While there were more sci-fi films than the year prior, there still weren't many in 1961. Yet, even with a small sample there were two dominant themes. There were three movies that featured Captain Nemo to varying degrees. There were three films which featured a global warming disaster. Since all came from different sources, it makes an intriguing coincidence.
Konga -- A scientist discovers a plant growth hormone that works on animals. He uses it to make a chimp into a gorilla to silence his enemies.
Master of the World -- Two of Jules Verne's novels are blended to produce one story about the rogue genius and peacenik: Robur.
Atlantis: The Lost Continent -- A greek fisherman returns a lost princess to Atlantis but becomes embroiled in palace intrigue and a plot for Atlantis to rule the world.
The Day the Earth Caught Fire -- Nuclear weapons tests bump earth into a decaying orbit into the sun. Oppressive heat, fires, riots. Can similar blasts move earth back into proper orbit?
Voyage to the Bottom of the Sea -- Admiral Nelson, aboard his super-sub "Seaview" must race against balking bureaucrats and on-board saboteurs to save the earth from the burning Van Allen belts.
The Day the Sky Exploded -- English dubbed version of '59 italian film. An errant atomic rocket causes a giant asteroid to head for earth. It's approach causes climate disasters and oppressive heat. Are earth's nuclear missiles enough to stop it?
The Phantom Planet -- An astronaut lands on a mysterious asteroid to find miniature people. He is told he can never return, lest their secret existence be compromised.
Assignment: Outer Space -- A reporter is attached to a routine space mission, which becomes a desperate race to save the earth from a deadly rogue spaceship.
Mysterious Island -- Jules Verne's story of Civil War soldiers cast away on a remote island with giant animals and Captain Nemo. Can they escape a pirate attack and exploding volcano?
The Giant of Metropolis -- Italian film about a leader of Atlantis who seeks to transplant the brain of his father into his son's head, so he can rule forever, runs afoul of "the gods."
The Beast of Yucca Flats -- More of an atomic angst film than sci-fi. Tor Johnson becomes a killing brute after exposed to an atomic test.
Rocket Attack: USA -- Another atomic angst film, not really sci-fi. Low-budget spy drama where the Russian's launch a nuke at New York.
Valley of the Dragons -- Loosely based on a Jules Verne tale. Two men about to fight a duel are swept up by a comet, which is inhabited by cavemen and dinosaurs.
The Most Dangerous Man Alive -- A criminal, framed by his cohorts, escapes onto a nuclear test site. The blast makes him invincible. Revenge ensues.