More Global Warming- TSI/CO2 data

[Chris C]

I made this a new thread since everyone continues to discuss total solar irradiance (TSI)-CO2-temperature and the relationships with time. As a response to Jeremy in the other thread here, I created this excel file with data, and 3 graphs, one for TSI (1610-2000), and one for TSI (1950-2000) from data by Lean (2000), and CO2 and temperature data; CO2 prior to 1960 is from ice core data by Etheridge et al. (1998) and observational data after 1960 from observational data from Mauna Loa. Temperatures anomalies (base period 1951-1980) are from NASA GISS. TSI reconstructions are accompanied by an 11 year moving average.

 

http://files.filefront.com/CO2+Temp+TSIxls/;9527896;/fileinfo.html

 

Radiative forcings are given graphically here. They are relative to 1750, so if you do calculations from my stuff just realize that. Radiative forcing is defined by the IPCC TAR, AR4 as "‘the change in net (down minus up irradiance (solar plus longwave; in W m–2) at the tropopause after allowing for stratospheric temperatures to readjust to radiative equilibrium, but with surface and tropospheric temperatures and state held fixed at the unperturbed values"

 

 

You can get more detailed with my data, or other sources available, but just eyeballing the graph you can get very close to the changes in TSI over the last 400 years. For example, if you compare today to the Maunder Minimum you would probably eyeball a change of a about 2.5 to 3 W/m^2. To make this into a radiative forcing, you divide by 4 for the geometry of the Earth, then multiply by 0.69 (to account for albedo). To get a radiative forcing from CO2, you do 5.35 * ln (Cf/Ci) where Cf and Ci are the final and initial CO2 concentrations under the time period in consideration. Just for simplicity, we'll say that the climate sensitivity is about 0.75 C change per 1 W/m^2 change.

 

To throw in some realistic numbers, say

 

ΔT(CO2) = 5.35 * ln (380/280) * 0.75 C/W/m^2 = 1.2 C (or 2.2 F). This deviates from the observed ~0.7 C because the formula is for equilibrium conditions, so taking into account warming 'that is in the pipeline' we still have about half a degree to go even if concentrations remained constant.

 

This is about 1.6 W/m^2 compared to the maximum of about 0.3 W/m^2 depending on how you do your change of in TSI, or if you account for UV absorption in the stratosphere which would theoretically lower the RF at the tropopause. In addition, most of that TSI increase is confined to earlier in the century, so if you limit your time period to, say, the last 30 years the sun has just about no effect on the change in temperature.

[iNow]

Nice thread, Chris. Thank you for posting this.

 

Can you articulate a little more on the differences between solar irradiance, sun spots, and other "the sun did it" perspectives? There seems to be a lot of confusion on research involving solar activity and global climate, and my hope is that you have some understanding of these nuances which you can share with the rest of us.

 

 

Cheers.

[Chris C]

The sunspots themselves play a minor role - they are usually only taken as an indicator of the solar state. There are 3 proposed main mechanisms whereby changes in the sun affect our climate:

 

1 - change in TSI

 

2 - change in solar UV, which alters the absorption of energy in the stratosphere and the temperature of the upper atmosphere. May affect circulation and distribution of heat.

 

3 - change in galactic cosmic rays (GCR). Svensmark & co reckon the GCR affects the cloudiness. Others, such as Tinsley, think it affects the atmospheric fairweather electric field, which again may have an effect on the cloud micro-physics

 

This is a good book on the subject

http://www.amazon.com/Activity-Earths-Climate-Rasmus-Benestad/dp/3540433023

[bascule]

There are 3 proposed main mechanisms whereby changes in the sun affect our climate:

 

1 - change in TSI

 

2 - change in solar UV, which alters the absorption of energy in the stratosphere and the temperature of the upper atmosphere. May affect circulation and distribution of heat.

 

3 - change in galactic cosmic rays (GCR). Svensmark & co reckon the GCR affects the cloudiness. Others, such as Tinsley, think it affects the atmospheric fairweather electric field, which again may have an effect on the cloud micro-physics

 

Thanks. That's the list I've been looking for, but all I've gotten out of the proponents of this theory are unscientific ramblings about how the actual mechanisms are unknown.

 

This is good stuff to know.