Some Basic Calculations, Data and Questions

[blizzard1024]

I probably shouldn't start another thread but I have some questions that are pretty

basic and I haven't been able to find a satisfactory answer on-line in the many

references from this thread and other websites. Please forgive me for the basic

stuff but I believe I have some valid questions that if someone can point

me in the right direction I would appreciate it.

First, consider the following equation ΔF = 5.35 ln (C1/C0) where ΔF is the change

in radiative forcing in watts/m2. C1 is new CO2 conc. and C0 is the preindustrial

concentration. If you double CO2 you get around 3.7 W/m2 forcing where

using the Stefan Boltzmann equation you get around 1.2C of warming without feedbacks.

This is very basic.

Using Wien's Displacement Law, the temperature where CO2 is opaque to the IR

is around -50C which corresponds to its absorption band centered around 15 microns wavelength.

Hence CO2's main absorption band lies in the upper troposphere where there is

much less water vapor and there is little if any overlap. In the lower troposphere, CO2 is

transparent to the IR since its absorption's band don't correspond to most surface

temperatures (except Antarctica and Siberia at times). So the upper troposphere

by doubling CO2 will absorb more IR at around -50C on the edges of the 15 micron absorption

band since it is not nearly "saturated" at these high levels.

So by doubling CO2, this leads to more outgoing long wave at colder temperatures(-50C) and an imbalance

causes the troposphere to warm to alleviate this imbalance since less energy escapes at lower temperatures.

Hence the net forcing of around 3.7 w/m2 for a doubling of CO2. Conversely there is more emission in

the stratosphere so hence the stratosphere cools. Net energy in from the sun equals net energy out

by long wave emission. Energy is not created by adding an IR active substance to the atmosphere.

Ok. All is good here. Basic greenhouse effect 101 is understood. Pretty easy.

First question is where does the 5.35 factor come from in the logarithmic equation.

All I could find is a calculation from a 1D model. Isn't this derived from spectroscopy or

some other more rigorous way? A model especially 1D is troublesome in my opinion.

Second, if you use this 5.35 factor in the above equation and assume a pre-industrial

CO2 level of 280 ppm and plug in today's concentration of around 390 ppm you get around 1.8 W/m2

extra forcing. If you assume the amount of incoming radiation from the sun is 239 W/m2 and you

increase the forcing by 1.8 w/m2 you get around .6C of warming using S-F equation. This is without feedbacks.

The observed rise in temperature based on HADCRUT4 is around .8C so far. So, this would assume

if there are feedbacks they are slightly positive, the whole warming we have seen is from the

increased CO2. But it has been stated that natural warming occurred to 1940 so this means

that the recent warming which is blamed on increased CO2 is just under .6C eyeballing HADCRUTv4 graph since

1940 or so. suggesting neutral to slightly negative feedbacks at work.

Even if the warming of whole period between 1850 and 2010 is from CO2 ignoring the fact

that there was a little ice age...that would equal about .8C which would suggest

a very small positive feedback and given the logarithmic nature of increasing CO2

concentrations we likely would not see catastrophic warming. Again, the data

presently supports this notion that a modest warming at best would take place. Of course,

some say there is warming in the "pipeline" that we are already "committed" to

even if CO2 concentrations stop rising. Where is this so called warming in the pipeline??? In

the oceans?? OHC has risen but how can you not rule out Solar forcing which has

leveled off?? If you believe the premise that there is warming in the pipeline from CO2

increases, then there are obviously significant lags in the climate system which actually

makes sense because the planet is dominated by water which has a high specific heat

content. So we all know we have had a maximum in Solar activity in the late

20th century which has stopped and now slightly reversed. But, how can you rule out that

the continued warming until 1998 and the recent lack of significant warming is not just a

response to solar variability? I don't see how CO2 can have a lag effect but the sun can't

is what I am saying. What gives here?

Thanks and happy holidays.

[WeatherRusty]

I probably shouldn't start another thread but I have some questions that are pretty

basic and I haven't been able to find a satisfactory answer on-line in the many

references from this thread and other websites. Please forgive me for the basic

stuff but I believe I have some valid questions that if someone can point

me in the right direction I would appreciate it.

First, consider the following equation ΔF = 5.35 ln (C1/C0) where ΔF is the change

in radiative forcing in watts/m2. C1 is new CO2 conc. and C0 is the preindustrial

concentration. If you double CO2 you get around 3.7 W/m2 forcing where

using the Stefan Boltzmann equation you get around 1.2C of warming without feedbacks.

This is very basic.

Using Wien's Displacement Law, the temperature where CO2 is opaque to the IR

is around -50C which corresponds to its absorption band centered around 15 microns wavelength.

Hence CO2's main absorption band lies in the upper troposphere where there is

much less water vapor and there is little if any overlap. In the lower troposphere, CO2 is

transparent to the IR since its absorption's band don't correspond to most surface

temperatures (except Antarctica and Siberia at times). So the upper troposphere

by doubling CO2 will absorb more IR at around -50C on the edges of the 15 micron absorption

band since it is not nearly "saturated" at these high levels.

So by doubling CO2, this leads to more outgoing long wave at colder temperatures(-50C) and an imbalance

causes the troposphere to warm to alleviate this imbalance since less energy escapes at lower temperatures.

