Temperature records tumbled in Russia, Saudi Arabia, Sudan, Burma and Pakistan, causing heatwaves and devastated harvests.

2010 was the year of the heatwave, with record temperatures set in 17 countries. Two leading groups of scientists say it was the warmest since records began in 1850; another suggests it was the second-warmest.

But the year that saw an unprecedented month-long heatwave in Russia will be followed by cooler global temperatures in 2011, say climate scientists monitoring sea temperatures in the Pacific that are thought to determine temperatures around the world.

The final ranking of 2010 will not become clear until November and December data are available in early 2011, but November global temperatures are similar to those observed in November 2005, suggesting 2010 is on track for near-record levels.

This decade also proved to be the hottest on record, with temperatures averaging 0.46C above the 1961-90 average, 0.03C above the 2000-09 mean and the highest value yet recorded for a 10-year period.

The Russian heatwave, which saw temperatures in Moscow nearly 15C above normal for a month, led to thousands of deaths as well as forest fires across a wide region. But the heatwave extended across the Middle East, and northern India, devastating harvests and leading to food shortages.

Previous temperature records tumbled in 17 countries including Russia, Ukraine, Finland, Chad, Kuwait, Burma, Sudan, Niger and Saudi Arabia. Pakistan had Asia's hottest-ever recorded day when the temperature in the abandoned city of Mohenjo-daro in Sindh province reached 53.5C.

The most extreme temperature anomalies in 2010 occurred across most of Canada and Greenland, where annual temperatures were 3C or more above normal, and across much of Africa and south Asia, where annual temperatures were 1-3C above normal.

Guinea, in west Africa, was the only country in the world to have recorded a record low temperature in 2010, but says the World Meteorological Organisation, below-normal temperatures were recorded in Siberia, parts of South America, interior Australia and the south-east United States.

Britain, Germany, France and Norway all had their coolest years since 1996 due mainly to below-normal temperatures during the winter.

This was also the year that CO2 levels in the atmosphere bounced back after a slight fall caused the previous year's recession in 2009.

Data will not be complete for several weeks, but according to monitoring stations in Hawaii and Norway, levels were on course to grow slightly on record 2008 levels.