The head of the Berkeley Earth Surface Temperature (BEST) study, Richard Muller, a Berkeley physicist previously known for his skeptical views on anthropogenic warming, appeared on Capitol Hill Monday, for the first time since the release of the study’s results.

As we’ve reported, the study found that the Earth is warming. Surface temperatures have increased about one degree Celsius since the mid 1950s, according to the study, which relied on a database of 1.6 billion records.

According to a report from AFP, Muller told lawmakers that he no longer doubts that global warming is real and caused by humans.  However, the extent of human influence remains uncertain, he reportedly said.

This animation shows the Muller’s team’s analysis of the Earth’s surface temperature changes since 1800: