"Natural climate variability hinders the detection of any man-made warming trend. While the state of the climate clearly involves much more than just global temperature, changes in global temperatures do indicate the scale of different climatic events, both natural and man-made.

The range of natural year-to-year temperature variations is quite similar to the size of the warming that appears to have occurred over the past century (0.3-0.6 °C). Moreover, the 16th to 18th centuries appear to have been unusually cold, and the climate may still be recovering from that time. So scientists cannot yet claim to have found an unambiguous temperature-related greenhouse signal."