Here's an interesting bit about some of the evidence used to make the case for global warming. We'll quote exerpts from a post by the author of "Climate of Extremes: Global Warming Science They Don't Want You to Know" on the National Review site:
"......the weather data that go into the historical climate records that are required to verify models of global warming aren't the original records at all. Jones and Wigley, however, weren't specific about what was done to which station in order to produce their record, which, according to the IPCC, showed a warming of 0.6° +/- 0.2°C in the 20th century.
Now begins the fun. Warwick Hughes, an Australian scientist, wondered where that "+/-" came from, so he politely wrote Phil Jones in early 2005, asking for the original data. Jones's response to a fellow scientist attempting to replicate his work was, "We have 25 years or so invested in the work. Why should I make the data available to you, when your aim is to try and find something wrong with it?..............
.............Roger Pielke Jr., an esteemed professor of environmental studies at the University of Colorado, then requested the raw data from Jones. Jones responded:
Since the 1980s, we have merged the data we have received into existing series or begun new ones, so it is impossible to say if all stations within a particular country or if all of an individual record should be freely available. Data storage availability in the 1980s meant that we were not able to keep the multiple sources for some sites, only the station series after adjustment for homogeneity issues. We, therefore, do not hold the original raw data but only the value-added (i.e., quality controlled and homogenized) data.
The statement about 'data storage' is balderdash. They got the records from somewhere. The files went onto a computer. All of the original data could easily fit on the 9-inch tape drives common in the mid-1980s. I had all of the world's surface barometric pressure data on one such tape in 1979."
So, did the evidence really ever exist? You can read the whole item here: