Sun's Activity Levels Reconstructed

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."

Comments

Innumeracy warning!

[Engineer-Poet]

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).

RTFA

[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.

Climate change? Maybe, maybe not

[iamlucky13]

Here's another article 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.

Re:A germ of truth, but I fault the conclusion

[Engineer-Poet]

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, 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 example.

Re:Error Bars

[Idarubicin]

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. 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.