Apart from looking at planets and determining whether or not they belong in our solar system (welcome back, Pluto), NASA also gathers data on the Earth. They have found that the average temperature on the planet was 1.04°C warmer than the average of all the previous Octobers. You can see NASA's analysis data here. This was the biggest variance for any month from an average since Nasa started collecting data in 1880.
The temperature around the world in the month of October 2015.
So the world is warming up, but why? The biggest reason is human-caused global warming, like the greenhouse gas effect from carbon dioxide or methane from cattles. El Niño is increasing the intensity of our effect on the planet. In fact, 2014 was the warmest year in modern record.
It is undeniable, global warming is happening.