One of the U.S. Energy Department's key roles is to develop ways to reduce carbon dioxide emissions — the leading driver of human-caused climate change. Yet the agency's top official doesn't think carbon is all that big of a problem.

Energy Secretary Rick Perry on Monday repeated his long-held position that carbon emissions are not primarily responsible for global warming. Rather, the "most likely the primary control knob is the ocean waters and this environment that we live in," he said in an interview on CNBC's Squawk Box.

"The fact is this shouldn't be a debate about, 'Is the climate changing, is man having an effect on it?' Yeah, we are," Perry added. "The question should be just how much, and what are the policy changes that we need to make to effect that?"

The interview evoked a sense of climate denial déjà vu.

Scott Pruitt, the head of the Environmental Protection Agency, went on Squawk Box in March and similarly said he doesn't believe that human-caused buildup in atmospheric carbon concentrations is the primary contributor to global warming.

Asked if he believed carbon was the "primary control knob" for climate change, Pruitt replied that he "would not agree that it's a primary contributor to the global warming that we see."

Image: ed hawkins

Contrary to what Perry and Pruitt say, however, climate scientists in the U.S. and globally agree that human influence is the dominant cause of global temperature rise since the mid-20th century. The burning of fossil fuels, along with the destruction of forests and clearing of farmland, has dramatically boosted atmospheric concentrations of greenhouse gases over the last century.

Carbon in particular is "the single most important climate-relevant greenhouse gas in Earth's atmosphere," NASA scientists wrote in a 2010 study.

Their paper, titled "Atmospheric CO2: Principal Control Knob Governing Earth’s Temperature," apparently coined the phrase that CNBC and members of the Trump administration frequently use when discussing climate science, noted Gavin Schmidt, a co-author and climate modeler at the NASA Goddard Institute for Space Studies.

TFW the title of a science paper you co-wrote becomes a litmus test for understanding climate change. 🤔 https://t.co/rPQhPqey0k — Gavin Schmidt (@ClimateOfGavin) June 19, 2017

Carbon dioxide levels are now above 400 parts per million (ppm), up from the preindustrial level of about 280 ppm.

This rise has driven an increase in the planet's surface temperature, putting the Earth on a dangerous path, according to U.S. climate scientists.

Since the start of this century, annual global temperature records have been broken five times — in 2005, 2010, 2014, 2015, and 2016, with last year exceeding all previous years since instrument records began 137 years ago, both NASA and the National Oceanic and Atmospheric Administration (NOAA) reported earlier this year.

Image: bob al-greene/mashable

Perry's anti-science comments come at a particularly uncertain time for the Energy Department.

The agency is closing its Office of International Climate and Technology, which works with other countries to develop clean energy technologies, the New York Times reported last week. Under the White House budget proposal for fiscal year 2018, the department's Office of Energy Efficiency and Renewable Energy would get only $636 million in new funding — a staggering 70 percent drop from the previous year.

In the Squawk Box interview, Perry bristled at the notion that rejecting the mainstream scientific consensus on climate change would put someone on the wrong side of history.

Being a climate change denier is "quite all right," he told CNBC, suggesting that skepticism is a sign of a "wise, intellectually engaged person."