Climate crisis: 'The alarm bells are deafening, and the evidence is irrefutable'

Heatwaves and other extreme weather events have become more intense and frequent since the 1950s, while human behaviour is "virtually certain" to be the cause of melting glaciers and the decrease in Arctic ice since the 1990s, the report said.

Carbon dioxide concentration is the highest it has been in at least 2m years, sea levels are rising at the fastest rate in 3,000 years, Arctic sea ice levels are at their lowest in at least 1,000 years, and glaciers are in retreat in unprecedented levels over the past 2,000 years.

On the course the planet is on, there is a possibility of a rise in sea levels of about 2m by the end of this century, and even a 5m rise by 2150, which would place hundreds of millions of people in peril in coastal communities.

The alarm bells are deafening, and the evidence is irrefutable. Greenhouse gas emissions from fossil fuel burning and deforestation are choking our planet and putting billions of people at immediate risk. 

"Global heating is affecting every region on earth, with many of the changes becoming irreversible,” Mr Guterres said.

The internationally agreed threshold of 1.5C, the limit that countries have pledged to try to keep to avoid some of the worst consequences of the climate crisis, is already perilously close, Mr Guterres said. 

“We are at imminent risk of hitting 1.5C in the near term. The only way to prevent exceeding this threshold is by urgently stepping up our efforts, and pursuing the most ambitious path. We must act decisively now to keep 1.5C,” he added.

The 234 scientists who analysed 14,000 research papers believe 1.5C will be reached by 2040 in all scenarios, but warn that if carbon emissions are not drastically reduced in the coming years, that temperature increase will happen even sooner.

The head of the United Nations Environment Programme, Inger Andersen, said the world and political leaders have heard the warnings but not reacted.

"You have been telling us for over three decades of the dangers of allowing the planet to warm. The world listened, but did not hear. The world listened, but it did not act strongly enough and, as a result, climate change is a problem that is here now. It’s time to get serious because every tonne of CO2 emission adds to global warming," she told the scientists as they unveiled their findings.

Prof Peter Thorne of Maynooth University, who is coordinating lead author of the IPCC report, told RTÉ's Brainstorm that today's climate has not been seen in at least many thousands of years. 

"It is probably in a state unseen since 125,000 years ago, the peak of the last interglacial when alligators roamed Trafalgar Square in London," he said.

The IPCC will now turn its focus to next year, when it will release two new reports. The first will examine the impacts of the climate crisis globally, while the second will examine potential solutions to avoid catastrophic consequences.

The IPCC is the UN body for assessing the science related to climate change. It was established by the United Nations Environment Programme (UNEP) and the World Meteorological Organization (WMO) in 1988 to provide political leaders with periodic scientific assessments concerning climate change, its implications and risks, as well as to put forward adaptation and mitigation strategies.

There are 195 countries signed up to the body.