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Science

Sun's Activity Levels Reconstructed 38

Posted by michael from the invest-in-tanning-salons dept.
neutron_p writes "An international team of scientists has reconstructed the Sun's activity over the last 11 millennia and forecasts decreased activity within a few decades. The activity of the Sun over the last 11,400 years, i.e., back to the end of the last ice age on Earth, has now for the first time been reconstructed quantitatively. The scientists have analyzed the radioactive isotopes in trees that lived thousands of years ago. As scientists report in the current issue of the science journal Nature, one needs to go back over 8,000 years in order to find a time when the Sun was, on average, as active as in the last 60 years."
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Sun's Activity Levels Reconstructed More

Sun's Activity Levels Reconstructed

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  • this isn't, co-incidentally, the same amount of time we've been traking a growing hole in the ozone layer over Antarctica, is it?

  • In other news... (Score:5, Funny)

    by k4_pacific ( 736911 ) <`moc.oohay' `ta' `cificap_4k'> on Thursday October 28, 2004 @02:43PM (#10656280) Homepage Journal
    In order to investigate the issue, NASA has announced that they are sending an unmanned space probe to the sun. In order to avoid the intense heat, they are planning on launching the probe at night.
    • I believe the now-cancelled Solar Probe mission was to have flown at night, for the same reason you posted. IIRC, some portion of its trajectory was to have placed it in the shadow of a sun-grazing asteroid...local night. This would have a) kept its electronics cool until it was ready to begin its final mission, and b) given us a chance to study the asteroid at close range.

      Since the mission was cancelled, the NASA "Fire and Ice" page (combining this mission and the Pluto-Kupier Belt probe has been taken
    • In order to avoid the intense heat, they are planning on launching the probe at night.

      What a typical NASA screwup!

      They obviously confused a landing requirement with a launch requirement.

      -

  • Error Bars (Score:5, Interesting)

    by CheshireCatCO ( 185193 ) on Thursday October 28, 2004 @02:50PM (#10656337) Homepage
    I'm not sure I trust their error bars (they appear on the second plot). Since they're using 10-year averages, they should be removing the effects of the solar cycle. But their sunspot number curves drop below 0 sunspots in several places. A negative number of sunspots is, obviously, unphysical. Also, their data is pretty wildly varying over short timescales (again, solar cycle should be removed) and doesn't match the actual sunspot records from 1610 on very well, either.
    • A negative number of sunspots is, obviously, unphysical.

      Are you sure you don't mean unpossible [simpsoncrazy.com] ?

    • Re:Error Bars (Score:4, Informative)

      by Idarubicin ( 579475 ) on Thursday October 28, 2004 @04:45PM (#10657470) Journal
      m not sure I trust their error bars (they appear on the second plot). Since they're using 10-year averages, they should be removing the effects of the solar cycle. But their sunspot number curves drop below 0 sunspots in several places. A negative number of sunspots is, obviously, unphysical. Also, their data is pretty wildly varying over short timescales (again, solar cycle should be removed) and doesn't match the actual sunspot records from 1610 on very well, either.

      Unfortunately, most people don't have online access to Nature for the full text of the original article. (For those who do, it's here [nature.com]. If you actually check the data--they have a plot of just the last thousand years comparing various methods--the match with the records from 1610 on is actually quite good.

      They also comment that, "The slightly negative values of the reconstructed SN [sunspot number] during the grand minima are an artefact; they are compatible with SN = 0 within the uncertainty of these reconstructions as indicated by the error bars." I'm not surprised that their calibration might be a bit off when they've had to extrapolate sunspot numbers lower or higher than we've seen with firm data in the last four hundred years.

      • What bothered me about the negative values is that in a one or two places the curve drops about an error bar below 0. While within the error bar, that's still kind of scary. And since the sunspot number is at least *claimed* to have gotten down that far in the past 400 years (during the Maunder Minimum), they should be able to extrapolate assuming a robust algorithm.

        One meta-reason that I was (and am) so skeptical of the error bars is how dicey their extrapolation seems. They're using C-14 as a proxy fo
    • Sun is known to be a variable star. In many variable stars, there are more than one cycles happening, mainly harmonically related. Sun spot cycle which is 9-11 years long also cycles in longer periods. I wouldn't be suprised to read there also exists a 8 thousand year cycle.

