Decrease in Solar Activity Predicted: is Global Cooling imminent?

[spidergoat]

That would be a false conclusion. The greenhouse effect may be natural, but present levels of greenhouse gasses are almost certainly caused by human activities.

The concentrations of CO2 and methane have increased by 36% and 148% respectively since 1750.[40] These levels are much higher than at any time during the last 800,000 years, the period for which reliable data has been extracted from ice cores.

Less direct geological evidence indicates that CO2 values higher than this were last seen about 20 million years ago.(wikipedia)

Are we ready for the climate of 20 million years ago? This would be a completely new situation for most life on Earth.

 

[adoucette]

Remember only about half of the warming since the middle of the last century is blamed on Anthropogenic effects and so the climate can indeed change due to a drop in the Sun's output and so a long and significant cooling period of the sun could definately reverse the warming trend that we have been having due to increasing GHGs.

In which case we might, if the sun's output goes down enough, after several decades of cooling trends, be trying to figure out how to pump GHGs into the atmosphere.

 

[Believe]

I don't think there is any precise balance. A decrease in solar output would only slow the warming slightly. It's been a long time since solar output was the most significant factor.

? A large decrease in solar activity could freeze the earth solid. It could easily become the most significant factor. I'm not saying that it requires a precise balance, I'm saying that to make your claim (without being full of crap) you would have to know that balance, which you obviously do not so your claim is speculation at best, crap at worst.

 

[spidergoat]

It just doesn't vary to that degree.

 

[Believe]

It just doesn't vary to that degree.

Really, the little ice age was just a........... oh wait.

 

[spidergoat]

Yeah... little. It was probably caused by an interruption in the Atlantic current caused by a huge release of fresh water.

 

[Trippy]

Variation in solar irradiance at the top of the atmosphere, compared to 10.7 cm radio flux, solar flare index, and sunspot observations for the last three solar cycles.

Note that the variation in solar irradiance is on the order of 0.75 w/m[sup]2[/sup]

Note also that - irrespective of whether or not you accept the degree of variability for forcing:

The solar forcing model used by NASA/GISS to feed into their GCM, includes solar variability.

 

[Believe]

Yeah... little. It was probably caused by an interruption in the Atlantic current caused by a huge release of fresh water.

Honestly I don't think it will matter either (not gonna lose sleep over it), but it could. You can't just dismiss it off hand as such when it could hold some merit.

 

[Trippy]

Honestly I don't think it will matter either (not gonna lose sleep over it), but it could. You can't just dismiss it off hand as such when it could hold some merit.

We can, however, set reasonable limits on it based on historical observations.

 

[Believe]

We can, however, set reasonable limits on it based on historical observations.

Right, the historical observation is the little ice age. Now we don't know how it happened (volcanoes, meteor, aliens, ext.....) but we if we assume was due to a variation in the suns output (one of the theories) then you could try to crunch some numbers based on that. This however has not been done (unless it has please show us) so you can't make that kind of statement (at least not in a reliable way).

Still, I need to stop arguing this because I also believe it won't make a difference.

 

[adoucette]

Note that the variation in solar irradiance is on the order of 0.75 w/m[sup]2[/sup]

Note also that - irrespective of whether or not you accept the degree of variability for forcing:

The solar forcing model used by NASA/GISS to feed into their GCM, includes solar variability.

Well RECENT variability is .75 w/m[sup]2[/sup]

But as your chart only goes back to 1850, we know that the sun can get quite a bit less active then that.

http://upload.wikimedia.org/wikipedia/commons/5/5c/Carbon14_with_activity_labels.svg

So it is entirely possible for the Earth to get quite a bit cooler then it is today even with the level of GHGs if the sun decides to take a 500 year or longer powder.

Arthur

 

[Trippy]

Right, the historical observation is the little ice age.

A Historical event that is far from being consistent. According to the IPCC, the average cooling produced by the LIA was 1k, however varied from region to region, with some areas seeming to recieve more cooling than others. The LIA was also divided into two periods by a warm period (the medieval warm period).

