The Unsettled Science of Climate Change

Climategate seems to actually be a good thing for climate change. It is getting more people involve in learning what is truly relevant in the unsettle science. Professor Gavin Schmitt recently used the term unsettle science as the title of a blog post on realclimate.org. Gavin mentions a few of the unsettle details but missed one that should be note worthy.

Gavin has stated in the past that the greenhouse gases are the cause of warming since the 1950's because temperatures should have cooled due to Total Solar Irradiance (TSI) and volcanic activity. I will give him the volcanic activity part, but the TSI part is a little more up in the air.

The reason it is up in the air is because he stated that warming from circa 1900 to 1950 was "due to the sun". That conclusion is partially based on an outdated paper by Dr. Judith Lean et al in 2000. Since that paper was published there have been a variety of papers by other authors that greatly down play the role of TSI or solar variability on climate. Humorously, that same paper is also used by skeptics to prove that warming is due to the sun not greenhouse gases. Without regard to how the paper is interpreted, it is still outdated and results from that time frame do not include more recent and more accurate satellite data. Dr. Leif Svalgard has a nifty Excel graphic showing a variety of solar reconstructions and the Lean reconstruction shows nearly twice as much solar influence as the other more current reconstructions. If more current TSI information is used the water begins to get muddy on how accurate Gavin statement is.

This is not the only example of how the roles of solar and other natural climate variables are not perfectly understood. Professor A. A. Tsonis of the University of Wisconsin, Milwaukee published an interesting paper on a New Dynamical Mechanism for Major Climate Shifts. The following is a quote from the conclusions of Tsonis et al 2007:

"It is interesting to speculate on the climate shift after the 1970s event. The standard explanation for the post 1970s warming is that the radiative effect of greenhouse gases overcame shortwave reflection effects due to aerosols [Mann and Emanuel, 2006]. However, comparison of the 2035 event in the 21st century simulation and the 1910s event in the observations with this event, suggests an alternative hypothesis, namely that the climate shifted after the 1970s event to a different state of a warmer climate, which may be superimposed on an anthropogenic warming trend."

So how much is due to which, greenhouse gases or natural variability is pretty much in question. There are a variety of other papers that could be referenced that question the amount of warming due to purely greenhouse gas increases.

Do not imply from this that there is no warming due to the greenhouse effect. The how much is only in question because the response of the atmosphere to warming is not well understood. The warming due to carbon dioxide alone could cause over one degree of warming which is one third roughly of the predicted warming. Professor Richard Lindzen of MIT has an interesting paper, Taking Greenhouse Warming Seriously, for those that want to know more about the unsettled science.

Neither should you imply that reasonable precautions should not be taken to reduce greenhouse gas emissions. What is reasonable is a financial and political decision that should be based all the current science not just the science from the Cimategate tribe. Hopefully, the Copenhagen Climate Summit will have access to all the science.