The mechanism follows from climate disruption. As the tropics become uninhabitable and/or unfarmable, millions will migrate (mostly) north, crossing borders and driving fascist / jingoist governments into power. (We see this beginning already.) Global war follows, disrupting all kinds of global trade, shattering supply chains. Famine ensues, and more war.
Preventing this requires preparation to absorb millions of refugees, and food aid to places not entirely uninhabitable. Temperate agriculture will be badly disrupted too, so we also need mass agriculture less dependent on clement conditions.
The mechanism follows from climate disruption. As the tropics become uninhabitable and/or unfarmable, millions will migrate (mostly) north, crossing borders and driving fascist / jingoist governments into power. (We see this beginning already.) Global war follows, disrupting all kinds of global trade, shattering supply chains. Famine ensues, and more war.
Preventing this requires preparation to absorb millions of refugees, and food aid to places not entirely uninhabitable. Temperate agriculture will be badly disrupted too, so we also need mass agriculture less dependent on clement conditions.