World Meteorological Organization predicts 2017 will be third hottest year

Extreme flooding events - like April's flood in Edgecumbe after the Rangitaiki River stopbank broke - are likely to be directly linked to global warming, scientists say. Photo / Whakatane Beacon

2017 is set to be in the top three hottest years on record, according to the World Meteorological Organization - and Kiwi scientists say the impact of the changing climate is hitting home in New Zealand already.

Only 2015 and 2016 may be hotter than this year, with temperatures in both years boosted by an very strong El Niño weather pattern.

Long-term signs of climate change, including growing carbon dioxide concentrations, sea level rise and ocean acidification, also show no signs of slowing down, the WMO said.

Arctic sea ice coverage is still below average and Antarctic sea ice extent is at or near a record low.

The WMO released its provisional statement on the state of the climate to coincide with the start of the United Nations climate change conference in Bonn, where countries meet to discuss how to slow human-cause global warming.

The meeting's urgency has become apparent as the organisation's latest climate report, released on Sunday, shows the Paris Accord's goal of staying below 2C of global warming is looking unlikely.

Climate change is mainly felt through extreme events, Victoria University climate scientist Professor James Renwick said.

Such events have characterised 2017 - from record floods and fires in North America to record monsoon rains in Bangladesh and India and record-breaking heatwaves.

A winter storm brought a record day of flooding in Oamaru in July. Photo / Waitaki Aquatic Centre

But New Zealand has also seen major flood events this year, including the devastating flood of Edgecumbe in April and the eastern South Island in July, Renwick said.

"While the analysis has yet to be done, it is very likely that these events have a climate change 'fingerprint', as a warmer atmosphere can hold more moisture, making heavy rain events more frequent.

"Sea levels continue to rise, and the latest science shows that we may see considerably more than 1m this century, with many more metres to come, unless we cap greenhouse gas emissions urgently."

The meeting in Bonn was time for countries to act on climate change, he said.

"To stay below the two-degree Paris limit, the world economy needs to be carbon-free within 50 years. A huge ask, but the costs of inaction or failure are almost incalculable."

University of Otago honorary research fellow Dr Jim Salinger pointed to the July storms which brought Oamaru's wettest day on record (174mm), the second wettest day in Winchmore (151mm) and Dunedin's wettest July day on record (94 mm).

Floods and inundation because of sea level rise will increase in future, Salinger said.

Otago Regional Council figures showed there were almost 3000 homes in South Dunedin that are half a metre above sea level, making the suburb the most at-risk in New Zealand.

Ice volume calculations also show the volume of snow and ice on the Southern Alps is shrinking, and is now 60 per cent lower than in 1977, Salinger said.

Australians have also been warned they face dire consequences as temperatures rise.

Dr Liz Hanna, an Honorary Senior Fellow at the Climate Change Institute at the Australian National University, said warming "should be sending alarm bells" to those living in Australia, where temperatures are over 10C hotter than the global average.

Extra warming will bring more frequent, longer and more intense heat waves, he said.

"Temperatures over 50C are coming, and we simply cannot keep functioning in such temperatures where we cannot move and cannot work without overheating.

"Air-conditioning can only ever provide limited relief, and only to some. Trees, animals and people all wilt in the heat."