Hence the net forcing of around 3.7 w/m2 for a doubling of CO2. Conversely there is more emission in

the stratosphere so hence the stratosphere cools. Net energy in from the sun equals net energy out

by long wave emission. Energy is not created by adding an IR active substance to the atmosphere.

Ok. All is good here. Basic greenhouse effect 101 is understood. Pretty easy.

First question is where does the 5.35 factor come from in the logarithmic equation.

All I could find is a calculation from a 1D model. Isn't this derived from spectroscopy or

some other more rigorous way? A model especially 1D is troublesome in my opinion.

Second, if you use this 5.35 factor in the above equation and assume a pre-industrial

CO2 level of 280 ppm and plug in today's concentration of around 390 ppm you get around 1.8 W/m2

extra forcing. If you assume the amount of incoming radiation from the sun is 239 W/m2 and you

increase the forcing by 1.8 w/m2 you get around .6C of warming using S-F equation. This is without feedbacks.

The observed rise in temperature based on HADCRUT4 is around .8C so far. So, this would assume

if there are feedbacks they are slightly positive, the whole warming we have seen is from the

increased CO2. But it has been stated that natural warming occurred to 1940 so this means

that the recent warming which is blamed on increased CO2 is just under .6C eyeballing HADCRUTv4 graph since

1940 or so. suggesting neutral to slightly negative feedbacks at work.

Even if the warming of whole period between 1850 and 2010 is from CO2 ignoring the fact

that there was a little ice age...that would equal about .8C which would suggest

a very small positive feedback and given the logarithmic nature of increasing CO2

concentrations we likely would not see catastrophic warming. Again, the data

presently supports this notion that a modest warming at best would take place. Of course,

some say there is warming in the "pipeline" that we are already "committed" to

even if CO2 concentrations stop rising. Where is this so called warming in the pipeline??? In

the oceans?? OHC has risen but how can you not rule out Solar forcing which has

leveled off?? If you believe the premise that there is warming in the pipeline from CO2

increases, then there are obviously significant lags in the climate system which actually

makes sense because the planet is dominated by water which has a high specific heat

content. So we all know we have had a maximum in Solar activity in the late

20th century which has stopped and now slightly reversed. But, how can you rule out that

the continued warming until 1998 and the recent lack of significant warming is not just a

response to solar variability? I don't see how CO2 can have a lag effect but the sun can't

is what I am saying. What gives here?

Thanks and happy holidays.

The constant 5.35 derives from the output of radiative transfer models fed line-by-line transfer codes obtained through the Hitran Database.

Myhre et al.

The 'warming in the pipeline' is represented by the remaining TOA energy imbalance. The surface must radiate at a higher temperature than at present in order to eliminate the current imbalance. The current global average temp balances the total anthropogenic forcing from a time back in the 1980s.

[skierinvermont]

Well I can't answer a couple questions without doing some further reading, but I have two points:

1) I'm not sure where you're getting this -50C from. The atmosphere is constantly emitting in ALL wavelengths. A substance at 15C still is just an average of the kinetic energy of all the particles.. some have much more some have much less.

2) Regarding the proportion of warming thus far that has been anthropogenic I would agree about ~.6C of the total .8C since 1900. However, the earth remains in a large energy imbalance around .6W/m2. Which means that only 1.2W/m2 of the total 1.8W/m2 has taken effect. 1.2W/m2 has caused .6C, which means 3.7W/m2 would cause 1.8C.

That is on the very low end of the climate sensitivity.

Then when we account for the cooling effect of aerosols emitted over the last century responsible for significant solar dimming, radiative forcing thus far would be even lower than 1.2W/m2. Aerosols are estimated to have had a forcing anywhere from -.4W/m2 to -2.4W/m2. Of course we can also through in methane and other human forcings which add to the radiative forcing.

The IPCC estimates total anthropogenic forcing has been between .6 and 2.4W/m2 (best guess 1.2W/m2). Including natural forcing it has been .7-2.5W/m2, best guess 1.7W/m2.

So let's use the 1.7W/m2 total forcing, subtract out the current imbalance of .6W/m2, and get 1.3W/m2.

So 1.3W/m2 has caused .8C of warming over the last century. That would suggest a climate sensitivity of around 2.3C. On the lower end of the IPCC range of 2-4.5C.

[skierinvermont]

Here is the chart I was referring to below.

I actually did the math wrong above. The total forcing that has caused .8C of warming is 1.1W/m2 (best estimate). That would make for a climate sensitivity of 2.7C which is close to the IPCC best estimate of 3C.

1.1W/m2 is the total of natural + anthropogenic minus the current imbalance. But it could be anywhere between .1W/m2 and 1.9W/m2. That would imply a sensitivity of between 1.6C and 30C. Best guess 2.7C as I said above. Obviously >6C can probably be ruled out by other methods.

[blizzard1024]

The constant 5.35 derives from the output of radiative transfer models feed line-by-line transfer codes obtained through the Hitran Database.

Myhre et al.

The 'warming in the pipeline' is represented by the remaining TOA energy imbalance. The surface must radiate at a higher temperature than at present in order to eliminate the current imbalance. The current global average temp balances the total anthropogenic forcing from a time back in the 1980s.

