Led by a strong El Nino, 2015 may turn out to be the hottest year, according to the World Meteorological Organization (WMO).

The weather agency has cited global warming as another reason for a rise in global temperature.

This year's El Nino, a phenomenon often linked to poor monsoon rainfall in India, has already resulted in "extreme weather patterns" across the world and the WMO forecasts it to get even stronger by the end of 2015.

"The full effect of the strong 2015 El Nino on global temperature is likely to continue after El Nino peaks. However, other impacts are already being felt," said the WMO.

The global average surface temperature in 2015 could reach the symbolic and significant milestone of 1° Celsius above the pre-industrial era, it said.

A preliminary estimate reached from measuring the data from January to October revealed that the global average surface temperature for 2015 so far was around 0.73 °C above the 1961-1990 average of 14.0°C and roughly 1°C above the pre-industrial 1880-1899 period.

"The state of the global climate in 2015 will make history as for a number of reasons," said WMO Secretary-General Michel Jarraud.

"Levels of greenhouse gases in the atmosphere reached new highs and in the Northern hemisphere spring 2015 the three-month global average concentration of CO2 crossed the 400 parts per million barrier for the first time. 2015 is likely to be the hottest year on record, with ocean surface temperatures at the highest level since measurements began," said Jarraud.

The 2011-2015 period has been the warmest five-year period on record, witnessing extreme weather events -particularly heatwaves-influenced by climate change, said WMO

"This is all bad news for the planet," he added.

The US National Oceanic and Atmospheric Administration (NOAA) said that this year's October was recorded as the hottest October in the past 136 years.