By Philip J. Lloyd
Original link: http://multi-science.atypon.com/doi/abs/10.1260/0958-305X.26.3.417
Unfortunately, you have to pay $35 to get the entire article, but the abstract alone gives important data. Basically, according to ice core temperature (Antarctic? Greenland? Both?) readings, changes of temperature up to a degree C per century are normal. The 0.8 degree C temperature increase in the 20'th century may then be largely duty to natural variation, although rising CO2 levels must be a contributor too. But beware: it's not clear from the abstract whether these temperature trends truly are global or just local; that must be in the actual report (assuming a minimum of peer review), so if you're willing the $35, please let me know
Abstract
There has been widespread investigation of the drivers of changes in global temperatures. However, there has been remarkably little consideration of the magnitude of the changes to be expected over a period of a few decades or even a century. To address this question, the Holocene records up to 8000 years before present, from several ice cores were examined. The differences in temperatures between all records which are approximately a century apart were determined, after any trends in the data had been removed. The differences were close to normally distributed. The average standard deviation of temperature was 0.98 ± 0.27 °C. This suggests that while some portion of the temperature change observed in the 20th century was probably caused by greenhouse gases, there is a strong likelihood that the major portion was due to natural variations.
