If you needed further signs that humans are likely warming the planet, you just got it. NASA and NOAA have independently determined that Earth surface temperatures in 2015 were the hottest since record-keeping began in 1880, beating the 2014 average (the previous record) by a sizeable 0.13 degrees Celsius. Most of the on-record warming happened within the past 35 years, too. And you can't pin this on weather patterns like El Niño. While those conditions certainly contributed to 2015's higher temperatures, it was the "cumulative effect" of decades of warming that led to the new high.