The earth acts as a block body so it's input energy must approximate its output energy or its temperature changes. So what magnitude change in input energy would equal a change of .7f? Well black body radiation (power out) = (T1^4 - T2^4) [in kelvin] so 1.0057x the power output or .57% but the estimated change in solar output is ~0.1% variation over the last 2,000 years which does not add up.
Granted the global temperature is not uniform and the earth is not a true black body but these numbers are not even close and it would take a huge swing in solar activity to get changes in the 1+ deg range.
They disappear every ~11 years and have been for a while but the next cycle has not started yet so some people think it might be while. Anyway, check: (http://en.wikipedia.org/wiki/Solar_variation)
Edit: If you graphed solar radiation received at the outer surface of Earth's atmosphere you would see solar output over the last 100 years as a long line of 1,366w/m with some peaks at 1,367w/m and a possible drop into 1,365 territory.
I'm not yet convinced that all of the various climatic processes on Earth are well-enough understood to say definitively, "x is causing y".
The Earth doesn't even quite count as a black body because of its varying albedo; but regardless of its astronomical thermal reflectiveness, there are all of these really complex interactions in its own climate, where possibly a small change in initial state (the sun's temperature) could result in a large change in effect.
At the moment, the best that anybody has is correlative evidence, and I haven't seen a large enough change in human activity planet-wide to account for a .7 degree change either.
Can any of the physics gurus here offer an explanation of how sunspot activity is related to heat output? It doesn't really explain that in the article. Less heat output means less fusion reaction, means less magnetic activity, means lack of sunspots, I presume?
Since sunspots are darker than the surrounding photosphere it might be expected that more sunspots would lead to less solar radiation and a decreased solar constant. However, the surrounding margins of sunspots are hotter than the average, and so are brighter; overall, more sunspots increase the sun's solar constant or brightness.
But if this were the cause, wouldn't sunspots put our global temperature in constant flux as the spots themselves migrate and as we orbit and move toward/away from them?
The sun is actually a very good insulator. All the heat is generated in the middle and takes millennia to reach the top.
So anything that basically "mixes" the sun will cause more heat to be emitted. No sun spots=no mixing, and all the heat remains trapped.
I think that after trapping heat for so long, the sun gets hotter and generates more sun spots because of all the extra energy. The sun spots bleed it out, and the cycle continues.
Uh, what? Sun spots come from the magnetic flux tubes from the inner layers becoming unstable and rising to the surface, forming loops. If anything, I'd guess that sunspots inhibit the flow. The mixing happens mostly because of the persistent convection cells in the sun and of course the turbulence.
I don't know offhand the answer to the parent's question, but in my experience, the above doesn't make sense.
Convection cells are the baseline mixing, but any activity in the sun, and sun spots are far from quiet areas, despite being dark, would cause additional mixing.
Why would you say sunspots would inhibit the flow?
"magnetic flux tubes" would not arise from nothing, they would arise from large amounts of ions moving (making an electrical current), and therefor mixing the suns layers.
The magnetic activity doesn't come from the fusion reaction directly. The sun has a differential rotation profile. Some layers rotate faster than others. This stretches the magnetic flux tubes as they pass through these layers, increasing their strength. If you drop some oil in a river which is not moving at a uniform speed, the oil spot will get deformed and stretched.
(it sounds like voodoo magic, I hate that explanation, but it's the textbook version as far as I can remember)
Also, the statement "That period coincided with a little ice age on Earth that lasted from 1650 to 1700" is inaccurate. Actually, the period from 1650 to 1700 is not for the little ice age, but for the Maunder Minimum, the previous period when there were few sunspots. The little ice age has no sharp beginning, and is variously said to start almost anywhere after the medieval warm period - say anywhere from mid-14th century to the mid-17th century. The little ice age ended with the beginning of global warming in the mid-19th century.
In competitive academic debate, we've long been reading evidence that we're 'due' for a new period of global cooling and so all the global warming activity is good because it's helping stave off the next ice age.
Indeed, in the 1970s the "green" movement was very worried about a new ice age, and the solutions they proposed to global cooling were, strangely, almost the same solutions now proposed to combat global warming.
