One of America’s leading scientists has dismissed as “raving nonsense” the pope’s call for action on climate change – so long as the leader of the world’s 1 billion Catholics rejects the need for population control.

In a commentary in the journal Nature Climate Change, Paul Ehrlich, a senior fellow at the Stanford Woods Institute for the Environment, argues that Pope Francis is simply wrong in trying to fight climate change without also addressing the additional strain on global resources from population rise. “That’s raving nonsense,” Ehrlich told the Guardian. “He is right on some things but he is just dead wrong on that.”

The critique in “Society and the Pope’s encyclical”, part of a special package from scientists on the encyclical, marked a rare note of dissent from scientists and campaigners. Many hope that the pope will drive home his call to action on poverty and the environment in his speech to Congress on Thursday.

Ehrlich, in his Nature Climate Change commentary, accuses Francis of a dangerous flaw in his indictment of consumerism and its effects on the poor and the environment. The pope had fallen for the usual clerical “obsession” with contraception and abortion – when he could have instead broken new ground on the Catholic church’s approaches to women’s reproductive rights and family planning.

The broadside exposes some of the difficulties of embracing a figure such as the pope – for those on the left as well as the right.

Conservative allies of the pope, on issues such as same-sex marriage and abortion, have balked at his denunciation of capitalism and call to action on climate change.

Those thrilled by the pope’s intervention on climate change – and Ehrlich counts himself among them – were troubled by Francis’s refusal to countenance the need to limit population, the scientist said. “It is crystal clear. No one concerned with the state of the planet and the state of the global economy can avoid dealing with population. It is the elephant in the room,” he said.

Ehrlich became a household name in the US nearly 50 years ago for warning of a global catastrophe because of population growth – a scenario he later conceded did not entirely materialise.

But while the scientist applauded the pope’s overall message on the environment, he said Francis had undermined his own cause by failing to acknowledge the need for birth control and reproductive choice.

Indeed, Francis in the encyclical explicitly rejects the idea of population growth as a strain on global resources. “Demographic growth is fully compatible with an integral and shared development,” the pope wrote. “To blame population growth instead of extreme and selective consumerism on the part of some, is one way of refusing to face the issues.”

Ehrlich said that was a mistake. The global population, now over 7 billion, is projected to reach 9.7 billion in 2050 according to the United Nations. “There is no competent scientist who would say there is not a problem with population growth. In other words, the pope is dead wrong. Here he is following an antique doctrine that it is impossible to change,” Ehrlich said. “I am sure he knows better, he is not a dope.”

Other scientists in the Nature Climate Change package also took issue with the pope’s message – such as his call for leaders to undergo a “moral conversion” when it came to the environment. That overlooked the powerful forces behind the global economic order, and fell far short of a credible strategy, writes Erik Olin Wright, a sociologist at the University of Wisconsin at Madison.

“The powerful interests that are opposed to genuinely restoring ecological balance and seriously dealing with global poverty need to be defeated through political confrontation, rather than simply converted to a more compassionate, ethically grounded mindset.”