Frustratingly, many people still don’t grasp what the unfolding climate and ecological crisis really means for the current generation and today’s children, and what’s being done about it (or, more accurately, not done).

Greta Thunberg stated very clearly something that gives me a great deal of anxiety, and what I think all the parents should have at the forefront of their minds:

“Some of you may have heard that we have 12 years as from 1 January 2018 to cut our emissions of carbon dioxide in half. But I guess that hardly any of you have heard that there is a 50 per cent chance of staying below a 1.5 degree Celsius of global temperature rise above pre-industrial levels. Fifty per cent chance.

And these current, best available scientific calculations do not include non-linear tipping points as well as most unforeseen feedback loops like the extremely powerful methane gas escaping from rapidly thawing arctic permafrost. Or already locked in warming hidden by toxic air pollution. Or the aspect of equity and climate justice.

So a 50 per cent chance – a statistical flip of a coin – will most definitely not be enough. That would be impossible to morally defend. Would anyone of you step onto a plane if you knew it had more than a 50 per cent chance of crashing? More to the point: would you put your children on that flight?”

(She also gave a speech to the UN a couple of days ago.)

So the most ambitious target that’s even talked about (but not in any way worked on) is in fact a dangerous gamble. And of course, the reality is that the world is moving in the opposite direction while the ineffectual talk continues: emissions are still rising, and nobody knows when they will stop rising.

So what is the “crash” Greta talks about? Heating could reach 2.5 or even 3.5 degrees, which would unravel human civilisation and destroy much of the natural world, in combination with the biodiversity crisis that’s also unfolding as a result of human actions.

What will things look like once we go beyond 1.5 degrees of heating? Let me point out a few projections:

• Crop yields are already dropping (20-40% drop expected for corn at 2-4º heating), nutrition levels in crops fall as CO2 levels increase, and the risk of multi-breadbasket failure is going up. (Multi-breadbasket failure means simultaneous crop failure in two or more regions of the world.) At two degrees heating, the risk of multi-breadbasket failure for maize is 54%. Wheat and soybean are similarly affected. That means famine.

• A third of the world’s topsoil is already degraded, and the rest could be gone within 60 years. By 2050, 4 billion people will be living in drylands. That means famine.

• We are at the start of the sixth mass extinction. 200 species are going extinct every day, and 1 million species are at risk of extinction, many within decades. That’s out of approx. 9 million species on Earth, so it means…collapse of life on the planet? Can any ecosystems survive this rate of extinction? I don’t think anybody knows. Should we be doing everything we can to avoid finding out?

• There will be hundreds of millions of climate refugees. Conservatively, World Bank expects 140 million by 2050. IPBES estimates between 50 and 700 million displaced people by 2050. Where will they go? What kind of conflicts will be produced?

• Extreme weather (wildfires, floods, hurricanes) will keep getting worse. For example, in Australia, the accumulated loss of wealth could reach $211 billion by 2050 and $4 trillion by 2100. This means destruction and impoverishment around the world.

• Two thirds of glaciers in the Himalayas will disappear by the end of the century (one third is actually going to melt no matter what action is taken on climate). This directly affects 1.6 billion people. For some of them, it will mean no more water at all. That means, again, famine, displacement and conflict.

• In New Zealand, where I live, at least $8 billion of council infrastructure is at risk of sea level rise by 2100 (using conservative sea level rise projections). This doesn’t include highways, homes, businesses, office buildings, hospitals, factories and schools, which the Insurance Council estimates to be tens of billions more: at 1m sea level rise, 125,000 buildings worth $38 billion are at risk. 700,000 people and $135 billion worth of property, as well as 19,000km of roads, 1500km of railway and 20 airports are already exposed to flooding from rivers in extreme weather. These are huge numbers for a small country like ours. Combine this with drought, wildfires, and collapse of the insurance industry, and it means that people in New Zealand will be impoverished. The situation is unlikely to be better anywhere else.

• Nearly 2.4m of sea level rise by 2100 cannot be ruled out (and 1.1m is most certainly going to happen). This will inundate many coastal cities, destroying vast amounts of wealth and forcing migration. But even prior to that, extreme sea level events that used to occur once a century “are projected to occur at least once per year at many locations by 2050 in all scenarios.”

This is just a sample of the projections, and none of these are really worst cases. For example, for sea level rise, this article contains a staggering paragraph:

“The IPCC considers the likely range of sea level rise but not the worst-case scenario. Recent expert analysis led by Bamber concluded that up to 238cm of sea level rise remains possible by 2100, drowning many megacities around the world. “This cannot be ruled out,” said Zita Sebesvari at the United Nations University, a lead author of the IPCC report.”

So the IPCC looks at “likely” scenarios, not all of them (and keep in mind that its reports are created in the context of huge political pressure). In other words, there’s an overwhelming tendency to present an overly optimistic picture of where we’re headed, starting from the IPCC, and flowing into the media, political speeches etc.

For an unvarnished view, you can read this paper called Deep Adaptation. As the author himself points out, the future outlined in the paper isn’t definite, but it’s certainly a possible one. When it comes to existential risks, should the world be acting only on the “likely” scenario, or on the lower-probability-but-still-possible worse scenarios? It seems obvious that acting on optimistic projections is foolish when faced with existential threats.

Finally, here’s the kicker: all of this will happen during our children’s lifetimes. A child born today should be reasonably expected to live past the end of the century. Even young adults will get to experience utterly catastrophic consequences of climate inaction in the second half of this century.