There are many aspects of it, and taking them into account in climate models that attempt to predict future warming is difficult at best. http://environmentblog.ncpa.org/climate-...
For example, cosmic radiation http://en.wikipedia.org/wiki/Cosmic_radi...
promotes the formation of high altitude clouds. http://en.wikipedia.org/wiki/Cosmic_radi...
This in turn increases the albedo of Earth, http://en.wikipedia.org/wiki/Albedo
and has a cooling effect. Note that there is an inverse correlation between sun spots and cosmic radiation. http://en.wikipedia.org/wiki/File:SpaceE...
There is a natural human tendency to simplify calculations that are poorly understood, or leave them out entirely, and then to believe whatever the computer spits out, no matter how poorly the understanding of the underlying equations were. http://www.nipccreport.org/articles/2010...
What is well understood, is that the albedo of Earth is a variable that depends on cloud formation (36% - 78%), forestation (6% - 14%), ice (32% - 38%)/snow cover (37% - 90%), and urbanization. Earth's albedo varies, but is about 30%. The total solar intensity (TSI) is tends to be between 1.3 KW/m^2 and 1.4 KW/m^2 at the top of the atmosphere, [1] and correlates to the sun spot index. http://www.woodfortrees.org/plot/uah-lan...
What is known well is how black bodies behave. This is translated to the grey body that Earth is by way of the Stefan–Boltzmann law for energy output (j) based on the temperature (T), a constant (S) and the efficienty (E): [2]
j = ES(T^4)
and that:
energy in = TSI * Albedo = energy out = ES(T^4)
E ~ 60%
and depends on such things as the greenhouse effect, which also, is poorly understood. Thus, it is fairly easy to assume some variation in TSI over the 11 year solar cycle and back figure the effect on temperature based on the Stefan-Boltzmann equation, then fiddle with other things. including cosmic radiation effects on Albedo, which is dismissed by the IPCC. [3] There are other effects on the Albedo. It is not really known how much the ice caps will change, how snow fall will change, or how much deforestation will happen. Modeling these is difficult at best. These things are likely to be treated in a very simplified manner, or not at all. Nevertheless, they each might be more important than atmospheric CO2 concentration that tends to be the dominate factor in IPCC accepted climate models. The greenhouse effect of gases is dependent on the spectral release of the Sun, which in turn is another major variable that is probably not adequately treated by the IPCC. [4] In fact, the IPCC does the normal thing that humans do when assigned to model something that is beyond the capabilities of current technology to do adequately, and presumes:
"Each of the above 3 assumptions for the existence of a significant long-term irradiance component is now questionable." -- [3] paragraph 2 page 62.
That way, they can effectively justify their tendency to ignore long term (30 years) solar effects on temperature trends.
Edit @John: "zero scientific data that would suggest that our increasing of the atmospheric CO2 levels will not also increase global temperatures beyond the natural variations"
Would that be in kelvins per century, or nanokelvins per century? [5]
Are you still looking for that loophole in the AGWT, Mike? Well, if it is to be found, it will be through the use of science so I appreciate a science based question from you.
"We know there are many metrics and variables in solar activity."
True
"geomagnetic effects" - http://www.megakastro.gr/weather_agro/so...
There are some that believe that Earth's geomagnetic field has played a part in Earth's past climate changes, but there is no evidence that a change in the geomagnetic field would have been a forcing in past climate change events. Also, the geomagnetic field is stronger at the poles and weaker along the lower latitudes. The anomalous warmth we have witnessed is greater at the poles and this is counter intuitive of what you would expect if the geomagnetic field were a forcing in climate change.
"solar wind" - http://en.wikipedia.org/wiki/Solar_wind
Solar winds, if a climate driver, would show across all of the objects within our solar system. The only caveat to this would be with the other natural variations within that object's climate.
"solar proton event" - http://en.wikipedia.org/wiki/Solar_proto...
Now you really are reaching. But, as long as your looking for loopholes?
"ambient plasma"
??? You are just being funny, right?
"solar radiance (TSI?)" - http://data.giss.nasa.gov/gistemp/2010su...
How many times has this been discussed?
Here is a link that discusses most of what you want to know - http://www.skepticalscience.com/solar-ac...
"Given the range of the types of variation the Sun can undergo, what solar parameters are used in climate models?"
Everything that is known to influence the climate is incorporated into the long run climate models. I have read reports where some of the short run climate models are looking at the short term climate variables on a more individual basis to better understand the short term anomalies. This is to provide better data for the long term model runs. The goal of the climate model coders is to improve the data that goes into the code to achieve better performing long run climate models. These are fine tuning mechanisms since the climate models used previously have shown to be within the range of probabilities these earlier models produced.
