Edited sentence: A century after the end of World War I, in 2018, humanity appeared to greet international and U.As the 21st century continued to unfold, humanity was woefully slow to adjust to urgent new circumstances.At risk is a planet, possibly unique in the Milky Way galaxy, which is underappreciated by Earth's most intelligent and destructive species.Countries and non-state groups incorrigibly continued their aggressions against their planetary neighbors, in the face of common existential threats, most prominently the multifarious disasters stemming from global warming.During the 20th century, no effective steps had been taken to prevent World Wars I and II, despite prescient warnings, not least by the aggressors themselves.national warnings of the global-warming threat with consternation or apathy