He's a 42-year-old freshman senator, but when asked by Jonathan Karl on "This Week" if he's ready to be president, Republican Sen. Marco Rubio of Florida answered without hesitation.

"I do … but I think that's true for multiple other people that would want to run … I mean, I'll be 43 this month, but the other thing that perhaps people don't realize, I've served now in public office for the better part of 14 years," said Rubio. "Most importantly, I think a president has to have a clear vision of where the country needs to go and clear ideas about how to get it there and I think we're very blessed in our party to have a number of people that fit that criteria."

When asked if he was qualified to run, Rubio reiterated that the Republican Party has several qualified candidates.

"The question is what - whose vision is the one that our party wants to follow?" he said.

Rubio - who spoke to Karl on Friday in New Hampshire - said that if he decides to seek the presidency, he would not simultaneously seek re-election as a senator for the Sunshine State.

"I believe that if you want to be president of the United States, you run for president," he said. "You don't run for president with some eject button in the cockpit that allows you to go on an exit ramp if it doesn't work out."

The Florida senator - who was once considered a 2016 Republican front runner - has seen his star fade in recent days, according to at least one recent New Hampshire poll. But Rubio seems to take it in stride, telling ABC News that polls are not something he pays a great deal of attention to, even joking that he has been jinxed after gracing the cover of TIME magazine.

"It's probably the 'TIME' cover jinx, just like the 'Sports Illustrated' jinx," he said. "If you decide to run for president, there's going to be a campaign and in that campaign, you're going to interact with voters and you're going to explain to them where you stand and - and those numbers can change one way or the other."

Sen. Marco Rubio Gives Hillary Clinton an "F" as Secretary of State

During the interview with Karl, Rubio took aim at former Secretary of State Hillary Clinton, who is seen by many as the strongest Democratic candidate for president in 2016. Rubio said he was sure Clinton would highlight her time at the State Department as a positive should she seek the White House, but he offered a much more negative view of her tenure at Foggy Bottom.

"I'm sure she's going to go out bragging about her time in the State Department. She's also going to have to be held accountable for its failures, whether it's the failed reset with Russia or the failure in Benghazi that actually cost lives," he said.

Rubio said he didn't think Clinton deserved a passing grade for her time at the State Department, saying he thought she earned an "F."

"If you look at the diplomacy that was pursued in her time in the State Department, it has failed everywhere in the world," Rubio said. "If she is going to run on her record as secretary of state, she's also going to have to answer for its massive failures,"

Sen. Marco Rubio Expresses Skepticism Over Ability to Reverse Changing Climate

Rubio - who expressed deep skepticism about whether man-made activity has played a role in the Earth's changing climate - told Karl he doesn't believe there is action that could be taken right now that would have an impact on what's occurring with our climate.

"I do not believe that human activity is causing these dramatic changes to our climate the way these scientists are portraying it … and I do not believe that the laws that they propose we pass will do anything about it, except it will destroy our economy," he said.

Rubio said he didn't know of an era when the climate was stable.

"The fact is that these events that we're talking about are impacting us, because we built very expensive structures in Florida and other parts of the country near areas that are prone to hurricanes. We've had hurricanes in Florida forever. and the question is, what do we do about the fact that we have built expensive structures, real estate and population centers, near those vulnerable areas?" he asked. "I have no problem with taking mitigation activity."

EDITOR'S NOTE: We've added a portion of the full transcript that covers Jon Karl's conversation with Sen. Rubio below about climate change.

KARL: The White House came out with a big new report on climate change and listed Florida as being right, you know, saying that - that Florida is right at the center of this, that, in fact, Miami, Tampa are two of the cities that are most threatened by climate change. So putting aside your disagreement with what to do about it, do you agree with the science on this? I mean how big…

RUBIO: Well…

KARL: - a threat is climate change?

RUBIO: Yeah, I - I don't agree with the notion that some are putting out there, including scientists, that somehow, there are actions we can take today that would actually have an impact on what's happening in our climate. Our climate is always changing. And what they have chosen to do is take a handful of decades of research and - and say that this is now evidence of a longer-term trend that's directly and almost solely attributable to manmade activity…

KARL: You don't buy…

RUBIO: I do not agree with that.

KARL: - you don't buy the science on this? You don't think that human activity has caused the climate changes to somehow…

RUBIO: I think climate is always…

KARL: - or is the primary…

RUBIO: Well, I don't know of any era in world history where the climate has been stable. Climate is always evolving and natural disaster have always existed.

But I do believe that the fact is, that these events that we're talking about are impacting us, because we've built very expensive structures in Florida and other parts of the country near areas that are prone to hurricanes. We've had hurricanes in Florida forever.

And the - the question is, what do we do about the fact that we have built expensive structures, real estate and population centers, near those vulnerable areas?

I have no problem with taking mitigation activity. What I have a problem with is these changes to our law that somehow politicians say are going to change our weather. That's absurd.

RUBIO: - to say you are going to pass a bill that's going to change the weather is a lie and you're going to devastate our economy.

KARL: But - but let me get this straight. You do not think that human activity, the production of CO2, has caused warming to our planet?

RUBIO: I do not believe that human activity is causing these dramatic changes to our climate the way these scientists are portraying it. That's what I do not. And I do not believe that the laws that they propose we pass will do anything about it, except it will destroy our economy.