Thanks. Nice paper. I see where they got the 5.35 from. I still don't see the warming in the pipeline...negative feedbacks possibly due to clouds could

have already negated this imbalance. No one can disprove that. Plus, the recent warming until the late 1990s and then the leveling off of the temperature

curve could be totally solar since the sun reached a grand maximum in the late 20th century and now has started to slowly cool. Thus, in my mind, I don't see

why the long term changes in solar radiation from the little ice age maunder minimum to the present could not explain the recent warming. The change in

solar irradiance is estimated to be a net increase of 2.7w/m2 as reconstructed by Lean et al (1995) and Lean (2000). See graph below. Why can't the 2.7W/m2

increase in solar energy be the maindriver of the 20th century warming? This forcing is almost on the order of a doubling of CO2 and I would say is significant.

The little ice age is postulated to be 1 to 1.5C or so cooler than today for a reduction by about 2.7w/m2 of solar energy. (Of course some say the little ice age

was not global so it might be a very small temperature change despite a negative 2.7w/m2 forcing). This would imply strong negative feedbacks. So how can

climate scientists rule out the sun as the main driver of the recent warming? It just defies logic in my mind. Solar irradiance is still around 1366.2 w/m2 but

was postulated to be 1363.5 w/m2 300 to 400 years ago. There has to be lags in the climate system because of the oceans which readily absorb solar

radiation but are not warmed by increased CO2. There are supposedly lags for CO2...then why not the sun? Plus the sun is still putting out more energy

than it was 300 years ago.

I already have seen the work done by climate scientists that show a cooling earth without increasing GHGs from models and then when you increase

GHGs the late 20th century warming appears. This is computer model stuff. I am very skeptical of using models to prove anything especially something

as complex as the climate system.

Lean, J., J. Beer, and R. Bradley. 1995.Reconstruction of Solar Irradiance Since 1610: Implications for Climate Change. Geophysical Research Letters, v.22, No. 23, pp 3195-3198, December 1, 1995.

Lean, J. 2000. Evolution of the Sun's Spectral Irradiance Since the Maunder Minimum. Geophysical Research Letters, Vol. 27, No. 16, pp. 2425-2428, Aug. 15, 2000.

[blizzard1024]

Well I can't answer a couple questions without doing some further reading, but I have two points:

1) I'm not sure where you're getting this -50C from. The atmosphere is constantly emitting in ALL wavelengths. A substance at 15C still is just an average of the kinetic energy of all the particles.. some have much more some have much less.

2) Regarding the proportion of warming thus far that has been anthropogenic I would agree about ~.6C of the total .8C since 1900. However, the earth remains in a large energy imbalance around .6W/m2. Which means that only 1.2W/m2 of the total 1.8W/m2 has taken effect. 1.2W/m2 has caused .6C, which means 3.7W/m2 would cause 1.8C.

That is on the very low end of the climate sensitivity.

Then when we account for the cooling effect of aerosols emitted over the last century responsible for significant solar dimming, radiative forcing thus far would be even lower than 1.2W/m2. Aerosols are estimated to have had a forcing anywhere from -.4W/m2 to -2.4W/m2. Of course we can also through in methane and other human forcings which add to the radiative forcing.

The IPCC estimates total anthropogenic forcing has been between .6 and 2.4W/m2 (best guess 1.2W/m2). Including natural forcing it has been .7-2.5W/m2, best guess 1.7W/m2.

So let's use the 1.7W/m2 total forcing, subtract out the current imbalance of .6W/m2, and get 1.3W/m2.

So 1.3W/m2 has caused .8C of warming over the last century. That would suggest a climate sensitivity of around 2.3C. On the lower end of the IPCC range of 2-4.5C.

The -50C is the temperature at which CO2 radiates most effectively from its 15 micron band from wien's displacement law. Therefore it really only absorbs and

emits radiation most effectively at these very low temperatures. It is transparent to radiation that is warmer because the emission is at smaller wavelengths which are not in the

primary CO2 absorption band of 15 microns. That is why CO2 is most effective in the upper troposphere where it is -50C. Yes all objects emit radiation at all wavelengths but

they maximize their emission depending on temperature assuming they radiate close to a black body. That's wien's displacement law which allows you to correspond a temperature to a wavelength of maximum mission. The end result is that when you increase CO2 you increase the absorption and emission in the upper troposphere which leads to a radiating layer higher up in the atmosphere at colder temperatures and hence less energy escapes, so the atmosphere below warms and cools above the enhanced radiating layer.

[blizzard1024]

Here is the chart I was referring to below.

I actually did the math wrong above. The total forcing that has caused .8C of warming is 1.1W/m2 (best estimate). That would make for a climate sensitivity of 2.7C which is close to the IPCC best estimate of 3C.

1.1W/m2 is the total of natural + anthropogenic minus the current imbalance. But it could be anywhere between .1W/m2 and 1.9W/m2. That would imply a sensitivity of between 1.6C and 30C. Best guess 2.7C as I said above. Obviously >6C can probably be ruled out by other methods.

This often quoted figured shows a radiative forcing of 1.6w/m2 with only .12 w/m2 of forcing from the sun??? I am confused here. First

where are you getting .8C from 1.1 w/m2? How do we know there is an imbalance at all or that warming is not related to the sun? or there

are not negative feedbacks in the system??

[skierinvermont]

This often quoted figured shows a radiative forcing of 1.6w/m2 with only .12 w/m2 of forcing from the sun??? I am confused here. First

where are you getting .8C from 1.1 w/m2? How do we know there is an imbalance at all or that warming is not related to the sun? or there

are not negative feedbacks in the system??

