Penn State professor of meteorology Michael E. Mann warned a congressional subcommittee of the dangers of climate change at a hearing on natural disaster preparedness Tuesday.

Representative Harley Rouda of California, who serves as the chairman of the Subcommittee on the Environment of the House Committee on Oversight and Reform, called the hearing to examine governmental response plans for natural disasters. Mann and several other witnesses testified on the escalating frequency of increasingly intense natural disasters and how this trend is related to climate change.

Mann, who has written four books on climate change and has received dozens of awards for his research and environmental activism, described his research on extreme weather events to the committee in his opening statement.

“We’re using the term natural disasters, but in many cases, there is absolutely nothing natural about the disasters we are talking about,” he said. “We’re not saying they’ve been caused by climate change, we’re saying climate change has worsened them.”

Mann then focused on the role of rising sea levels and warmer air temperatures in producing more intense hurricanes. He cited devastating recent storms such as Hurricanes Micheal, Maria, and Irma.

Dr. Michael E. Mann, a professor of atmospheric science and director of the @Penn_State Earth System Science Center, issued a grave warning about #ClimateChange's effect on natural disasters. Watch our @OversightDems hearing LIVE https://t.co/ewDiIw2wZ6 pic.twitter.com/E2F3TRkeF9

— Archived: Rep. Harley Rouda (@RepHarley) June 25, 2019

Mann and his fellow witnesses — among them the president of the climate forecast applications network and the former director of the Federal Emergency Management Agency — then answered questions from representatives.

He was quick to point out inconsistencies in the testimony of his fellow witnesses and the claims of several committee members, specifically regarding growing wildfires and the geological record left behind by hurricanes. He also countered claims that modern climate change can be attributed to natural changes in the Earth’s atmosphere.

“It’s not a real oscillation,” he said of changing climate statistics. “It’s the irregularity of our impact.”