Suggestions for non-fiction books about the decay and decline of human civilisation?

Sorry, this chain made me cynical and sad about political discussion on this forum.

To recap:

1. Just because human society has perhaps, on the whole, improved doesn't mean that we don't have significant problems we have to address yet right on our collective doorstep. To suggest that saying we're the best we've ever been means we have nothing left to achieve misinterprets Pinker's argument (and this is coming from someone who doesn't really find Pinker's claims in this book particularly compelling).
2. How human society reacts, locally and globally, to these looming issues is far from predetermined, and assuming that it will necessarily lead to chaos and self-disillusion is both defeatist and counterproductive to waht I assume CPriest's goals are (that is, trying to increase people's desire to address human driven global warming).
3. The entire premise of this thread, non-fiction books about Human civilization and decay must in some sense be fanciful because of the fact that human civilization, as a whole, has not yet in fact decayed or declined. The Modern Era(TM) is in a state of flux, and so it may seem like "decay" if you expect the world to always stay the same no matter what, but it doesn't so ...
4. the only books that can be recommended are not worth reading (i.e., probably quite questionable) or are histories of periods so long ago that the record supporting their narratives is sorely under-resourced and leaves far too much unknown and unaddressed to be particular useful for what I can infer is the OP's interest here.

The sorry was to you because you tried to offer some challenge to the OP. Most of this is in response to the OP.

You are correct that we don't know for sure what will happen or how, in response to anthropogenic climate change. I want to take a moment and paint a picture on how "catastrophic breakdown of organized society" could happen, and how real of a possibility it is. So how could this happen? Well we need to look at the various effects global mean temperature increase will have, and their secondary consequences therein.

Crop Failure

As mean temperatures increase, habitable zones for crops will shift or disappear. Staple crops that have grown in areas for centuries will become inviable.

• " For the top four maize-exporting countries, which account for 87% of global maize exports, the probability that they have simultaneous production losses greater than 10% in any given year is presently virtually zero, but it increases to 7% under 2 °C warming and 86% under 4 °C warming.".
• Another staple crop, rice, is also being impacted. "Grain yield declined by 10% for each 1°C increase in growing-season minimum temperature in the dry season, whereas the effect of maximum temperature on crop yield was insignificant. This report provides a direct evidence of decreased rice yields from increased nighttime temperature associated with global warming."
• Crop failure leads to collapsed economies, collapsed industries, and starvation. Refugees fleeing stricken areas will be common and number in the millions.

Sea Level Rise

Global ice reserves, ice caps, glaciers and polar ice are melting at an increasing rate. The total sea level rise is still heavily debated in the scientific community, but to get an idea of what varying amounts of sea level rise would look like you can use this tool from NOAA. According to the United Nation’s Intergovernmental Panel on Climate Change, sea levels will at the least rise by 0.29m and at most 1.1m. Many in the scientific community see this as a conservative estimate, reports from NOAA and The National Academy of Sciences suggest more drastic increases. Another report from NOAA predicts that there will be intense variation in sea level rise based on location, as much as 30%, based on various factors. OK, the oceans are rising, so what? Well here's what:

• We very well could lose 691,120 sq miles of coastal and low lying land to rising sea levels.
• The IPCC report estimates that 187 million people will be directly impacted by rising sea levels, this creates climate refugees.
• We are losing low lying islands and atolls to sea level rise already, by 2100, Maldives will be completely uninhabitable; this creates climate refugees.
• "According to the Internal Displacement Monitoring Centre, there were 18.8 million new disaster-related internal displacements recorded in 2017."
• “In the absence of adaptation, more intense and frequent extreme sea level events, together with trends in coastal development will increase expected annual flood damages by 2-3 orders of magnitude by 2100.” This means areas that are not over taken immediately are now going to be more prone to flooding events like tsunamis, storm surge, etc.
• Ecosystem collapse could be a category all on its own. In relation to sea level rise: Erosion of beaches and coastal lands, salinization of soils and farmlands , and saltwater intrusion into aquifers used for drinking water are all problems we’re starting to see and will grow in the future... ...The salinity of freshwater rivers and wetlands may increase."

Increase in Weather Extremes

When talking about Climate Change, we discuss increases in mean temperatures to the tenth decimal. Tiny increases in temperature will cause massive impact, but in some areas temperatures will increase so much as to make them uninhabitable for humans and other wildlife. In others, the magnitude and frequency of severe weather including hail, tornadoes and tropical storms will all increase.

• Areas of the tropics and the middle east will (and are) experience ever increasing record temperatures, even with a conservative estimate of 2c increase in mean temperature.
• "More than 90 percent of the excess heat absorbed by the climate system due to human-caused greenhouse gas warming is stored in the ocean...", this in turn leads to increase water temperatures. Hurricanes thrive over warm waters.
• In general, frequency and intensity of tropical cyclones is increasing due to climate change.

Connecting the Dots

Honestly, I can see any one of the several direct impacts of anthropological climate change causing major societal disorder, economic and governmental collapse, and geopolitical instability.

• Massive refugee crises lead to strained tension already inflamed by the recent rise of populist, nationalist regimes.
• Depletion of food resources during crop failure will lead to starvation, and geopolitical strife. World trade between major food producers will become ever more important in an increasingly distant economic community. Uprisings will be common in less-than-stable nations, this predicates a possible return to colonialist ambitions in the search for decreasing resources.
• In a similar vein, when the aforementioned island nations are completely submerged, their sovereignty is dissolved according to international law. The resources remaining will be prime for the taking, and world powers will all want their piece.
• We are already seeing geopolitical saber rattling regarding new resources opening up in the arctic circle. Areas that were previously encased in ice have opened up, offering new shipping routes and access to oil and natural gas.

Conclusion

There are a lot of other direct, secondary and indirect effects of anthropogenic climate change I haven't listed here. These are just the big ones that come to mind right now. As I stated before, in my personal opinion I believe climate change will create catastrophes that test the endurance of humanity as it is now. We must take immediate, drastic action to avoid such results. Some experts say that some of this is now unavoidable, I tend to agree.

Sorry @cpriest, I kind of hijacked this thread, hope you don't mind. I'm super passionate about this stuff and felt the need to contribute a bit. I tried not to write an entire book, but if I did, I'd recommend it in your thread.