Jeff Masters in his blog at Weather Wunderground recommended Michael Mann's new book "The Hockey Stick and the Climate Wars," so I bought the Kindle version and am reading it. The book tells of the science Mann and his collaborators did to develop the concept of the graph of earth's temperature over the past year to produce the Hockey Stick graph. That graph implies that there is a temperature anomaly for the past few decades and the earth's temperature is rising at a very rapid rate. He and a significant majority of the paleoclimatologists believe that this increase is the result of human activity, namely CO2, and without stopping the emission of CO2 and other greenhouse gases, the earth's climate could become unsuitable for human habitation.
The book also tells of the attempts by certain interests to discredit the science and the scientists and to deny that there is any problem and especially that humankind could be the cause.
I read some of the early climatology reports coming out in 1998 and 1999, and even more around 2006 when I started on my book "Was a Time When." In my mind, by that time the arguments that the earth's temperature was climbing were solid, and the correlation between that rise and human activity was very high. I projected the trends ahead and concluded that over the next 100 years the weather would go to hell, droughts would cause worldwide famine, and the sea levels would rise even faster than the conservative estimates of the day. When those effects were mixed with resource depletion and population overshoot, the result would be the Great Collapse of our civilization.
So I am on the side of Michael Mann.
The book is a tough read. It helps to have some past experience in statistics to understand the methods being used to extract trends out of the data and proxy data on the temperature of the earth. I have enough to get the jist, but not enough to fully understand the method.
Mann is very direct in his discussions about the efforts of several groups to discredit him and other climatologists. It is discouraging, because I see a lot of that same intent still existing in The Powers That Be.
I am about 40% through the book, so there is more to learn, but the trend in the book is constant. It is almost enough to make an old fart like me give up. I will add more comments when I am done.