Emissions of greenhouse gases combined with the El Nino phenomenon has made 1998 the warmest year on average over Earth since the end of 19ème century, followed in descending order by 2002, 2003 and 2004, scientists said Thursday Nasa.
"We observed a clear warming trend these 30 recent years mainly due to the increase in atmospheric greenhouse gas emissions," said James Hansen, climatologist at the Goddard Institute for Nasa space studies.
In 2004 the average global temperature of the Earth was $ 14 degrees Celsius (57 degrees Fahrenheit) or 0,48 ° C (0,86 ° F) more on average than during the period in 1951 1980, says Hansen, quoted on the website of NASA.
The regions of the globe have experienced the greatest increase in temperature were Alaska, the Caspian region and the Antarctic sea.
The solar energy trapped in the atmosphere by the accumulation of gas greenhouse-especially carbon monoxide from industries and automobiles- combined aware Pacific El Nino could make 2005 an even warmer year than 1998, said NASA.
The agency is now warming as it affects the seasons hottest making them permanently.
To determine if the Earth warms or cools, scientists fall temperatures in many parts of the world on the ground (by meteorological stations) and the ocean surface (satellite).
They then calculate the median temperature so as to establish an average temperature over the entire surface of the Earth.