The LIA began as early as 1250-1300, where the Maunder Minimum didn't begin until 1645, 300 years after the LIA began. In fact, 1250-1300 corresponds with a period during which, at least according to solar activity proxies, solar activity was similar to (though reduced a little from) what it is now, and was comparable to the previous 300 years activity (excluding the Oort Minimum (1010-1050).

The Maunder minimum just happened to coincide with the coldest part of the LIA, which is why an influence is suggested.

Now we don't know how it happened (volcanoes, meteor, aliens, ext.....) but we if we assume was due to a variation in the suns output (one of the theories) then you could try to crunch some numbers based on that.

This is wrong - the LIA can't have been caused by the Maunder minimum, unless you want to suggest that the sun is capable of temporal engineering and violating causality. It may have made matters a little worse, however.

However, once again we come back to the basic point which you seem to have missed - if you're invoking sunspots as a causal agent for activity causing heating, then there's only so far that it can vary.

This however has not been done (unless it has please show us) so you can't make that kind of statement (at least not in a reliable way).

Yes, I can, and I believe the evidence supports making such a statement.

Still, I need to stop arguing this because I also believe it won't make a difference.[/QUOTE]
Whilst I am uncertain of Spidergoats assessment, I am confident we can rule out a snowball earth hypothesis.

Sure, if the minimum continues for long enough, Londoners might once again be able to ice skate on the thames river during winter, however that falls a long way short of the sort of snowball earth scenario you seem to be suggesting.

 

[Trippy]

Well RECENT variability is .75 w/m[sup]2[/sup]

I didn't claim otherwise, did I?
Did I not point out that the chart only covers the last three solar cycles?

But as your chart only goes back to 1850, we know that the sun can get quite a bit less active then that.

Again, I don't recall suggesting otherwise. As I said, it's the solar forcing model that NASA and the GISS use for the GCM, which also only goes back to 1850. The point that I was making by using that graph was to illustrate that the GCM includes solar variability in its forcing model, as I stated in the sentence under the image. Nothing more.

http://upload.wikimedia.org/wikipedia/commons/5/5c/Carbon14_with_activity_labels.svg

That would be one of the Proxies that I was referring to in post 32, yes, however, if your going to link to an SVG, you're better off linking to one of the rendered PNG's like this one.

Because not everybodies browsers can render .SVG's

I considered linking to this graph, but decided not to becaus eof the issue with SVG's (yes, I keep forgetting about the rendered PNG's as well).

So it is entirely possible for the Earth to get quite a bit cooler then it is today even with the level of GHGs if the sun decides to take a 500 year or longer powder.

Arthur

I don't see, neccessarily, a 500 year powder in that data, what I do see, however, is a general 500 year decline in the values of local minima and maxima.

None of which actually changes my stance as expressed in post #32, to be honest, aside from the fact that I'm going to restate that I believe we can definitively rule out a snowball earth scenario.

 

[madanthonywayne]

Historically, humans didn't exist.

There were plenty of humans around during the Maunder Minimum aka "little ice age".

 

[Believe]

A Historical event that is far from being consistent. According to the IPCC, the average cooling produced by the LIA was 1k, however varied from region to region, with some areas seeming to recieve more cooling than others. The LIA was also divided into two periods by a warm period (the medieval warm period).

The LIA began as early as 1250-1300, where the Maunder Minimum didn't begin until 1645, 300 years after the LIA began. In fact, 1250-1300 corresponds with a period during which, at least according to solar activity proxies, solar activity was similar to (though reduced a little from) what it is now, and was comparable to the previous 300 years activity (excluding the Oort Minimum (1010-1050).

The Maunder minimum just happened to coincide with the coldest part of the LIA, which is why an influence is suggested.


This is wrong - the LIA can't have been caused by the Maunder minimum, unless you want to suggest that the sun is capable of temporal engineering and violating causality. It may have made matters a little worse, however.