  • What? (Score:2, Funny)

    by DHalcyon ( 804389 )
    They've been around for so long and their Java-Interpreter is still not... Oh, wait, you mean that other sun, don't you?

  • Sun activity and climate (Score:4, Interesting)

    by StarWynd ( 751816 ) on Thursday October 28, 2004 @02:54PM (#10656375)
    One thing I'm curious about is what effect that the Sun's activity has on climate change. There have been spacecraft [nasa.gov] studying the sun and more spacecraft [swri.edu] studying the magnetosphere and it's interaction with the solar wind. However, it seems that we only have understanding of individual events and the immediate effects of those events. It will be really interesting when some people get a good idea of what long term effects CMEs (coronal mass ejections) and other Sun activity has on our little blue world.

  • Solar Weather Forecast Accuracy (Score:3, Interesting)

    by VernonNemitz ( 581327 ) on Thursday October 28, 2004 @03:07PM (#10656475) Journal
    I wonder if instead of just examining the historical record, they also took one additional factor into account.

    Physicists modelling the history of the Sun say that its overall brightness (read: activity level) has increased by about 30% since being born. This is related to the buildup of helium "ash" (from fusion of hydrogen) in its core. Furthermore, the trend is expected to continue -- quite slowly, of course. Nevertheless, any forcast that the current activity can be expected to decrease in the next few years -- or even decades -- might be rather "off" if that factor is not taken into account....

    • Innumeracy warning! (Score:5, Informative)

      by Engineer-Poet ( 795260 ) on Thursday October 28, 2004 @03:29PM (#10656672) Homepage Journal
      The Sun is approximately 4.5 billion years old. An increase in the average brightness of 30% over that time is equal to 6.7% per billion years, or .00000067% per century. If you think that this will become a measurable change in the next century, you obviously never learned anything worthwhile from a lab course (and nobody should trust you with numerical methods, either).
    • Activity is NOT heat output.



      Activity is the number of sunspots and related magnetic disturbances.

  • So... (Score:5, Insightful)

    by Jerf ( 17166 ) on Thursday October 28, 2004 @03:09PM (#10656487) Journal
    So... we'll schedule the Global Cooling panic for what, 2030-ish? That good for everyone?

    Save your Global Cooling books from the 70s, they'll be invaluable in showing how long it has been a problem even as the Global Warming hysteria is quietly, but thoroughly, whitewashed out of existance (just as the Global Cooling panic has been, as of today).

    See you then!

    (This is about 1/3 humorous, 1/3 a troll, and 1/3 an attempt to get people to be a little less dogmatic and a little more thoughful about climate issues in general. Moderate accordingly, I guess.)

    (PS: I would expect the Earth's temp, if it is affected significantly by the Sun, to lag behind it by several years, because it has one hell of a lot of "thermal inertia".)

    • RTFA (Score:1, Informative)

      by Anonymous Coward
      Except, if you had read the article, you'd see that it quite explicitly says that this study shows that solar activity does not account for the rise is global average temperature since the start of industrial revolution.
      • Umm, no. They say that since 1980, the numbers are a bit off:

        The researchers around Sami K. Solanki stress the fact that solar activity has remained on a roughly constant (high) level since about 1980 - apart from the variations due to the 11-year cycle - while the global temperature has experienced a strong further increase during that time. On the other hand, the rather similar trends of solar activity and terrestrial temperature during the last centuries (with the notable exception of the last 20 year

      • Re:RTFA (Score:4, Insightful)

        by Jerf ( 17166 ) on Thursday October 28, 2004 @03:49PM (#10656862) Journal
        AC says: Except, if you had read the article, you'd see that it quite explicitly says that this study shows that solar activity does not account for the rise is global average temperature since the start of industrial revolution.

        You mean this part?
        Whether this effect could have provided a significant contribution to the global warming of the Earth during the last century is
        an open question. The researchers around Sami K. Solanki stress the fact that solar activity has remained on a roughly constant (high) level since about 1980 - apart from the variations due to the 11-year cycle - while the global temperature has experienced a strong further increase during that time. On the other hand, the rather similar trends of solar activity and terrestrial temperature during the last centuries (with the notable exception of the last 20 years) indicates that the relation between the Sun and climate remains a challenge for further research.
        Emphasis mine. It does not say anything about whether the activity can account for the temperature. In fact, it quite explicitly disclaims any such claims in either direction. It is too soon. You need to brush up on your science skills, and your ability to read what things say instead of reading what you want them to say. If more climate fearmongers demonstrated these skills, I might actually be willing to join them in their panic. But dogma, dogma, dogma, and carefully selected evidence seems to rule the day.

