Adding weight to arguments that global warming is upon us, a study appearing today in the journal Science concludes that 26 bodies of water in the Northern Hemisphere are freezing an average of 8.7 days later and thawing out 9.8 days earlier than they did 150 years ago. The study was a based on direct human observations and records, not on extrapolations or calculations. David R. Easterling, chief scientist at the National Climatic Data Center in the U.S., said the study “provides independent evidence that the warming we have seen over the 20th century is real.” But the study authors noted that although some of the warming they found may be attributable to human causes, some of it “may be related to other drivers, such as changes in solar activity.” Meanwhile, a draft report from the U.N. Intergovernmental Panel on Climate Change says the air temperature of the planet may rise between 1 and 5 degrees Celsius by 2100, an increase from its previous estimate of between 1 and 3.5 degrees, says the IPCC’s Robert Watson.