Climate change: IPCC report warns of ‘irreversible’ impacts of global warming

By Matt McGrath
Environment correspondent

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Many of the impacts of global warming are now simply "irreversible" according to the UN's latest assessment.

But the authors of a new report say that there is still a brief window of time to avoid the very worst.

The Intergovernmental Panel on Climate Change says that humans and nature are being pushed beyond their abilities to adapt.

Over 40% of the world's population are "highly vulnerable" to climate, the sombre study finds.

But there's hope that if the rise in temperatures is kept below 1.5C, it would reduce projected losses.

Just four months on from COP26, where world leaders committed themselves to rapid action on climate change, this new UN study shows the scale of their task.

"Our report clearly indicates that places where people live and work may cease to exist, that ecosystems and species that we've all grown up with and that are central to our cultures and inform our languages may disappear," said Prof Debra Roberts, co-chair of the IPCC.

"So this is really a key moment. Our report points out very clearly, this is the decade of action, if we are going to turn things around."

This report from the IPCC is the second of three reviews from the world's foremost body of climate researchers.

Last August, the first instalment highlighted the scale of the effect that humans were having on the climate system.

This new report looks at the causes, impacts and solutions to climate change. It gives the clearest indication to date of how a warmer world is affecting all the living things on Earth.

Image source, Saddam Mohamed
Image caption,
A prolonged drought in Somalia has had major impacts on families, causing displacement

The report is a stark account of the fierce consequences that the world is already experiencing, like growing numbers of people dying from heat.

But the authors say that there is still a brief window of time to avoid the very worst.

"One of the things that I think is really, really clear in the report is that yes, things are bad, but actually, the future depends on us, not the climate," said Dr Helen Adams, a lead author on the report from King's College, London.

The report shows that extreme weather events linked to climate change like floods and heatwaves are hitting humans and other species much harder than previous assessments indicated.

The new study says that these impacts are already going beyond the ability of many people to cope.

While everyone is affected, some are being hit much harder. This outcome very much depends on where you live.

Between 2010 and 2020, 15 times more people died from floods, droughts and storms in very vulnerable regions including parts of Africa, South Asia and Central and South America, than in other parts of the world.

Nature is already seeing dramatic impacts at the current level of warming.

Coral reefs are being bleached and dying from rising temperatures, while many trees are succumbing to drought.

Image source, NurPhoto

The report highlights the increasing impacts that are expected as the rise in global temperatures, currently around 1.1C, heads to 1.5C.

Continued and accelerating sea level rise will increasingly hit coastal settlements pushing them towards "submergence and loss".

Under all emissions scenarios, the IPCC expects a billion more people to be at risk from coastal specific climate hazards in the next few decades.

If temperatures rise to between 1.7 and 1.8C above the 1850s level, then the report states that half the human population could be exposed to periods of life-threatening climatic conditions arising from heat and humidity.

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"I've seen many scientific reports in my time, but nothing like this," - UN Secretary General Antonio Guterres

Commenting on the summary, UN Secretary General Antonio Guterres described it as an "atlas of human suffering". He has no doubt as to where the blame lies.

"The facts are undeniable. This abdication of leadership is criminal. The world's biggest polluters are guilty of arson of our only home."

Health a growing concern

Diseases will likely spread more quickly in the coming decades, say the study's authors.

There is a particular risk that changing climactic conditions will ease the spread of mosquito-borne dengue fever to billions more by the end of this century.

As well as the physical health impacts, this report, for the first time, states that climate change may be exacerbating mental health issues, including stress and trauma related to extreme weather events and the loss of livelihoods and culture.

Warming threats to species

  • About half of the living organisms assessed in the report are already moving, to higher ground or towards the poles.
  • While up to 14% of species assessed will likely face a very high risk of extinction if the world warms by 1.5C, this will rise to up to 29% of species at 3C of warming.
  • For creatures living in areas that are classed as vulnerable biodiversity hotspots, their already very high extinction risk is expected to double as warming rises towards 2C, and to go up tenfold if the world goes to 3C.

Some researchers have speculated that going over 1.5C for a short period would be acceptable if temperatures came back down below the level soon afterwards.

This report says there are dangers with this approach.

"In any overshoot there's an increasing risk of hitting tipping points and triggering feedback, in the climate system, like permafrost thawing," said Linda Schneider from the Heinrich Boll Institute, who was an observer at the IPCC discussions.

"That would make it a lot more difficult, it could make it impossible to get back below 1.5C."

Image source, RIJASOLO
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Flooding in Madagascar left devastation in its wake

The report is disdainful of technological fixes like deflecting the Sun's rays or removing carbon dioxide from the air, saying they could make things worse.

The summary for policymakers puts much focus on "climate resilient development," which it says helps build the strength to cope with climate change in every society.

"If our development pathways are ones in which health systems don't improve much, education doesn't improve much, our economies aren't growing very fast and inequality remains a big problem, that's a world where a particular amount of climate change is going to have a really big impact," said Prof Brian O'Neill, an IPCC coordinating lead author from the Pacific Northwest National Laboratory in the US.

"In contrast, if it's a world where we are really making rapid progress on education and health and poverty, if climate change is imposed on that society, the risk will be much lower."

Follow Matt on Twitter @mattmcgrathbbc.