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Discussion 5 to Meditation 816
More on Warming

by: Clay Chesney

To add to this exchange of views (or any other,) please use the Contact form. This discussion has been continued.

Below I have reproduced a graph from the Intergovernmental Panel on Climate Change (IPCC) report showing the results of climate modeling for the period from about 1860 to 2008.  The observed temperatures are in red, while simulations by four different computer models are shown as black lines.  Readers can decide for themselves if the computer simulations in the graph match the actual temperatures “fairly well” as I said in my last post. 

Observed temperature and modelled temperatures 1850 - 2000

Different models produce somewhat different results, but the IPCC report says that all the models it has examined are “unanimous in their prediction of substantial climate warming under greenhouse gas increases, and this warming is of a magnitude consistent with independent estimates derived from other sources, such as from observed climate changes and past climate reconstructions.” 

I will address my other comments to Gordon Barker, as we seem to have moved to the first person level. 

Computer modeling is not used to predict climate for the past 14,000 years because it depends on data about solar and atmospheric events that have been recorded only for recent times.  More importantly, computer climate models are not intended to forecast for unlimited time ranges.    At this point, the models are calibrated for a range of conditions and known “forcings” that should yield reasonable approximations in the range of a few hundred years.  The special value in modeling is in predicting the effects of increased greenhouse gases that can add significant heat to the atmosphere in a relatively short time span.  

Your newspaper citation (which begins with hyperbole, includes the fiction that there was a decade–long halt in global warming since 1998, and doesn’t name the “top scientific journals”) says that there might be less CO2 added to the atmosphere.  I’m sure one of the articles appeared in Science Magazine, authored by Solomon, et al.  The change in water vapor was temporary, the effect was small, and it has started to rise again. You can read about it here: http://www.sciencemag.org/cgi/content/abstract/science.1182488

Water vapor is a dominant greenhouse gas contributing to warming and its role is no mystery.  As temperature rises, its concentration increases due to evaporation, so its major effect in climate change is to multiply the impact of temperature increases caused by carbon dioxide and other greenhouse gases. Your assertion that water vapor is not included in computer climate models is untrue. Even James Hansen’s pioneering model from 1988 included water vapor, as can be seen in the peer-reviewed paper: http://pubs.giss.nasa.gov/docs/1988/1988_Hansen_etal.pdf

I would like for you to tell me exactly where, in the IPCC report it says that the “medieval warming period” did not exist.  What it said is that even though there were areas that had much higher than normal temperatures for that period, the average global temperature was still lower than it is today. 

Your newspaper article does say, and I assume you agree, that carbon dioxide is an agent that causes global warming.  And that is the point here. 

This is an issue of basic physical science.  Carbon dioxide, as can be easily demonstrated in the lab, does not absorb much energy as sunlight moves through it, but is a strong absorber of infrared radiation (heat).  The earth’s surface, heated by the sun, will radiate heat back to space but carbon dioxide absorbs much of that infrared, resulting in a warmer atmosphere.  The larger the percentage of carbon dioxide, the warmer the atmosphere will be. The amount of atmospheric heating that results can be calculated based on the heat absorption capacity of the gas and its concentration in the atmosphere. Human activities are putting a lot of carbon dioxide into the atmosphere.  The effect of our additions is multiplied because a small temperature rise will warm the oceans, which causes additional dissolved carbon dioxide to be released from the water.  This can be calculated also. 

The whole system is not nearly as complicated as you envision.  The sun is the only significant source of heat for the atmosphere.  Changes in climate are caused by (1) changing the incoming solar radiation (e.g., by changes in the Earth’s orbit or in the Sun itself), (2) changing the fraction of solar radiation that is reflected (this fraction is called the albedo – it can be changed, for example, by changes in cloud cover, small particles called aerosols or land cover), and (3) altering the long wave energy radiated back to space (e.g., by changes in greenhouse gas concentrations).  A good description, plus explanations for climate changes before the industrial era can be found at:


The recent increases in average global temperatures have come at a time when the amount of sunlight is decreasing, as shown in the graph below.  The only good answer for this anomaly is the increase of carbon dioxide and a few other anthropogenic gases of the atmosphere.

Temperature vs Solar Activity 1880-2010

Chart from:  http://www.skepticalscience.com/solar-activity-sunspots-global-warming.htm

Carbon dioxide is now higher than it has been for at least two million years as measured by Arctic ice cores.  During the past 650,000 years, CO2 concentration varied between a low of 180 ppm during cold glacial times and a high of 300 ppm during warm interglacials. Over the past century, it rapidly increased well out of this range, and is now 379 ppm (see Chapter 2). For comparison, the approximately 80-ppm rise in CO2 concentration at the end of the past ice ages generally took over 5,000 years.

“Earth is now absorbing 0.85 ± 0.15 W/m2 more energy from the Sun than it is emitting to space. This imbalance is confirmed by precise measurements of increasing ocean heat content over the past 10 years.”  Statement from:


So, a few parting thoughts:

We are adding a gas that traps heat to the atmosphere.  How, then, does that not cause atmospheric heating?

You say that climate is driven by thousands of factors that we don’t understand.  How do you know they have significant effects if you do not understand them?  You have named only three; can you provide a list?  Can you provide a description of how they affect climate, the relative magnitude of that effect and a few peer reviewed publications about them with the kind of proof you are demanding for anthropogenic global warming?   

You say there are no peer-reviewed articles on global warming, but in fact they number in the hundreds if not the thousands, and can be found in publications of the National Academy of Sciences, Science Magazine, Proceedings of the Royal Society, and NASA, to name a few.   What is lacking are peer-reviewed articles that take the position you are advocating.

Mars is warming because dust storms have uncovered large areas of dark rocks that absorb more sunlight than the sand that formerly covered them.  You really should do a little more reading.