Low activity because...
For the few who were wondering about the low activity and slow response to comments... I am busy this semester with teaching two courses, one of which is new (on fluid mechanics), so between preparing clear class notes and trying to continue research, my sciencebits.com response time has slowed down. Rest assure, it is only temporary.
Comments (5)
I made a comment more that two months ago about the problem I have with solar explanations for recent warming, given that the change in solar activity since 1950 is much less that the change over 1900-1950. Thus if solar factors are important in recent warming we should have seen MUCH more warming (like over a degree) in the early 20th century.
Since then I have put together a simple model that nonphysicists like myself can understand that does a pretty good job of explaining temperature movements over the last 150 years as well as a number of other things like why a Venus-like "runaway greenhouse effect" cannot happen to the Earth in its current orbit, but if the Earth were moved to Venus's orbit it would eventually become like Venus.
I'm looking for comments, as my grasp of these things is not complete by a long shot. The address is in my sig line.
Thanks
Simple Global Warming Model
http://my.net-link.net/~malexan/Climate-Model.htm
Sorry for not writing more before. I am still under a ton of work.
The so called problem with the temperature rise over the past 2.5 decades compared with the temperature rise in the first half of the 20th century is not really a problem if you consider the fact that it takes time for the oceans to warm. Basically, the we are now paying for a rise because over the past several decades (from the middle of the 20th century) the activity was high, so even though the rise from the 80's till today in solar activity is most likely smaller than the rise from 1910 to 1940, the long term increase in solar activity contributes a lot to the warming.
Be rest assure that once I have time to write a deep thorough analysis to this question, I will do so. I'll take a look on your site. Cheers.
Nir
I don't think oceanic lag can explain the temperature rise. About half of the CO2 added to the atmopshere since 1950 is still there, so only about half has been removed--mostly absorbed by the oceans. The solubility of CO2 in seawater is roughly directly proportional atmospheric CO2. The proportionality constant is a function of pH and very weakly temperature. If you plot total CO2 removed against CO2 solubility you get a nice straight line the slope of which is the volume of seawater available to dissolve the missing CO2. The value obtained amounts to a surface layer 125 meters thick. Whether you incorporate pH into the solubility or leave it out gives you essentially the same 125 meter absorption depth (within 1 meter).
So the Earth's oceans have acted as a "CO2 sponge" over the last half century that is about 125 meters thick. We know the "sponge" cannot be much thicker than 125 meters or more CO2 would have been absorbed and CO2 levels in the atmosphere would be much lower. We can say the same about much thinner sponges.
Now this 125 meter CO2 sponge can also act as a heat sink. If I impose an 11 year cyclical forcing of size F on this sink I will get a temperature response that decays to a "steady state" cyclical response around F/2 whose magnitude is smaller than what one would calculate assuming no lag (i.e. lambda * F).
The transients have a time constant of 4.5 years so they are fully relaxed in 15-20 years. From the magnitude of the cyclical response one can obtain a damping factor that can be used to estimate the size of the solar forcing from the 11-year solar cycle. My value falls into the same range as the ones you used.
Since my damping values are similar to those you used and the CO2 behavior has been what it was, this strongly indicates that the 15-20 year relaxation time is right. That is, a step or ramp change in forcing that was complete in the 1950's would be fully incorporated into the global temperature by around 1970, assuming that the oceanic surface waters were the dominant heat sink in the post-1950 period just as it was the dominant CO2 sink over the same period.
In other words, it is highly unlikely that changes in temperature in the post-1970 period are reflecting changes in solar forcing from the 1950's and before.
With this the only way to make solar effects relevant to recent warming would be to increase the size of the forcing produce by a change in solar activity. But then the increase in temperature in the early 20th century would be far too small to be consistent with the change in solar activity then.
If you use the 125 m thick surface ocean as your principal sink you predict a temperature rise of about 0.3-0.4 C from solar factors over the 1900-1950 period compared to about 0.1 C from greenhouse gases.
For the recent warming there is essentially no net increase in solar forcing since the 1950's, but there is plenty of greenhouse forcing. Not only that, but the drop in solar activity from the 1950's to 1970's coupled with rising aerosols easily overwhelms the greenhouse effect over this time, explaining why temeprature fell somewhat over these decades. Then when solar activity recovers and aerosol output levels off in the 1990's the greenhouse signal can come through, nicely explaining the recent warming.
Simple Global Warming Model
http://my.net-link.net/~malexan/Climate-Model.htm
I made an error in my calculation of CO2 solubility. I not longer can obtain a value for surface waters depth using this approach and my conclusions about ocean lags are not valid. I am attempting to rectify the problem but am having difficulty with the solubility issue. The key issue is that CO2 is less soluble at lower pH but is more soluble with higher atmospheric CO2 levels. Oceanic pH has fallen due to higher atmospheric CO2. I can model this pH effect and get a 0.1 unit drop since the beginning of industrialization, which is what I read in the web literature on this topic. But such a pH drop means that overall CO2 solubility as calculated in my more complex, but still simple solubility model has fallen slightly. In other words no CO2 has been absorbed by the oceans, which is clearly wrong, about half has been.
So this is a difficult question and I will be wrestling with it. Anyways I have no way to get a value for L at present using a simple analysis. My mass-transfer analogy strategy is a bust as of now.
Simple Global Warming Model
http://my.net-link.net/~malexan/Climate-Model.htm
I fixed the problem I had with my calculation of CO2 solubility in seawater. I didn't have a solubility product for CaCO3 in seawater, just the value for water. I found a value and it is much higher in seawater. With this I was able to easily calculate CO2 solubility in seawater and obtain pH effects consistent with those reported in the literature. I was also able to use them to estimate the thickness of the well-mixed ocean layer at 300 meters.
With this depth the first-order time constant of the land-ocean system using simple models is about 7.5-11 years. This means that the 90% response to a *step* forcing increase wuld be about 17-25 years. But to a *ramp* increase like the increase in solar forcing over a 40 year period early in the 20th century the 90% response occurs 5.5-7.5 years after the ramp ends.
For pre-1960 solar activity changes to still have an impact today implies a well-mixed surface layer approaching two kilometers in depth, which isn't realistic. There would be *much* less CO2 in the atmosphere today if such a great depth of seawater were available to exchange CO2 (and heat) with the atmosphere. This means the absence of a net increase in solar-mediated forcing over the past 30 years is a powerful and serious argument against any significant involvement of solar activity in post-1975 warming.
Simple Global Warming Model
http://my.net-link.net/~malexan/Climate-Model.htm