2011
Once again, the curves are correlated, but out of phase...could this be read as humans are having the effect on earth's rotation as well??? We are the mighty humans!!!
astro_optics
2.3 / 5 (6) Mar 10, 2011
The reduced tidal forces due to the increased distance from the sun should have an effect!
Question
1 / 5 (1) Mar 10, 2011
Barakn: Can you make a direct comparison between a change in gravitational time in a large rotating object like the earth and an atomic clock? For example, if the earth were 16,000 miles in diameter would the change in the rotational surface velocity equal the change in the surface velocity of an earth with an 8,000 mile diameter one?
omatumr
1.4 / 5 (18) Mar 10, 2011
The bold black line in the graph of Earth's surface air temperatures looks remarkably like the one discredited by a recent study at UC-Berkeley. See the video in

anhonestclimatedebate.wordpress.com/2011/03/10/hide-the-decline-explained/

The root of the problem seems to be in Washington, DC where the US National Academy of Sciences reviews budgets of research agencies for Congress and allocates funds to organizations that report evidence for "CO2-induced global warming" in exchange for government funds, as former President Eisenhower warned might happen on day in his 1961 farewell address:

youtube.com/watch?v=GOLld5PR4ts

With kind regards,
Oliver K. Manuel
Skeptic_Heretic
5 / 5 (6) Mar 11, 2011
Barakn: Can you make a direct comparison between a change in gravitational time in a large rotating object like the earth and an atomic clock? For example, if the earth were 16,000 miles in diameter would the change in the rotational surface velocity equal the change in the surface velocity of an earth with an 8,000 mile diameter one?

Question, that's unnecessary. There is no objective measure of time. If you are a clock counting time and time slows down, you slow down too. Regardless of how accurate you are, you will not notice the change in the flow of time because you are a party to that change and not an objective referential observer.
GSwift7
1 / 5 (1) Mar 11, 2011
what about the most recent 15 years of data on CAM and the past 5-7 years of data on everything else? Why did they stop at around 2005?
GSwift7
3.4 / 5 (5) Mar 11, 2011
Question, that's unnecessary. There is no objective measure of time. If you are a clock counting time and time slows down, you slow down too. Regardless of how accurate you are, you will not notice the change in the flow of time because you are a party to that change and not an objective referential observer


The LoD measurements are made relative to astronomical observations, so a change in the local flow of time must be accounted for if it is significant. I have read that the GPS navigation system would not function well if local deviations in the flow of time were not continuously accounted for.
Question
1 / 5 (1) Mar 11, 2011
Thanks for the information GSwift7, that sheds some light on it. So the 1 millisecond difference between the summer and winter could be caused by the difference in the sun's gravitational field. But that creates another question, how would the earth's angular momentum be conserved?
Skeptic_Heretic
5 / 5 (2) Mar 11, 2011
Question, that's unnecessary. There is no objective measure of time. If you are a clock counting time and time slows down, you slow down too. Regardless of how accurate you are, you will not notice the change in the flow of time because you are a party to that change and not an objective referential observer


The LoD measurements are made relative to astronomical observations, so a change in the local flow of time must be accounted for if it is significant. I have read that the GPS navigation system would not function well if local deviations in the flow of time were not continuously accounted for.

Yes and that isn't due purely to gravity, that also has to do with referential frame and speed. The faster you go, the slower time passes for your reference frame.
Nik_2213
not rated yet Mar 11, 2011
"There is no objective measure of time."
IIRC, observations of fast pulsars situated orthogonally may be used to correct for gravitational effects...
Howhot
3.4 / 5 (5) Mar 12, 2011
So we finally have, after years of study, identified the source of global warming. The molten hot center of the earth some how effects pulsar bogons situated orthogonally to the rotational axis of earth;s magnetic field, to channel the bogonatious forces toward the center, heating the atomosphere as the descend.
(Just kidding guys).
GSwift7
3 / 5 (2) Mar 14, 2011
Yes and that isn't due purely to gravity, that also has to do with referential frame and speed. The faster you go, the slower time passes for your reference frame


yes, exactly. For instance, the GPS satellites on the sunward side of the earth compared to the ones farthest from the sun at any given time have a significant difference in relative velocity, since one is moving against the earth's orbit and the other is moving in the same direction as the earth. When you're talking about miliseconds or small dopler effect changes, it's a significant effect. According to a book I read once, if you tried to fly to the moon and you didn't account for the change in the rate of the flow of time due to leaving Earth's gravity well, you would miss the moon. I don't remember what book that was though. Maybe A Brief History of Time? I don't know. Question, if you haven't read that one, you might enjoy it. It's a little outdated but still good.
nickelsworth
1 / 5 (4) Mar 14, 2011
The science of Earth Oceanography is still very much in its infancy. To actually understand what is going on only six miles beneath sea level is extremely difficult... let alone the earth's [and/or sun's core]. What is the last element that solar fusion cannot consume? What is the predominant element of earth's core? The cores of both earth and sun are directly tied into one another! Is there anyone out there that can come up with any kind of symbolic logic to this? I have no pedigree. That said, an old saying comes to mind; 'We are not as fart as we stink we am'. P.S. The black line shows a distinct 'head and shoulders' signature between the mid 1950's and the mid 1960's. Stock markets will show this same signature before they quickly bolt upwards, peak, and crash steeply downward. Dress warm. Buy snowshoes.
Ethelred
5 / 5 (6) Mar 15, 2011
What is the last element that solar fusion cannot consume?
Iron.

What is the predominant element of earth's core?
Iron, wait for it.

The cores of both earth and sun are directly tied into one another!
Where did that come from? The Sun's core is hydrogen and helium. And there is rather a lot more of each between the Sun's core and the surface and another 93 million miles between the Sun and the Earth.

Is there anyone out there that can come up with any kind of symbolic logic to this?
Yes. Core A is not equal to Core b.

Did your post have a purpose? If so what was it?

The black line shows a distinct 'head and shoulders' signature between the mid 1950's and the mid 1960's.
And then continues on up. And it ISN'T a head and shoulders. If you MUST misuse a stock market analogy its series of rising tops and bottoms and YOU are not ever going to be my Stock Market Elf if you can't tell Tops and Bottoms from Head and Shoulders.

Ethelred
yyz
4.4 / 5 (7) Mar 15, 2011
"The cores of both earth and sun are directly tied into one another! Is there anyone out there that can come up with any kind of symbolic logic to this?"

This sounds like a job for Plasma Cosmology and-or Neutron Repulsion. They're both light years ahead of current theory(pun intended). :^)

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