At the end of the day, Mike, there is zero scientific data that would suggest that our increasing of the atmospheric CO2 levels will not also increase global temperatures beyond the natural variations within the global climate. I repeat, zero scientific data to support this. Should you possess such scientific data, then I encourage you to share it with us.
Added***
Mike, the solar cycles are fairly well understood. - http://istp.gsfc.nasa.gov/earthmag/sunsp...
The cycles of the geomagnetic events are too short in duration to be a global climate changer. Much in the way that the Enso is, it is not much more than "noise" within the climate models and does not produce any long term trends on our global climate.
You can't possibly expect an answer to such a complex question in YA. Not only are there various parameters as you suggest, there are various models and the importance of solar variability varies depending on whether you are looking to project global average temperatures, or local weather probabilities.
My suggestion, short of enrolling in a university course or program, would be to read the research made available at the National Academy of Science.
The Effects of Solar Variability on Earth's Climate: A Workshop Report
http://www.nap.edu/catalog.php?record_id...
"Even small variations in the amount or distribution of energy received at Earth can have a major influence on Earth’s climate when they persist for decades. However, no satellite measurements have indicated that solar output and variability have contributed in a significant way to the increase in global mean temperature in the past 50 years. Locally, however, correlations between solar activity and variations in average weather may stand out beyond the global trend; such has been argued to be the case for the El Ni?o-Southern Oscillation, even in the present day."
The answer is none, they do not count solar as important, they state that TSI varies 0.1% which has next to no effect on earths temperature.
The fact that Earths temperature closely follows the suns cycles is dismissed as coincidence,
It is certain the sun has a major effect on our climate, and just because we do not know the mechanics behind it changes nothing.
Well, I'm not an expert but I think it goes something like this:
We have lots of proxy data for historic temperatures from ocean/lake sediments, tree-rings, coral bands, ice cores, etc. From this we've reconstructed things like the Medieval Maximum around 1000 AD and the Little Ice Age from around 1600 - 1800.
Now, stellar activity in our galaxy produces energetic particles (yes, the sun also produces them but that's not the point!). This cosmic radiation constantly collides with the earth and, since it has high energy, it causes nuclear fragmentation reactions to occur. The impact of these particles slightly adjusts the natural ratio of isotopes of, for example, carbon and beryllium. When the sun is going through periods of high activity, its magnetic field also increases. This has the effect of deflecting the charged particles from our galactic neighbours away from the earth. So, one proxy for solar activity is performed by examining the ratio of isotopes in ice (beryllium) or trees (carbon).
When we compare the proxy temperature data of the Little Ice Age and the proxy solar activity data, there appears to be correlation - the Maunder minimum coincides. This gives climatologists a rough measure of climate sensitivity to solar output since it suggests, but doesn't prove, that most of the observed change in climate between 1600 and 1800 was due to solar activity.
The value, roughly, is that an increase in solar output of 0.14% accounted for an increase in global temperatures of 0.28C. This is for pre-industrial times. If that same sensitivity is applied from 1850 to today and you take into account the 0.13% increase in solar radiation over that time, the temperature increase due to the sun would be about half that actually observed. If applied from 1970 to today, it would account for 1/3rd of the observed warming.
So, that in a nutshell is how they model it. It's not based on estimates of various parameters but on historical proxy temperature and solar output data to obtain a value for the sensitivity.
I am not a climate modeller and can't answer the question directly but it is obviously pretty hard to model something that has unknown characteristics. It is fascinating that a giant ball of hydrogen slowly fusing a small portion into helium behaves with these cyclical and complex patterns.
difficult point. browse into yahoo. that will may help!
"We know" lots of things from your past "questions."
We know there are many metrics and variables in solar activity. For example, there are geomagnetic effects, solar wind, solar proton events, ambient plasma, etc. There's also irradiance levels such as total solar irradiance and ultraviolet irradiance.
There are also several solar cycles of which the most well known is the 11 year sunspot cycle (Schwabe cycle) along with cycles of 22 years (Hale cycle), 87 years (Gleissberg cycle), 210 years (Suess cycle) and 2300 years (Hallstatt cycle).
There are also indirect effects of the variance of the Sun. For example, changes to the solar wind will change the amount of cosmic rays penetrating the atmosphere which may or may not have a significant climatic effect. Or the effects of UV radiation on the stratosphere (e.g. ozone). There are likely more we don't yet know about.
Given the range of the types of variation the Sun can undergo, what solar parameters are used in climate models?
