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The idea that global warming is caused by changes in solar output rather than human activity has been dealt a further blow by a new analysis of temperature, volcanic and solar-radiation data by a physicist in Germany. The research, carried out by Pablo Verdes from the Heidelberg Academy of Sciences in Germany, does not rely on climate models, which cannot account for all global-warming mechanisms. Instead, the work reveals a strong statistical link between rising temperatures and greenhouse gas emissions (Phys. Rev. Lett. 99 048501).

Most of the evidence for human-induced or “anthropogenic” climate change has come from climate models, which simulate the dynamics of the atmosphere using complex fluid-flow equations. Given inputs of temperature and other climate data from instruments and older proxy records, such as tree rings, these equations are solved numerically using short time increments.

Although all climate models indicate that the Earth’s temperature will continue to rise, some climate-change sceptics have suggested that the anthropogenic influences are exaggerated. For example, because the simulations divide the atmosphere into a 3D lattice with a coarse resolution, they cannot take into account the effects of clouds, which can both reduce or enhance warming.


Rather than trying to simulate the atmosphere as climate models do, Verdes has used statistics to assess man’s role in climate change.

Verdes started with data records of the past 150 years of the three main natural components thought to be involved in global warming: temperature anomalies, volcanic activity and the energy received from the Sun. To see if these were the only significant components, he looked for trends between the data - that is, if changes in volcanic activity and solar output could account for the changes in temperature. Verdes then checked whether the addition of an external driving force, such as human activity, resulted in a better description of the data.


To do this Verdes used a theory known as nonlinear time-series analysis, whereby the existence of a slowly-varying driving force can be deduced without any knowledge of internal dynamics. First, he assumed the driving force was zero and chose a generic function to fit the data computationally. He then introduced a non-zero driving force and estimated different profiles that would improve the accuracy of the fit.

Verdes found that the driving-force profile that produced the best fit almost exactly matched records of greenhouse gas and aerosol emissions (see Driving force). In other words, fitting the data using the natural components alone left a hole that could be filled by our anthropogenic components. “The coincidence is remarkable,” he said.

The results add weight to the consensus of the Intergovernmental Panel on Climate Change, which came to the conclusion earlier this year that humans are to blame for rising temperatures.

Verdes thinks that his statistical approach should “enrich the continuing debate on the future of our climate.”

The main question is how much of that 15 degrees K is caused by water vapor and natural CO2 versus man made CO2. To look at it another way, the different gases in the atmosphere at any given instant are holding that much energy, which in turn causes a certain amount temperature increase. You cannot only consider the radiative part of the equation when trying to figure out how much each gas contributes to the total of 15 K. There are also all those water molecules that are holding energy and are “excited” and are exchanging energy back and fourth by collision as the air mass they are in moves about. This includes the water in the clouds as well as the water vapor in the air below the clouds. Clouds slow down convection, this causes the air mass below to slow down the escape of energy back into space and therefore increase the greenhouse effect. This is separate from the radiative calculations. I’ll leave it up to those with more physics experience and education to calculate all that.

There are also questions about density that need to be answered. Saying that CO2 is 383 ppm can be misleading. CO2 may be 380 ppm in a cubic meter of air that is much more dense at the surface than say at 18,000 feet, but the total number of molecules will be much less than at 18,000 feet, while it is still 380ppm.

That said I would also mention that many of the IPCC calculations are made using computer models that still need work. Of course there is another problem that has arisen in the past two months, the temperature stations. AGW supporters have pointed to the results of the temperature stations to confirm the calculations made by their computer models. Now we have learned that these stations have many problems that have resulted in warm biases.

Some people might say that I am jumping to conclusions when I say that the surface temperature record is invalid but they do not know what I know. To date, much of the discussion on the temperature stations has focused on blacktop, air conditioners, roofs, burn barrels and etc. Anthony Watts and his volunteers at Surfacestations.org noticed that humans are moving closer to the temperature stations and that the temperature stations are moving closer to humans. Anthony is also conducting experiments on weather or not the paint is causing a warm bias. But what has not been discussed much is the problem of the wind and how there needs to be a good distance from buildings and trees to ensure proper mixing. Otherwise the thermometer just sits there and cooks. This brings about another problem that KBSF volunteers have learned; the biological problem. It seems that wasps like to build their nests in these instruments. Also, after the instruments are installed, trees and bushes often grow around the stations causing problems with the wind.

Not only has KBSF pretty much surveyed every active station in New England, we have also spoken to some of the guys that work for NWS who actually install and calibrate the temperature stations. These guys have a lot to offer. They all say they do the best they can with what they have. They are limited by government budgets. They have to compromise with the owners of the properties where the stations are located so stations are often moved closer to structures for “convenience.” They talk about the constant changing of equipment and locations. When a property is sold and the new owner does not want to take part in the program, they have to find a new location in the neighborhood or close the historical station. They confirm that the problem is widespread. I understand that NWS personnel should maintain the instruments once or twice a year and that there is a record of each visit to the site. I am sure that these guys and their records will eventually be given more consideration by the scientists who publish surface temperature records. But what is most painfully obvious is that these stations are there to record the weather and not make the kind of scientific observations that are expected when studying climate. No one cares if the temperature that day will be 73 F or 74.5 F, but it makes a difference when the amount of global warming over 100 years is less than that amount.