However, once again we come back to the basic point which you seem to have missed - if you're invoking sunspots as a causal agent for activity causing heating, then there's only so far that it can vary.


Yes, I can, and I believe the evidence supports making such a statement.

Still, I need to stop arguing this because I also believe it won't make a difference.

Whilst I am uncertain of Spidergoats assessment, I am confident we can rule out a snowball earth hypothesis.

Sure, if the minimum continues for long enough, Londoners might once again be able to ice skate on the thames river during winter, however that falls a long way short of the sort of snowball earth scenario you seem to be suggesting.[/QUOTE]

I got served.

 

[spidergoat]

Even if the hypothesis is correct, it will only postpone the inevitable.

 

[Trippy]

Even if the hypothesis is correct, it will only postpone the inevitable.

Yus.

It certainly falls short of a long term fix, and may just give us more time to take some kind of action.

 

[Trippy]

There were plenty of humans around during the Maunder Minimum aka "little ice age".

No, they are not synonymous.

 

[James R]

Evidence from mountain glaciers does suggest increased glaciation in a number of widely spread regions outside Europe prior to the 20th century, including Alaska, New Zealand and Patagonia. However, the timing of maximum glacial advances in these regions differs considerably, suggesting that they may represent largely independent regional climate changes, not a globally-synchronous increased glaciation. Thus current evidence does not support globally synchronous periods of anomalous cold or warmth over this time frame, and the conventional terms of "Little Ice Age" and "Medieval Warm Period" appear to have limited utility in describing trends in hemispheric or global mean temperature changes in past centuries... [Viewed] hemispherically, the "Little Ice Age" can only be considered as a modest cooling of the Northern Hemisphere during this period of less than 1°C relative to late 20th century levels.​

Source

See also:

Maunder minimum

In particular, look at the graph of solar activity on the top right of the page.

There doesn't look to be any evidence of a Maunder-like minimum occurring now.

More:

http://www.eh-resources.org/timeline/timeline_lia.html

And:

Press accounts of the new solar reports played up the Maunder Minimum angle, hinting that it might happen again. Some even implied that global warming might be counteracted.

In fact, the meaning of the latest sunspot reports is still being debated, as Andrew Revkin at Dot Earth has chronicled. But even if they really do portend a decades-long solar lull, studies already point to a minimal effect on climate.

Most Little Ice Age cooling appears to have been the result of coincidentally high volcanic activity that cloaked Earth in sunlight-blocking soot. As for the sun, a study published in 2001 in Science found that reduced solar activity produced a cooling effect of about 0.5 degrees Fahrenheit. In other estimates, the cooling is even more insignificant.

‘Global mean temperatures in the year 2100 would most likely be diminished by about 0.1°C.’

More recently, in a 2010 Geophysical Research Letters study, Georg Fuelner and Stefan Rahmstorf of the Potsdam Institute for Climate Impact Research asked the question directly: What would happen if Earth experienced another 70-year-long solar minimum?

The answer can be seen in the following image, which estimates the temperature difference between a solar minimum future under “middle-of-the-road” climate scenarios and the Maunder Minimum. In a nutshell: It’s going to be much, much hotter in the future, solar minimum or not.​

Source

 

[James R]

11 years up and 11 years down. That makes a 22 year cycle. It's basic Meteorology 101.

11 years field up and then back to zero, followed by another 11 years field down and then back to zero.

"Hale's observations revealed that the solar cycle is a magnetic cycle with an average duration of 22 years. However, because very nearly all manifestations of the solar cycle are insensitive to magnetic polarity, it remains common usage to speak of the "11-year solar cycle".

In particular, solar activity is insensitive to magnetic polarity, so that solar activity follows an 11 year cycle.

The solar variability we've seen over the last hundred years or so has been minimal. But if the decrease in activity is on the order of the Maunder Minimum, no one can say for sure what effect it would have. History, however, would suggest a quite large effect.

It looks like it has been pretty thoroughly modelled to me.