1.5C is an arbitrary figure. There is no guarantee that this is a "safe" level of global heating, below the threshold between one climatic state and another. It could be 1.383C. Or 1.649C. Because these are highly complex systems, we have no idea where the tipping point lies.
The transition, when it comes, is likely to be abrupt and drastic - this is what has happened in the past. Complex systems seek equilibirum. When they are knocked out of one stable state, they flip into another, often entirely different state.
The different state could be inimical to human life, and many of the other lifeforms with which we share the planet, which, like us, have evolved to survive the current climate.
The ony honest answer is that we have *no idea* of where the threshold lies. We cannot compute the full range of feedbacks between atmosphere, oceans, terrestrial carbon sinks and biotic responses.
All we can say is that any gradual increment in temperature rise could be the last, before sudden, cascading #ClimateBreakdown occurs. So what does this mean for policy?
It means we must treat the threat of irreversible climate breakdown as a global emergency, with immediate and drastic measures to leave fossil fuels in the ground, get livestock off the land, allow the rapid drawdown of carbon through reforestation.
In other words, to allow the systemic healing mechanisms, that maintain the current climatic equilibrium, to kick in. The overwhelming priority for human welfare is a Marshall-scale plan for the planet. But no government is yet committed to this.
This is why the work of 350.org, @ExtinctionR and other rebels against inaction is crucial. Society is like an amoeba: it moves from the margins, not from the centre. Government will not lead this change. But we can.
Join @ExtinctionR in London and other cities tomorrow. I'll be there. Will you? rebellion.earth
