Government scientists are deliberately changing climate data, which shows a warming trend in the United States as opposed to a cooling trend, according to a report. The Daily Caller reports the practice of altering temperature data is not new — nor is it a secret. Scientists say it is for correcting errors in data, particularly in the early years of record keeping.Critics say the practice is an effort to show global warming is a real, man-made phenomenon that is getting worse year by year."[The National Climatic Data Center] pulls every trick in the book to turn the U.S. cooling trend into warming. The raw data shows cooling since the 1920s," a science blogger who goes by the name Steven Goddard told The Daily Caller."NCDC does a hockey stick of adjustments to reverse the trend. This includes cooling the past for 'time of observation bias' in filling missing rural data with urban temperatures, and doing almost nothing to compensate for urban heat island effects."Another expert in the field, climate scientist Dr. Roy Spencer, said he noticed a significant difference in climate data when he was updating some figures using the NCDC's website. The data he looked at this month was different than what he looked at last March — data taken from the same time period."I was updating a U.S. Corn Belt summer temperature and precipitation dataset from the NCDC website, and all of a sudden the no-warming-trend-since-1900 turned into a significant warming trend," Spencer wrote on his blog Monday.Spencer calculated the warming trend for that region of the U.S. increased from 0.2 degrees per century to 0.6 degrees per century after the data was changed, the Caller reported."A variety of errors in data measurement and collection would typically have both positive and negative signs," Spencer wrote. "In contrast, the thermometer data apparently need to be adjusted in such a way that almost always leads to greater and greater warming trends."The National Oceanic and Atmospheric Administration claims it tweaks temperature figures to account for factors like the time of day the temperature was recorded and concerns with land versus ocean data.By shifting the official temperature reading from any given day to the morning instead of the afternoon, a warming trend was created, reports The Daily Caller.This is not the first time government scientists have been accused of manipulating weather data to show a warming trend. Last month, a report claimed data from weather stations in South America has been adjusted since the 1950s to help support the theory of global warming. Global warming has a deep history, dating back to scientists in the 1700s who planted the seeds of the issue that has become almost as political as it is scientific.