There are always wacko's saying the end is near but most of them are far from credible. Unfortunately it can be hard to tell who is full of it when they extrapolate past reason. Anyway, particulate matter does lower global temperatures but unlike CO2 it does not stay up for vary long.
Veering off-topic, but you do CEDA/NDT style debate too? (aka policy debate in high school) Nice, I don't know any other hacker debaters. Drop me a line (email in my profile), I'd be interested in bouncing some ideas about some debate-related projects off of you.
NASA solar physicist David Hathaway thinks that this is mostly alarmist nonsense, and after looking at his solar cycle graph, I'm inclined to agree with him. The Maunder Minimum was a huge departure from the cycle, and it's far too early to extrapolate and assume a similar departure.
Whatever it is, what does it matter if we can't predict what's going to happen? As far as we know, the world's getting warmer and its time to start buying priuses wherever we can afford them ;)
Agreed. My former advisor was as good as anyone in that field. He has a very good introduction (... for a grad course in physics) to the dynamo problem (aka.: the solar cycle) at http://solarphysics.livingreviews.org/Articles/lrsp-2005-2/
It is fair to say that solar dynamo modelling has not yet recovered from this four-way punch, in that nothing remotely resembling concensus currently exists as to the mode of operation of the solar dynamo
From the Brief historical survey, which is at least partly readable.
30 comments
[ 3.5 ms ] story [ 118 ms ] threadGranted the global temperature is not uniform and the earth is not a true black body but these numbers are not even close and it would take a huge swing in solar activity to get changes in the 1+ deg range.
PS: La Niña - is the likely culprit.
Edit: If you graphed solar radiation received at the outer surface of Earth's atmosphere you would see solar output over the last 100 years as a long line of 1,366w/m with some peaks at 1,367w/m and a possible drop into 1,365 territory.
The Earth doesn't even quite count as a black body because of its varying albedo; but regardless of its astronomical thermal reflectiveness, there are all of these really complex interactions in its own climate, where possibly a small change in initial state (the sun's temperature) could result in a large change in effect.
At the moment, the best that anybody has is correlative evidence, and I haven't seen a large enough change in human activity planet-wide to account for a .7 degree change either.
Since sunspots are darker than the surrounding photosphere it might be expected that more sunspots would lead to less solar radiation and a decreased solar constant. However, the surrounding margins of sunspots are hotter than the average, and so are brighter; overall, more sunspots increase the sun's solar constant or brightness.
So anything that basically "mixes" the sun will cause more heat to be emitted. No sun spots=no mixing, and all the heat remains trapped.
I think that after trapping heat for so long, the sun gets hotter and generates more sun spots because of all the extra energy. The sun spots bleed it out, and the cycle continues.
I don't know offhand the answer to the parent's question, but in my experience, the above doesn't make sense.
Why would you say sunspots would inhibit the flow?
"magnetic flux tubes" would not arise from nothing, they would arise from large amounts of ions moving (making an electrical current), and therefor mixing the suns layers.
(it sounds like voodoo magic, I hate that explanation, but it's the textbook version as far as I can remember)
http://science.nasa.gov/headlines/y2008/11jul_solarcycleupda...
NASA solar physicist David Hathaway thinks that this is mostly alarmist nonsense, and after looking at his solar cycle graph, I'm inclined to agree with him. The Maunder Minimum was a huge departure from the cycle, and it's far too early to extrapolate and assume a similar departure.
http://www.spaceweather.com
Space Weather tracks daily sunspot activity, as well as lots of other cool tidbits of current astronomy.
"In the early 20th century there were periods of quiet lasting almost twice as long as the current spell."
"In summary, "the current minimum is not abnormally low or long.""
"Hathaway anticipates more spotless days, maybe even hundreds, followed by a return to Solar Max conditions in the years around 2012."
Along with some interesting graphs, it looks like everything is business as usual for the sun.
A google search on the author, Rebecca Sato, shows that she typically writes lots of "what if" and other fluff pieces.
Sounds like fear mongering to me.
Temperature peaked in 1998.
It is fair to say that solar dynamo modelling has not yet recovered from this four-way punch, in that nothing remotely resembling concensus currently exists as to the mode of operation of the solar dynamo
From the Brief historical survey, which is at least partly readable.
What is important is the systems at work within the sun. A blank sun is the calm before the storm.
Solar flare : Dec 21st, 2012.