An accountant compared the raw data first from several stations in Paraguay, then elsewhere in South America. All the data was "adjusted" to show global warming, or at least more global warming than has actually occurred.
[Paul] Homewood checked the data on three weather stations in Paraguay and found that all three had their initial raw readings adjusted to show lower temperatures in the 1950s and higher temperatures today.And it is not just in South America.
Traust Jonsson, a longtime climate researcher in Iceland was surprised to see the revised data "disappears" Iceland’s "sea ice years" around 1970, when a period of extreme cooling almost wiped out Iceland's economy.Article: Massive Tampering With Temperatures In South America
This is the original article. It has flashing .gifs that show how the data was manipulated.
This report is consistent with reports from elsewhere, including Australia.