Yes that is right - forcing from the sun is .12W/m2. Not sure what is confusing here. This is a widely quoted figure found in many studies.

A net energy imbalance of the earth is also a widely quoted figure found in many studies. It is derived either by direct measurement of changing OHC, or indirectly by calculating steric sea level rise (sea level rise due to thermal expansion). This energy imbalance represents the additional warming that will occur if CO2 does not rise any further.

Thus the earth experienced a forcing of 1.7W/m2, of which only 1.1W/m2 has taken effect (.6W/m2 'in the pipeline'). Thus .8C of warming has been caused by a forcing of 1.1W/m2, which implies a climate sensitivity of 2.7C. But as I said before, the forcing that has taken effect could be anywhere from .1 to 1.9W/m2. 1.1W/m2 is only a best estimate. We could infer a climate sensitivity anywhere between 1.6C and 30C. Obviously anything above 6C could be ruled out by other methods. And we can probably rule out by similar methods any forcing below .5 or .6W/m2.

[blizzard1024]

Yes that is right - forcing from the sun is .12W/m2. Not sure what is confusing here. This is a widely quoted figure found in many studies.

A net energy imbalance of the earth is also a widely quoted figure found in many studies. It is derived either by direct measurement of changing OHC, or indirectly by calculating steric sea level rise (sea level rise due to thermal expansion). This energy imbalance represents the additional warming that will occur if CO2 does not rise any further.

Thus the earth experienced a forcing of 1.7W/m2, of which only 1.1W/m2 has taken effect (.6W/m2 'in the pipeline'). Thus .8C of warming has been caused by a forcing of 1.1W/m2, which implies a climate sensitivity of 2.7C. But as I said before, the forcing that has taken effect could be anywhere from .1 to 1.9W/m2. 1.1W/m2 is only a best estimate. We could infer a climate sensitivity anywhere between 1.6C and 30C. Obviously anything above 6C could be ruled out by other methods.

Ok. Thanks for your time.

[skierinvermont]

Ok. Thanks for your time.

Another way of thinking of it is that if CO2 increases ceased today we would probably rise another ~.4C over the next 50 years due to the very large energy imbalance that can only be re-balanced by additional warming. Thus total warming would be 1.2C caused by a total forcing of 1.7W/m2 (1.6W/m2 anthro, .12W/m2 solar). That would imply a climate sensitivity of 2.6C per doubling.

Keep in mind estimates of forcing thus far are very uncertain, primarily because of aerosols and also because of clouds. Thus the current temperature record is a pretty poor way of determining climate sensitivity because we don't actually know what forcing has been very well.

[skierinvermont]

Wow solar reconstructions from the 90s? Seriously? These reconstructions have been rejected by everybody in the field. Take a look at some of the newer reconstructions like Leif 2007. Even the deniers at WUWT use these newer reconstructions.

Also I see above you have questioned the existence of an energy imbalance on earth. We know the earth continues to gain massive amounts of heat annually because of direct measurements of OHC, and because sea level continues to rise due to thermal expansion. It is difficult to comprehend the amount of heat being gained but it equates to .6 Joules per second per square meter of the earth. That's .6W/m2.

[blizzard1024]

Wow solar reconstructions from the 90s? Seriously? These reconstructions have been rejected by everybody in the field. Take a look at some of the newer reconstructions like Leif 2007. Even the deniers at WUWT use these newer reconstructions.

Also I see above you have questioned the existence of an energy imbalance on earth. We know the earth continues to gain massive amounts of heat annually because of direct measurements of OHC, and because sea level continues to rise due to thermal expansion. It is difficult to comprehend the amount of heat being gained but it equates to .6 Joules per second per square meter of the earth. That's .6W/m2.

Here are 3 more very recent TSI reconstructions. 2 that have little change as is suggested by the studies you cite and 1 that has a 5.8 w/m2 difference between the Maunder Minimum and the 2008/2009 solar minimum. These images are from Feulner, G. (2011), Are the most recent estimates for Maunder Minimum solar irradiance in agreement with temperature reconstructions?, Geophys. Res. Lett., 38, L16706, doi:10.1029/2011GL048529.

What he does is run climate models to discount the 5.8 w/m2 and side with the very low estimates. If you use the 5.8 w/m2, you get more temperature changes during the little ice age on the order of .5C 50-100 year temperature changes. If you use the lower estimates you get on the order of .2C changes on these time scales. So basically, if you side with the lower estimates you have to believe in 1) the little ice age was only a local Europe phenomena and 2) the climate models do a great job in simulating our current complex climate system.

If we assume 2) is correct, then for several hundred years Europe just was colder and the rest of the planet was warm enough to compensate and thus gave minimal negative anomalies. As a MET I find this very hard to believe. How can one part of the world stay colder than the rest without some major forcing feature like an ice sheet. The circulation of the Earth is well mixed by cyclogenesis that a cold anomaly in one part of the world will get wiped out as the Earth constantly tries to drive the temperature gradient down between the poles and the tropics. So we had an upper level low that spun over Europe for hundreds of years???

Also I love how the author uses aerosols in the 20th century to negate some forcing by GHGs. If this were true then why has the SH which has much less aerosols seen so little warming? The NH has more aerosols and has seen the most warming. I think the sun's role in climate change is being woefully understated. This is not saying increasing CO2 will not lead to warming but I think the Sun has a bigger role in this.

