It warmed up, cooled down, warmed up and warmed up again
The year 2004 ranks fourth in the list of the hottest years since systematic temperature measurements began around the world in the 19th century, NASA scientists said Tuesday. Extremely high temperatures were measured in Alaska, the Caspian Sea region and Antarctica. In contrast, the USA was unusually cool. According to Dr. James Hansen, director of the Goddard Institute for Space Research at NASA, the average temperature in the world this year coincides with the trend of rising temperatures, which has been going on for 30 years "and is mainly due to the growing greenhouse effect".
The highest temperatures were measured in 1998, when temperatures rose due to a severe El Nino phenomenon in the Pacific Ocean. The years 2002 and 2003 were ranked second and third.
The fact that the warming in recent years is an unusual phenomenon was substantiated by another study, which surveyed the temperatures in the Northern Hemisphere in the last 2,000 years based on indirect evidence such as tree trunk rings, sentinels in stalactite caves and sea floor layers.
The study, published in the journal "Nature", revealed that in the previous heat records, mainly around the year 1000, the temperatures were similar to the average in the twentieth century. Only the temperatures of the last 15 years have no parallels in the previous millennium.
The new study is one of a series of studies that challenge the theory that temperatures in the Northern Hemisphere almost did not change until the beginning of the 20th century, and only in the last century has there been a noticeable warming - a graph that has earned the nickname "hockey stick". According to the new study, there were significant fluctuations in temperatures between the 12th and 20th centuries, with around 1600 being a particularly cold period.
The lead author of the new study, Anders Moberg of Stockholm University, said it is important to recognize that natural processes affecting the climate may reduce or add to human-caused warming in future years. However, Norberg added that his research "must not be used as ammunition for those who doubt the greenhouse effect".
