Jeff Sturgeon's Last Cities of Earth

2091—The Year the Earth Changed As Yellowstone erupts, sending humankind into an extinction-level event, countries, cities, and enclaves of the elites create desperate, innovative ways to survive the coming ice age. Some scientists uplift entire cities into the sky above the disaster, others build undersea colonies, while some look to space. A few delve into the darkness of genetic modification and try to evolve a new species of humanity. Now, over two centuries have passed since the day that changed the world. Many global trade routes have resumed, and it is an age of discovery ... and danger. Brave airship crews explore the sky wilderness between the aerial metropolises, connecting more of the floating cities. Threats lurk in the skies as well as the ruins scattered around the world like half-forgotten memories. These are the last cities of Earth.