Evidence is growing that catastrophic climate change "tipping points" are nearing, from surging sea levels as polar ice melts to spiking temperatures as methane - a potent driver of global warming - escapes thawing permafrost.

That has scientists quietly planning for the unthinkable - from drowned coastal cities to global average temperatures that could soar 5-8 degrees Celsius (8-14 Fahrenheit) over 20 years, causing food system collapse and displacing billions of people.

"Extreme climate change risks are under-explored," Luke Kemp, a researcher with the Centre for the Study of Existential Risk at the University of Cambridge, warned at a pioneering conference last week, where scientists sat in stunned silence during a frank assessment of looming threats.

But "positive" climate change tipping points - where small changes accumulate into irreversible, self-sustaining big changes - may also be on the horizon.

These include a switch to solar and wind energy as those two power sources become cheaper than fossil fuel alternatives, and, in some countries, a decline in meat-eating - a major driver of global deforestation and climate change - as tasty and affordable alternatives become available.

How do such big changes happen?

Scarlett Benson, of the Food and Land Use Coalition, says moving away from meat, for example, depends on things such as price (it it cheaper?), performance (does it taste good?), accessibility (can you get it at the local shop?), culture (are your friends and family also switching?) and capability (do you know how to cook it?). Smart public policy can then help accelerate change.

Social tipping points may also be emerging, from graduates refusing jobs at unsustainable firms to families investing in solar panels, eating less meat or joining climate change protests when they see their friends and neighbours doing it.

"Tipping happens not because all see the light at once but because we’re influenced by opinions of others," said W. Brian Arthur, a California economist who works on complexity theory.

Tim Lenton, director of the Global Systems Institute at the University of Exeter and a researcher on "positive" tipping points, calls them critical to driving the needed climate action fast enough.

"I think our best, and possibly last, hope of avoiding the bad tipping points is finding and triggering some good tipping points," he said.

In Iraq, it's a lack of action altogether that's driving problems.

Tens of billions of dollars in oil revenue are swelling the nation's coffers as global fossil fuel prices rise - but the lack of a functioning government for almost a year means little is being spent on protecting the nation against worsening climate impacts including drought, water shortages and soaring heatwaves, writes correspondent Nazih Osseiran.

With political wrangling still ongoing about who should lead the country after elections last October, "the political crisis is adding a layer of complexity to the climate crisis in the country," says Zeinab Shuker, an Iraqi sociology professor. As a result, "the worst-case scenario is what is happening right now."

See you next week,

Laurie

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