Each month so far has broken previous global temperature records and scientists believe this year may even be the warmest of the millennium.
Thousands of readings from satellites and weather stations across the globe have confirmed that the world has been warmer this year than at any time since 1880, when Britain's Met Office collected the first reliable measurements of global temperatures.
Scientists who have estimated temperatures from past centuries by the growth of tree rings said this spring may have been the hottest in a thousand years, despite the cold start to the British summer.
The US's National Oceanic and Atmospheric Administration (NOAA), which gathered the global temperature data, said every month from January to May "far exceeded" previous records.
In Britain, every month except April has been significantly warmer than the 30-year national average for that month. January and February were 1.5 degrees C and 3.4 degrees above average.
So far, the world is 0.25 degrees warmer than in 1997, which is the warmest year on record. Scientists said the increase, though small, is enough to suggest global warming, rather than errors.
Scientists at the NOAA said El Nino, a disturbance in the Pacific Ocean currents which affect weather patterns across the globe, is largely responsible for the record temperatures. They said global warming might be exacerbating the phenomenon.
"El Ninos are occurring more frequently and are progressively warmer. There is evidence to suggest global temperatures may be linked to stronger, more frequent El Ninos," the NOAA said.
Sir John Houghton, co-chairman of the scientific committee of the International Panel on Climate Change, said the latest data on global temperatures supported the international scientific consensus that human activity might be making global warming worse. "These measurements are going in the direction we expect," he said. "If we really are seeing that each month of this year is the hottest ever, it is pretty unlikely to be a chance effect.
"We think the world is warming up because of the burning of fossil fuels and an increase in carbon dioxide in the atmosphere. But at present we cannot prove this because of variability in the climate."
Some scientists dispute whether man-made gases cause global warming but Houghton believes they are wrong. "Everyone agrees that we are beginning to see the signals through the fog. These latest measurements will add to the pile of evidence in support of global warming," he said.
t Scientists have shown for the first time how sunspots may be linked to changes in the weather in a breakthrough that could lead to a radical rethink in weather forecasting.
Until now, no one has been able to explain how solar activity might affect the weather, even though records suggest an influence exists. But Professor Terry Robinson and Dr Neil Arnold at Leicester University have constructed a computer model which shows how changes in electromagnetic radiation emitted by the Sun can cause significant atmospheric changes on Earth.Reuse content