It is well known in the scientific literature that the computer models being used by the U.N.’s Intergovernmental Panel on Climate Change (IPCC) have done a miserable job in predicting the change that has occurred in global temperature over the past two decades. You can see that for yourself by looking at the graph shown above. The various lines that have no circles or squares on them are the results of the climate models used by the IPCC. Notice that no model comes close to lining up with the actual data (the squares and circles). Indeed, the later the date, the worse the models become when compared to the data.
A group of retired NASA scientists and engineers led by Dr. Harold H. Doiron, a mechanical engineer who is best known for his work on eliminating unstable vibrations in liquid propellant rockets, has decided that these models simply can’t be used to make rational decisions about earth’s future climate. As this group says:
We have concluded that the IPCC climate models are seriously flawed because they don’t agree very closely with measured empirical data. After a 35 year simulation the models over-predicted actual measured temperatures by factors of 200% to 750%. One could hardly expect them to predict with better accuracy 300 years into the future required for use in regulatory decisions.
So what are we to do? If we can’t properly model how the earth will respond to increased carbon dioxide concentrations, how can we estimate what the consequences will be if we do nothing to curb the activities that are filling earth’s atmosphere with excess carbon dioxide?
In this research team’s mind, the answer is to look at the actual data and develop an empirical estimate. After all, we have about 100 years of measured data when it comes to global temperature, and we have a few thousand years of data that can help us estimate how the earth’s temperature has changed over that timeframe. In addition, we have measurements and estimates for how the amount of carbon dioxide in earth’s atmosphere has changed over time. If we look at past correlations between carbon dioxide and temperature, perhaps they can tell us what future correlations will be.
I have to admit that I am surprised no one has used this approach before. Sure, climate scientists have studied the correlations between past global temperatures and past atmospheric carbon dioxide concentrations, but this is the first time of which I am aware that scientists (and engineers) have tried to use those correlations to make definitive predictions about the future.
To those who spend a lot of time analyzing the global warming issue, the most important unknown is the climate sensitivity, which is defined to be the amount that global temperatures will increase when the amount of greenhouse gases in the atmosphere doubles. The IPCC currently estimates the climate sensitivity at somewhere between 2 and 4.5 degrees Celsius, with a most likely value of 3 degrees Celsius.
According to these retired NASA scientists and engineers, however, this is based on flawed computer models that have no connection to reality. In their report, they note that many peer-reviewed climate papers conclude that the climate sensitivity is much lower than the IPCC’s estimate. Indeed, in Figure 4.9 of their report, they show that 15 climate studies published in the peer-reviewed literature from 2011 to 2013 all conclude that climate sensitivity is much lower than the IPCC’s estimate.
What do the retired NASA scientists and engineers conclude in their report? They say that at maximum, the climate sensitivity for all greenhouse gases combined is 2.9. This means that if the total amount of greenhouse gases in the atmosphere doubled, the earth’s temperature would increase by 2.9 degrees Celsius. However, they conclude that if you just look at carbon dioxide, the climate sensitivity is only 1.8. Thus, if the amount of carbon dioxide in the atmosphere doubles (which is supposed to happen in 2080, according to current emission projections), the global temperature will rise only 1.8 degrees Celsius. This is far below what the IPCC concludes, but it is in line with the most recent peer-reviewed research on the issue.
In the end, here is what they conclude:
There is no convincing evidence that Anthropogenic Global Warming (AGW) will produce catastrophic climate changes. AGW can only produce modest amounts of global warming that will likely be beneficial when the substantial benefits to crop production from more CO2 in the atmosphere are considered.
As far as I know, none of the researchers involved in the project are climate scientists. Indeed, they call themselves “The Right Climate Stuff Research Team” to emphasize that they are among the scientists and engineers who put men on the moon. While that is very impressive, it has little to do with climate science. At the same time, however, their analysis is rather unique, and I like their approach. Given that we know the climate models used by the IPCC are downright awful, using past data to make predictions about future climate might very well be a much better way to go.