The world’s temperature is expected to rise by at least 1.5 degrees Celsius in the next 20 years, a United Nations-backed report has found.
The increase is the temperature warming limit agreed to, compared to pre-industrial levels, by nearly 200 countries nearly five years ago in the Paris Agreement, with nations committing to substantially reduce greenhouse gas emissions.
The new estimate is a finding from an Intergovernmental Panel on Climate Change (IPCC) report assessing the latest available climate science research.
“This report is a reality check,” IPCC Working Group I co-chair Valérie Masson-Delmotte said in a press release.
“We now have a much clearer picture of the past, present and future climate, which is essential for understanding where we are headed, what can be done, and how we can prepare.”
The report states that without large-scale and immediate reductions of carbon dioxide and other greenhouse gas emissions, limiting warming to near 1.5 degrees Celsius or even 2 degrees Celsius will be impossible.
"That's a sort of taste of the future, we'll see more of those events and bigger and eventually some communities are going to be overwhlemd in places as they have been in other countries," IPCC coordinating lead author Professor James Renwick said.
"If we allow the warming to get much beyond 1.5 degrees and we're already at 1.1, you know there's going to be more damage, more cost, more lives lost so I find it pretty frightening, actually."
Changes to the world’s climate, especially in areas like the ocean and ice sheets, caused by past and future greenhouse gas emissions will be irreversible for thousands of years.
Climate Change Minister and Green Party co-leader James Shaw says the report "really underscores the urgency and the importance of having a really strong emission reductions plan in response to the Climate Commission's advice".
As global warming increases, Earth is seeing increases in the intensity and frequency of extreme hot weather events, heavy rain, marine heatwaves and drought, as well as reductions in the amount of Arctic sea ice, frozen ground (permafrost) and snow.
Every region has been affected with many of the observed changes reported as unprecedented in at least thousands of years.
Human activities have caused approximately 1.1 degree Celsius of warming through emissions from 1850 to 1900.
The report, Climate Change 2021 The Physical Science Basis, was written by 234 climate authors from 66 countries, including New Zealand.