[skierinvermont]

Here are 3 more very recent TSI reconstructions. 2 that have little change as is suggested by the studies you cite and 1 that has a 5.8 w/m2 difference between the Maunder Minimum and the 2008/2009 solar minimum. These images are from Feulner, G. (2011), Are the most recent estimates for Maunder Minimum solar irradiance in agreement with temperature reconstructions?, Geophys. Res. Lett., 38, L16706, doi:10.1029/2011GL048529.

What he does is run climate models to discount the 5.8 w/m2 and side with the very low estimates. If you use the 5.8 w/m2, you get more temperature changes during the little ice age on the order of .5C 50-100 year temperature changes. If you use the lower estimates you get on the order of .2C changes on these time scales. So basically, if you side with the lower estimates you have to believe in 1) the little ice age was only a local Europe phenomena and 2) the climate models do a great job in simulating our current complex climate system.

If we assume 2) is correct, then for several hundred years Europe just was colder and the rest of the planet was warm enough to compensate and thus gave minimal negative anomalies. As a MET I find this very hard to believe. How can one part of the world stay colder than the rest without some major forcing feature like an ice sheet. The circulation of the Earth is well mixed by cyclogenesis that a cold anomaly in one part of the world will get wiped out as the Earth constantly tries to drive the temperature gradient down between the poles and the tropics. So we had an upper level low that spun over Europe for hundreds of years???

Also I love how the author uses aerosols in the 20th century to negate some forcing by GHGs. If this were true then why has the SH which has much less aerosols seen so little warming? The NH has more aerosols and has seen the most warming. I think the sun's role in climate change is being woefully understated. This is not saying increasing CO2 will not lead to warming but I think the Sun has a bigger role in this.

Aerosols are actually fairly well distributed globally IIRC. You can check that if you like. The SH also is much more ocean which warms slower.

Regarding solar reconstructions, I'm not familiar with the one you are citing showing 5.8W/m2. But you are the one using climate models to assume 5.8W/m2. The reconstructions showing a much smaller variability are derived directly from sunspot numbers and understanding of solar processes. They have nothing to do with climate models. I think if you look into this further, you will find the old reconstructions are completely rejected.

Which makes sense... solar activity even in deep solar minimums has never been observed to deviate below a certain level.

[blizzard1024]

Aerosols are actually fairly well distributed globally IIRC. You can check that if you like. The SH also is much more ocean which warms slower.

Regarding solar reconstructions, I'm not familiar with the one you are citing showing 5.8W/m2. But you are the one using climate models to assume 5.8W/m2. The reconstructions showing a much smaller variability are derived directly from sunspot numbers and understanding of solar processes. They have nothing to do with climate models. I think if you look into this further, you will find the old reconstructions are completely rejected.

Which makes sense... solar activity even in deep solar minimums has never been observed to deviate below a certain level.

How do you explain the little ice age? It is just a coincidence it occurred with a deep solar minimum where little or no sunspots were observed. Something just does not add up in my mind that solar forcing is weak. I think it is understated. My opinion. That's all. That is not to say that CO2 increases will not warm the earth. yes I know the SH has more water and slower response. What are your references that aerosols are well mixed both hemispheres? I thought they had a short residence time in the atmosphere because they rain out? Don't they? please provide some references. I will look for some on the aerosol issue too.... thanks.

[WeatherRusty]

If we accept a TSI increase of 2.7W/m^2 since about 1750, this is in line with the generally accepted 0.1% increase in solar irradiance since the depth of the Maunder Minimum and also over the course of a full 11 year sunspot cycle.

The change in TSI is not a radiative forcing however. To determine radiative forcing we divide TSI by 4 to account for the geometry of the Earth, and multiply by 0.7 to account for the Earth's albedo. Then we must realize that only a portion of the total EM wavelengths warm the surface. Altogether this gets us in the 0.6 to 0.30W/m^2 range (0.12W/m^2 best IPCC estimate) for solar radiative forcing.

Since the Planck response (before feedback) is 0.3C per watt, we get a warming of less than 0.1C from this degree of forcing .

[blizzard1024]

If we accept a TSI increase of 2.7W/m^2 since about 1750, this is in line with the generally accepted 0.1% increase in solar irradiance since the depth of the Maunder Minimum and also over the course of a full 11 year sunspot cycle.

The change in TSI is not a radiative forcing however. To determine radiative forcing we divide TSI by 4 to account for the geometry of the Earth, and multiply by 0.7 to account for the Earth's albedo. Then we must realize that only a portion of the total EM wavelengths warm the surface. Altogether this gets us in the 0.6 to 0.30W/m^2 range (0.12W/m^2 best IPCC estimate) for solar radiative forcing.

Since the Planck response (before feedback) is 0.3C per watt, we get a warming of less than 0.1C from this degree of forcing .

This makes a lot of sense. Thank you. I forgot about the geometry arguments and of course albedo. I have read (not sure where) that the warming up until

1940 or so was likely solar related...is this really true without any feedbacks? What caused the warming before 1940? There must be some feedbacks that

amplify the solar forcing. I am NOT going to the cosmic ray stuff...please don't hammer me on this. This is an area which probably needs more research and

for now is not proven from what I have read.

Do you all believe the little ice age was mainly a european phenomena? I have a hard time believing this. Just an opinion here.

[skierinvermont]

How do you explain the little ice age? It is just a coincidence it occurred with a deep solar minimum where little or no sunspots were observed. Something just does not add up in my mind that solar forcing is weak. I think it is understated. My opinion. That's all. That is not to say that CO2 increases will not warm the earth. yes I know the SH has more water and slower response. What are your references that aerosols are well mixed both hemispheres? I thought they had a short residence time in the atmosphere because they rain out? Don't they? please provide some references. I will look for some on the aerosol issue too.... thanks.

I prefer a mean of the various global reconstructions. It was a global phenomenon, but it was stronger in Europe which makes sense given there is also evidence of a abnormally persistent -NAO.

The mean shows a cooling from the MWP to LIA of .5C, which is fairly well explained by solar forcing of maybe -.2 or -.3W/m2, and increased volcanic activity during the LIA. People often forget the increased volcanic activity during the LIA and the profound effect volcanoes have on climate.

Also remember the forcing of .12W/m2 in the IPCC report is from 1750 to present. The mid 1700s actually had pretty high solar activity (though not as high as the late 20th century). Forcing from the Maunder minimum to present is probably over twice that, close to .3W/m2.

Again it just makes no sense that TSI would drop more than 1.5W/m2 - all solar minimums that we have observed since 1970 have the exact same TSI. It never drops below that value even when there are no sunspots (see for example the very deep and long solar minimum of the last 5+ years). Only the strength of the maximums change.

I'll get back to you about aerosols being moderately well mixed. They are short lived, but it still allows enough time for some mixing. That, combined with the higher ocean %, strengthening AAO, and less change in surface albedo may explain the slightly slower warming.

[blizzard1024]

I prefer a mean of the various global reconstructions. It was a global phenomenon, but it was stronger in Europe which makes sense given there is also evidence of a abnormally persistent -NAO.

The mean shows a cooling from the MWP to LIA of .5C, which is fairly well explained by solar forcing of maybe -.2 or -.3W/m2, and increased volcanic activity during the LIA. People often forget the increased volcanic activity during the LIA and the profound effect volcanoes have on climate.

Also remember the forcing of .12W/m2 in the IPCC report is from 1750 to present. The mid 1700s actually had pretty high solar activity (though not as high as the late 20th century). Forcing from the Maunder minimum to present is probably over twice that, close to .3W/m2.

Again it just makes no sense that TSI would drop more than 1.5W/m2 - all solar minimums that we have observed since 1970 have the exact same TSI. It never drops below that value even when there are no sunspots (see for example the very deep and long solar minimum of the last 5+ years). Only the strength of the maximums change.

I'll get back to you about aerosols being moderately well mixed. They are short lived, but it still allows enough time for some mixing. That, combined with the higher ocean %, strengthening AAO, and less change in surface albedo may explain the slightly slower warming.

Yes I can see a persistent negative NAO/negative AO leading to cooler conditions in the winter especially, which would sway the global mean down given the NH landmasses.

The tropics are a huge "store" of energy and damp out such negative swings. Volcanic activity was high back then yes I see that...but has been lacking lately since 1992, so I assume some of the warming we have seen since the early 1990s could be attributed to lack of volcanic activity?? On another note, is the massive coal burning in China and India leading to more aerosols and possibly a reason why global temperatures have leveled off just like when the U.S was burning coal away back in the 40s, 50s, 60s and 70s?

Basically, the only area that I am questioning is the climate sensitivity of doubled CO2 and the role of natural variability basically from the Sun. Unless you invoke some unknown amplifier for the changing TSI, it looks to indeed be small. The geometry argument from WeatherRusty was convincing. In addition, albedo especially from low clouds has to be uncertain too. I wish there was a reliable dataset that showed extent of cloud cover and changes over the past 50-60 years. This is another area of tremendous uncertainty. To me the science is far from settled and I think you would agree with me. I think AGW from increased CO2 is a settled science. The feedbacks are not known well enough in my opinion for CAGW. Hence I am skeptical of CAGW....not AGW. Remember that. I am skeptical of a lot of complex scientific theories so climate change is just one of many. It is how I learn. Thanks for your willingness to participate.

[skierinvermont]

Yes I can see a persistent negative NAO/negative AO leading to cooler conditions in the winter especially, which would sway the global mean down given the NH landmasses.

The tropics are a huge "store" of energy and damp out such negative swings. Volcanic activity was high back then yes I see that...but has been lacking lately since 1992, so I assume some of the warming we have seen since the early 1990s could be attributed to lack of volcanic activity?? On another note, is the massive coal burning in China and India leading to more aerosols and possibly a reason why global temperatures have leveled off just like when the U.S was burning coal away back in the 40s, 50s, 60s and 70s?

Basically, the only area that I am questioning is the climate sensitivity of doubled CO2 and the role of natural variability basically from the Sun. Unless you invoke some unknown amplifier for the changing TSI, it looks to indeed be small. The geometry argument from WeatherRusty was convincing. In addition, albedo especially from low clouds has to be uncertain too. I wish there was a reliable dataset that showed extent of cloud cover and changes over the past 50-60 years. This is another area of tremendous uncertainty. To me the science is far from settled and I think you would agree with me. I think AGW from increased CO2 is a settled science. The feedbacks are not known well enough in my opinion for CAGW. Hence I am skeptical of CAGW....not AGW. Remember that. I am skeptical of a lot of complex scientific theories so climate change is just one of many. It is how I learn. Thanks for your willingness to participate.

