"If there is enough awareness among the public, governments won't have to impose taxes. But it's something we should think about seriously," Pachauri said.
Their comments on Thursday come just days before world leaders sit down for a UN climate conference in the Danish capital in an attempt to forge a new deal aimed at cutting carbon emissions.
McCartney is pushing a 'Meat-Free Mondays' campaign, aimed at encouraging people to cut down on their consumption.
"Our campaign says 'try one meat-free day in the week'," he said.
"It's very do-able. If you say to people, 'go vegetarian,' that's very hard to do.
"But if you suggest to people 'one day,' I think most people will have a bit of a blow-out over the weekend and Monday they go to the gym.
"Once, for instance, we didn't recycle - we weren't interested, but now it's an accepted part of our lifestyles."
Lasse Brun, from Compassion in World Farming, an animal welfare charity, told Al Jazeera he was pleased meat was being targetted by environmental activists.
"To feed and fuel the world by 2050, where we are predicted to have 9.2 billion people, business as usual is simply not an option.
"We've commissioned a study with Friends of the Earth which shows whether we can feed and fuel the world sustainably and humanely by 2050.
"And all we need to do, in the developed world, is cut down on meat consumption just a little bit - two or three times a weeks ... and that would allow for the developing countries to increase their diary and meat consumption to a sustainable level globally.
He added that sustainable farming is more likely to benefit small communities and livelihoods than the mass market model currently being used to feed populations.
Earlier, Pachauri met with Jose Manuel Barroso, the European Commission president, who said even if next week's global climate conference does not yield a final accord it must "light the pathway to a legal agreement" on reducing greenhouse gas emissions.