        Less dogma, more science, please.

    • So... we'll schedule the Global Cooling panic for what, 2030-ish? That good for everyone?

      By that time we ought to be able to control the radiative balance to our specifications... if we get started now. We can't be certain that the solar "constant" (there's a misnomer) is going to decrease as projected, so we may still have to take measures to deal with destructive levels of warming.

      Save your Global Cooling books from the 70s, they'll be invaluable in showing how long it has been a problem even as the

      • If you expect that, how do you reconcile it with the rapid changes in temperature due to sunlight variations from Earth's axial tilt? The oceans may take years to adjust fully but we'd feel the effects much more quickly on land.

        Those are surface adjustments only. Go into a cave sometime, it holds the same temp all year long. To see the full effects of increased solar input, I would expect the big heat sinks, like the ground and the ocean which you mentioned, to take years to adjust. I would expect that to
        • That's fine if you intend to live, work, grow your crops etc. in a cave (and your water supply is still going to be affected by rainfall). I don't think that this describes too many people.

          If you go searching for data on borehole temperature measurements [uwyo.edu], you'll find that annual temperature cycles are measurable for some years as they propagate into the earth. It's true to a degree that "the temperature is always the same underground", but only to a degree; think about what "frost line" means for an exampl

    • I like the point about thermal inertia, but it raises another question: Is there such a thing as "thermal jerk?"

    • Re:So... (Score:4, Funny)

      by mcmonkey ( 96054 ) on Thursday October 28, 2004 @04:10PM (#10657087) Homepage
      I would expect the Earth's temp, if it is affected significantly by the Sun, to lag behind it by several years, because it has one hell of a lot of "thermal inertia".

      If? IF?? To say the Earth's temp is affected significantly by the Sun is understatement of an absurd degree.

      Yes, there is internal heat from radioactive decay, and perhaps some warming due to tidal forces, but I'd wager 99+% of the Earth's heat comes from the Sun.

      As for "thermal inertia" let's take the extreme case. The Sun goes bye-bye, or its energy output drops to zero. How long do expect the Earth's temp would lag? More practically, seasonal changes in weather--are they more closely tied to the positions of the Earth and the Sun today? Or their positions several years ago, due to "thermal inertia"?

      I'll see you at the next ice age!

  • I just hope we have enough hydrocarbons to survive the oncoming dark. This explains where all the light is going though: Previously reported here [slashdot.org]
  • I think this is a very significant find. The sun is the single most dominant factor in environmental conditions.

    While we know that there are ways to deflect or absorb sunlight in the earth, this only deals with a fraction of the sun's energy. For instance, putting more water in the atmosphere will "reflect" the sun's light, but even if we saturated the atmosphere with water to reflect excess incoming sunlight, we wouldn't be able to do enough should the sun increase its radiation. Conversely, if we used gr

    • Conversely, if we used greenhouse gasse to trap the sun's heat, if the sun drops in output, there will be less to trap, and the "warmest" blanket of greenhouse gasses will not be enough to keep the earth warm.

      Maybe not; I've read (though I cannot find via Google) that the Mars Society has investigated the possibility of using gases such as SF6 to create a runaway greenhouse effect on the Red Planet. If we can create a substantial atmosphere on that cold orb using 20th century chemistry, we can certainly

  • Climate change? Maybe, maybe not (Score:3, Informative)

    by iamlucky13 ( 795185 ) on Thursday October 28, 2004 @03:53PM (#10656897)

    Here's another article [space.com] that talks a little more about the findings, including a very short discussion on possible implications regarding climate change and global warming. Although a correlation makes sense and there appears to be a link between global climate change and sunspots in several instances, there is not enough data to be conclusive and the current warming trends do coincide with increasing levels of methane and CO2. It could be either or both.

    In addition to the obvious question of whether this affects our climate, the findings are interesting simply because they provide more information about our sun. I think it's amazing we can look at carbon-14 content here on earth an make inferences about the solar weather 10000 years ago. They're using this to show indirectly that the sun exhibits it's own long term "climate changes" as expected. Of course, other bodies do this as well. For example, that hurricane on Jupiter (the red spot) that's been hanging around for just a little bit longer than Frances.

  • OMFG guys! It's solar warming! Kill the Republicans!

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