I have read that the low volcanic activity of the 20th century is believed to have contributed slightly to warming especially the warming in the 30s and 40s. The late 20th century has seen near-average volcanic acitivity I would guess, maybe a bit on the low side still. (A couple big ones in the 60s, El Chichon in 1982, and Pinatubo in 1991).

Yes I was just reading the abstract of a paper yesterday that said increased aerosol emissions the last 10 years have had a slowing effect on warming (by exerting a negative forcing). After leveling off and even declining slightly since 1975, the 2000s have seen the first increase in aerosol emissions (albeit a moderate one). SkS links to a couple studies suggesting east asian aerosols have a stronger cooling effect than NA or European aerosols because they get lofted into the upper atmosphere more and have a longer lifespan. They also say that the lifespan is from a couple weeks to a few years. They postulate that aerosols (in addition to the solar minimum and increased frequency of La Ninas) have been responsible for the reduced warming trend (~.1-.12C/decade vs nearly .2C/decade in the 80s and 90s).

http://www.skeptical...ot-Hotter-.html

I agree that a lower climate sensitivity of 2C cannot be ruled out, but neither can a higher climate sensitivity of 4.5C. Personally I think the evidence points more to a lower climate sensitivity between 2-3C, but the higher sensitivities cannot be ruled out.

[blizzard1024]

I have read that the low volcanic activity of the 20th century is believed to have contributed slightly to warming especially the warming in the 30s and 40s. The late 20th century has seen near-average volcanic acitivity I would guess, maybe a bit on the low side still. (A couple big ones in the 60s, El Chichon in 1982, and Pinatubo in 1991).

Yes I was just reading the abstract of a paper yesterday that said increased aerosol emissions the last 10 years have had a slowing effect on warming (by exerting a negative forcing). After leveling off and even declining slightly since 1975, the 2000s have seen the first increase in aerosol emissions (albeit a moderate one). SkS links to a couple studies suggesting east asian aerosols have a stronger cooling effect than NA or European aerosols because they get lofted into the upper atmosphere more and have a longer lifespan. They also say that the lifespan is from a couple weeks to a few years. They postulate that aerosols (in addition to the solar minimum and increased frequency of La Ninas) have been responsible for the reduced warming trend (~.1-.12C/decade vs nearly .2C/decade in the 80s and 90s).

http://www.skeptical...ot-Hotter-.html

I agree that a lower climate sensitivity of 2C cannot be ruled out, but neither can a higher climate sensitivity of 4.5C. Personally I think the evidence points more to a lower climate sensitivity between 2-3C, but the higher sensitivities cannot be ruled out.

This is very interesting. The East Asian's will continue to ramp up their aerosol emissions at least in the near term. I wonder if this will temporarily halt or even reverse global warming like the period of the 1940s to 1970s...especially since they are higher up and last longer. are there any estimates of when they will peak in east asia?? This could be a problem down the road...what will win? CO2 or SO2??? Of course there was less CO2 in the 1940-1970 time frame when compared to today....interesting stuff. Thanks.

[skierinvermont]

This is very interesting. The East Asian's will continue to ramp up their aerosol emissions at least in the near term. I wonder if this will temporarily halt or even reverse global warming like the period of the 1940s to 1970s...especially since they are higher up and last longer. are there any estimates of when they will peak in east asia?? This could be a problem down the road...what will win? CO2 or SO2??? Of course there was less CO2 in the 1940-1970 time frame when compared to today....interesting stuff. Thanks.

I would guess that East Asia will start slowing their emissions growth over the next decade or two. There has been increasing unrest about environmental concerns. They are becoming wealthier and will begin to transition to more of a service based economy. They will be able to afford pollution control more. And finally, economic growth in East Asia is beginning to slow. It's unlikely China will continue to see 10% GDP growth as they did over the last two decades of extraordinary growth. They will continue to grow quickly but maybe at 6 or 7% instead of 10%. That's a big difference over 10 years.

1.07^10 = 2

1.10^10 = 2.6

[WeatherRusty]

This makes a lot of sense. Thank you. I forgot about the geometry arguments and of course albedo. I have read (not sure where) that the warming up until

1940 or so was likely solar related...is this really true without any feedbacks? What caused the warming before 1940? There must be some feedbacks that

amplify the solar forcing. I am NOT going to the cosmic ray stuff...please don't hammer me on this. This is an area which probably needs more research and

for now is not proven from what I have read.

Do you all believe the little ice age was mainly a european phenomena? I have a hard time believing this. Just an opinion here.

Yes, in the real world there will be feedback to the Planck response. If we allow for a climate sensitivity which approximately doubles the Planck response, say from increased water vapor alone, and the Planck response to solar has produced a 0.08C warming, we can see how something close to 0.16C of total warming might be attributable to solar variability since 1750.. You will find estimates of warming attributable to solar in the 10-20% range if you look around. This solar warming influence (TSI) has not been a factor during the past several decades of warming however.

