Let's say there's a pandemic. This causes a huge increase in medical care expenses, R&D expenses to bring tests, treatments and preventatives to the market, followed by manufacturing, distribution, and administering the medicine, PPEs, etc.
It further causes increased funerary costs, income gaps from sickness, lockdowns, and deaths, manufacturing and distribution shortages that cause inflation, loss of productivity including non-fungible labor losses like agriculture.
All that money was created out of thin air in rich countries, driving debt and inflation; the expenses fall on the poor in most of the world and are mostly the latter.
Solution: tax the rich. This pays for the pandemic costs without driving inflation.
Suppose somebody starts a war. This burns a lot of fuel, explodes a lot of ammunition, requires a lot of soldiers who have to be fed and clothed, destroys a lot of expensive hardware, infrastructure, residences, disrupts lives, income and productivity and REALLY impacts global supply chains. People in rich countries can't afford fuel for their hyper-consuming lifestyles (not necessarily a bad thing, we need to stop burning), and poor people can't afford food nor fuel. (OK, so this helps with the exploding population bomb), but still the answer is the same:
TAX THE RICH!
Now about the BIG EXISTENTIAL CRISIS: Climate Change.
It is already costing the world more in the climate related damage to food supply, forests, oceans, life, health, property damage, than the cost of making the transition to MORE EFFICIENT LIFESTYLE based on 'more renewable' sources - that is, creating the absolutely necessary shift to car-free, plane-free, ship-free, meat-free, fish-free life and eliminating chemical fertilizer based, mechanized agriculture.
Here is the BIG, DIRTY SECRET: in a sustainable world, there is no way to amass nor hold wealth. All capitalist enterprises cause more environmental damage than the profits - all economic equations fall apart when you include the cost to the environment. Wealthy lifestyles have to be eliminated, and the fastest way to do this is:
TAX THE RICH!
Also in US, a Congress of millionaires has been bleeding the middle class, militarizing the justice system, legalizing financial fraud and political corruption, escalating the financial barriers to entry into government, eroding individual rights, consolidating the media, and starving public services of funds in an attempt to justify privatization, with collusion from both sides of the aisle since Reagan was elected. Solution:
TAX THE RICH!