A major new international report shows last year again broke climate records, with the highest ever recorded greenhouse gases, ocean heat and global sea level rises.
Carbon dioxide, methane, and nitrous oxide, which are the three largest contributors to the Earth's warming, all hit highs.
CO2 concentrations in the atmosphere were the highest detected in 800,000 years, and grew at the fifth-highest rate since 1958, the start of the instrumental record.
The increase since the end of the last ice age has been so fast that on this time scale, it looks practically instantaneous.
La Niña contributed to the warmest year on record for New Zealand.
Read highlights of the report here, and the full report here.
A graph shows the fluctuations in C02 concentrations in the atmosphere over the past 800,000 years. Photo / NOAA Climate.gov
Other key findings for 2021
• Global drought continued in 2021 and peaked at 32 per cent of global land areas in August.
• Rains failed for third season in east Africa, worst threat to food security there for 35 years.
• Canada broke national heat record by 4 degrees, with 49.6C, European heatwave likely broke temperature record.
• Arctic sea ice had its ninth smallest winter expansion, and its 12th smallest minimum.
• Above average or near record northern hemisphere hurricane season, global average was down.
More than 530 scientists in 60 counties contributed to the publication of the State of the Climate in 2021 report, the 32nd year it has been released.
It comes as massive flooding has killed more than 1000 people in Pakistan, leaving millions homeless and vast swathes of the country underwater.
On Tuesday, a new study showed a quarter of a metre of sea level rise was now inevitable from Greenland's ice melt alone - even if all climate-damaging actions stopped immediately.
Large areas of Auckland and Wellington's foreshore would be at risk from as little as 10cm of sea level rise.
A separate OECD study released on August 29 showed member countries had a huge increase in fossil fuel subsides last year as energy prices rose.
In July, the New Zealand Government announced it was extending its reduction of petrol excise duties and road user charges until the end of January 2023 in response to the ongoing volatility of fuel prices and the cost of living crisis.
One of the few truly effective ways of drastically reducing emissions is to stop burning fossil fuels.
A graph shows the difference from average global surface temperature from six different sources. Photo / NOAA Climate.gov
'Climate change has global impacts and shows no sign of slowing'
"The data presented in this report are clear - we continue to see more compelling scientific evidence that climate change has global impacts and shows no sign of slowing," report author Rick Spinrad said.
"With many communities hit with 1000-year floods, exceptional drought and historic heat this year, it shows that the climate crisis is not a future threat but something we must address today."
Global ocean heat continued to increase and reached new record highs in 2021.
For the 10th consecutive year, global average sea level rose to a new record high and was about 97mm higher than the 1993 average - the year that marks the beginning of the satellite measurement record.
The rise in land and sea temperatures was despite the continuing La Niña weather pattern, which lowers temperatures in the northern hemisphere.
La Niña contributed to the warmest year on record for New Zealand, but also to the coolest year since 2012 for Australia.
Huge swings in Antarctica temperatures alarming - NZ scientist and study editor
Te Herenga Waka-Victoria University of Wellington climate science lecturer Dr Kyle Clem and lead editor of the report's chapter on Antarctica and the Southern Ocean said 2021 was another year of extremes in the region.
Huge and rapid swings in sea ice coverage were observed, with new record-low daily coverage in October and December after it had been above average for autumn and winter.
Clem said there had been a massive loss of ice since 2003, adding to sea level rise.
But the loss last year was lower than the long-term trend because of gains from heavy snow fall on other parts of Antarctica, which was linked to an unusual number of extreme weather events, he said.
Parts of the continent had extreme cold, and others record high temperatures, but the winter did not significantly affect the long-term warming trend at the South Pole and the region continues to warm more than twice as fast as the global average.
Last year also saw the second longest-lived ozone hole on record, but there were signs that was "healing" compared to the early 2000s.
