The president of the World Bank, Jim Yong Kim, told BBC News that warming could no longer be ignored.
He urged action to reduce emissions to minimise the likelihood of disasters like Typhoon Haiyan, which has claimed thousands of lives in the Philippines.
The Intergovernmental Panel on Climate Change (IPCC) said that the jury is out on whether the frequency of tropical cyclones will increase, but WMO's head Michel Jarraud said it was expected that the impact of storms would be more intense.
All of the warmest years have been since 1998, and this year once again continues the underlying, long-term trend. The coldest years now are warmer than the hottest years before 1998, he said.
He added that atmospheric concentrations of carbon dioxide and other greenhouse gases reached new highs in 2012, and we expect them to reach unprecedented levels yet again in 2013. This means that we are committed to a warmer future.