Joe Strummer was a remarkably well-read and politically engaged rock star. His lyrics were full of references to things going on in the world, and "London Calling" is no different. Strummer tapped into fears of oil depletion and climate change long before these issues penetrated mass consciousness. The line, "engines stop runnin'" is clearly indicative of an oil shortage, a nod to the oil shocks of 1973 and 1979 that left the West out of gas while OPEC, the Organization of Petroleum Exporting Countries, inflated oil prices. Surprisingly, though, Strummer's understanding of the oil crisis may have extended beyond the OPEC boycott to the concept of peak oil, which has only become the subject of intense discussion much more recently. In an interview with NME, he declared, "There's ten thousand days of oil left. It's finite." That's true; the only question is how long the oil supply will last before the world taps out this vital resource.
Climate change is addressed too, but not in the way you might think. Today most scientists believe that the world is going through a trend of warming, but in the 1970s that trend was only beginning to become apparent. In the 1960s and 50s, data actually suggested that the world was headed towards a period of cooling! This might explain Strummer's insistence that "the ice age is coming," or the pure ambivalence of this statement considering that the next words are "the sun's zooming in" - maybe causing warming or maybe just blowing up. Whether too cold or too hot, there's no question that the world described in "London Calling" is anything but just right.
Meanwhile, the partial meltdown of a nuclear power plant at Three Mile Island, Pennsylvania in early 1979 turned the tables on the popular opinion of nuclear energy, sparking new fears of nuclear catastrophe throughout the world. At the same time, "there was a lot of Cold War nonsense going on," according to Strummer, raising the specter of deliberate use of nuclear weapons to achieve military aims. The fear of nuclear holocaust creeps into "London Calling" with references to "meltdowns expected" and "a nuclear error."
Joe continued to explain in the NME interview that he was inspired to write "London Calling" while riding in a cab with a woman alongside the River Thames, the river which flows through central London. "We already knew London was susceptible to flooding. She told me to write something about that. So I sat in the front room, looking out at Edith Grove." The irony of the lyric, "London is drowning and I live by the river": Joe Strummer really did live practically right next to the river, living at World's End Estate, Chelsea SW10.
The culture of the time finds its way into "London Calling" as well. Punk was still huge in 1979, but it was an altogether different beast than it had been a few years earlier. Many of the original punk bands had split up, and The Clash were one of the few successful bands left (if you could even consider their later music to be punk). The general feel was that by 1978, "real punk" had died as a movement. With the involvement of the recording industry, punk was becoming very commercial, and many imitators were on the rise. Strummer notes this, with a line dedicated to "the imitation zone": "Forget it, brother, you can go it alone!" The larger milieu of the 1970s, its superficiality and lack of substance, gets a line as well. Strummer denounces all the "phoney Beatlemania," either surrounding The Clash itself or the Broadway musical Beatlemania, which offered "Not the Beatles, but an incredible simulation," as one ad ran. There was a sense in the 1970s that people didn't care so much about creating an authentic new culture for the new generation. Instead they wanted to relive the 1960s, branding new bands as the new Dylan, the next Beatles.
To The Clash, all of this felt like the apocalypse. Everything was falling apart to Strummer, which you can hear in the final line of the song, "I never felt so much a-like..." which, as live versions of the song prove, is a shortened version of the full line, "I never felt so much a-like singin' the blues."