Climate change sceptics such as Nigel Lawson who argue that global warming has stopped have their "heads in the sand", according to the Met Office.

A recent dip in global temperatures is down to natural changes in weather systems, a new analysis shows, and does not alter the long-term warming trend.

The office says average temperatures have continued to rise in the last decade, and that humans are to blame.

In a statement published on its website, it says: "Anyone who thinks global warming has stopped has their head in the sand. The evidence is clear, the long-term trend in global temperatures is rising, and humans are largely responsible for this rise. Global warming does not mean that each year will be warmer than the last."

The new research confirms that the world has cooled slightly since 2005, but says this is down to a weather phenomena called La Niña, when cold water rises to the surface of the Pacific Ocean. Despite this effect, the office says, 11 of the last 13 years were the warmest ever recorded.

Vicky Pope, of the Met Office, said the research was a response to claims made by Lawson, a former chancellor, and others that the recent cooling showed fears of climate change were overblown, and temperatures were unlikely to rise as high as predicted. She said: "It has confused people. We got a lot of emails asking whether global warming had stopped and it prompted us to look at the data again."

The apparent cooling trend was exaggerated by a record high in 1998 caused by a separate weather event, El Niño, she said. "You could look at what happened in 1998 and say that global warming accelerated, and that's not true either."