[skierinvermont]

Yes, in the real world there will be feedback to the Planck response. If we allow for a climate sensitivity which approximately doubles the Planck response, say from increased water vapor alone, and the Planck response to solar has produced a 0.8C warming, we can see how something close to 1.6C of total warming might be attributable to solar variability since 1750.. You will find estimates of warming attributable to solar in the 10-20% range if you look around. This solar warming influence (TSI) has not been a factor during the past several decades of warming however.

Where do you get a solar Planck response since 1750 of .8C from? At most I see .2 or .3W/m2 which would be a Planck response of .1C. Double that for approximate feedbacks and you get .2C.

And that's from the Maunder minimum of the 1600s, not 1750 which had solar activity much closer to today's (hence the IPCC .12W/m2).

You're seriously deviating from the IPCC's .12W/m2 to suggest .8C... that would be nearly 2W/m2. Nearly 2000% of the IPCC estimate.

[WeatherRusty]

Warming and cooling is never uniformly distributed globally. It just might be the the coolest climate during LIA set up over Europe and Asia even if the event was global, which to a degree it most likely was. However, the global average temperature was no more than 1C cooler than today at most, according to my understanding.

[skierinvermont]

Warming and cooling is never uniformly distributed globally. It just might be the the coolest climate during LIA set up over Europe and Asia even if the event was global, which to a degree it most likely was. However, the global average temperature was no more than 1C cooler than today at most, according to my understanding.

Yes 1C would be on the high side, .6 or .7C looks to be the mean cooling from MWP to LIA. As I suggest above .2C, maybe .3C of that was solar.

[WeatherRusty]

Where do you get a solar Planck response since 1750 of .8C from? At most I see .2 or .3W/m2 which would be a Planck response of .1C. Double that for approximate feedbacks and you get .2C.

And that's from the Maunder minimum of the 1600s, not 1750 which had solar activity much closer to today's (hence the IPCC .12W/m2).

You're seriously deviating from the IPCC's .12W/m2 to suggest .8C... that would be nearly 2W/m2. Nearly 2000% of the IPCC estimate.

Sorry skier, thanks for the heads up. That was a stupid mistake. It should be 0.08C........

[skierinvermont]

Sorry skier, thanks for the heads up. That was a stupid mistake. It should be 0.08C........

Yeah that make way more sense and even that is more representative of Maunder to present than 1750 to present.

I was getting .1C Maunder to present and maybe half that for 1750 to present for Planck response.

2 or 3X that for feedbacks. .2-.3C Maunder-present and .1-.15C 1750-present respectively.

[WeatherRusty]

Yeah that make way more sense and even that is more representative of Maunder to present than 1750 to present.

The IPCC at one time regarded solar forcing to be near 0.24W/m^2, since revised to 0.12W. I am being generous with the 0.08C Planck response as it reflects the older estimate for forcing, but still within the range of uncertainty.

[skierinvermont]

The IPCC at one time regarded solar forcing to be near 0.24W/m^2, since revised to 0.12W. I am being generous with the 0.08C Planck response as it reflects the older estimate for forcing, but still within the range of uncertainty.

The new draft report uses .04W/m2 for 1750-2011 but I'm not sure if that reflects a change in understanding or simply the weaker recent solar cycle.

[csnavywx]

This is very interesting. The East Asian's will continue to ramp up their aerosol emissions at least in the near term. I wonder if this will temporarily halt or even reverse global warming like the period of the 1940s to 1970s...especially since they are higher up and last longer. are there any estimates of when they will peak in east asia?? This could be a problem down the road...what will win? CO2 or SO2??? Of course there was less CO2 in the 1940-1970 time frame when compared to today....interesting stuff. Thanks.

China started installing SO2 scrubbers in 2006 and 2007, which seems to have had the effect of reversing the trend of SO2 emissions from China lately. It's unknown when full compliance will take hold. India on the other hand, has not implemented this kind of program (as far as I can tell). Either way, the level of SO2 is still definitely higher than it was in the late 90s and early 2000s, but it does not seem to be increasing like it was from 1998-2006. This makes sense, since Chinese coal consumption tripled since 1998 (and the world about double).

As a personal anecdote, the "Asian Brown Cloud" was something I had to deal with frequently with forecasting flights around Asia. It's thick, nasty and reduces sunlight substantially, especially through cloud and widespread smog formation. The effects are mostly regional, but regional forcing can easily reach -20 to -30 w/m2 (not a typo). It's understandably more diffuse as it spreads out and is affected by natural precipitation scrubbing, but some of that pollution spreads out over a much larger area and the indirect effect on clouds seems substantial. We use global averages for this forcing, but it is typically very regionally concentrated and irregular.

In the end, SO2 vs CO2 is a Faustian bargain, because SO2 aerosols have a lifetime of days to weeks (on average), whilst CO2 emissions last decades to millennia. The irony is that while we try to clean up SO2 (for good reasons), it "unmasks" CO2's forcing. That's the big worry in climate sensitivity research. If that negative forcing number from aerosols happens to be fairly high (say -1.6 or more), then this implies a very large climate sensitivity (>4C) almost no matter which way you dice it. The lower sensitivities all require values on the very optimistic side of the forcing uncertainty ranges for aerosols. At the moment, it appears possible, but not likely. You'll notice the long, fat tail towards the high range of estimates. The central 3C estimate is bad enough, anything past 4C (a "tail event") is disastrous. Much higher values (>6C) can't be ruled out, but I think Hansen's argument from paleoclimate shunts those extreme values off to "unlikely".