With 2015 officially recognized as the hottest year on record, climate scientists believe it is getting increasingly harder to point to any culprit that is not climate change.

According to The Washington Post, only once in the past decade has the record for hottest year not been broken. Past studies have given the chances that this trend is not manmade at an alarming one in 650 million.

The new study, published in the journal Nature Scientific Reports, backs up those findings.

"The press reports last year about the unlikely nature of recent global temperature records raised some very interesting questions, but the scientists quoted hadn't done a rigorous calculation," study lead author Michael Mann, distinguished professor of meteorology and director at Pennsylvania State University, said in a press release. "As a result, the probabilities reported for observing the recent runs of record temperature by chance alone were far lower than what we suspected the true probabilities are. "

Research that has tried to link climate change to natural factors pointed to a mysterious "hiatus" in which the globe's average temperature leveled off for a time. But researchers recently disproved that theory by identifying accelerated warming deep in the world's oceans.

"Natural climate variability causes temperatures to wax and wane over a period of several years, rather than varying erratically from one year to the next," Mann said. "We provided a method for doing this based on combining information from state-of-the-art climate model simulations with the observational temperature record, and we used this method to estimate the probabilities correctly."