U.S. Sen. Marco Rubio took a high-profile political trip to New Hampshire last week and then declared on Sunday he is ready to be president. There is plenty of evidence to the contrary, such as the Florida Republican's refusal to acknowledge that humans are contributing to climate change and that government has a responsibility to address it. Responding to climate change is a key issue for Florida and the nation, and the country cannot afford to elect a president who ignores science and denies reality.

The latest federal report, the Third National Climate Assessment, reaffirmed last week what the overwhelming consensus in the scientific community has been for years: Climate change is real, the impact is being felt now and the primary cause is "human activities, particularly the burning of fossil fuels.'' Yet Rubio stuck to his discredited talking points Sunday after his well-received swing through the first-primary state.

"I do not believe that human activity is causing these dramatic changes to our climate the way these scientists are portraying it,'' he said on ABC's This Week, adding, "Our climate is always changing. They've chosen to take a handful of decades of research and say that it is now evidence of a longer-term trend that's directly and almost solely attributable to man-made activity.''

That is a politician in denial who is not up to responsibly tackling a complicated, serious challenge facing the nation and the world. With nothing credible to bolster his position, Rubio rejects the latest assessment by dozens of scientists working over five years — and the stacks of earlier reports and studies that pointed toward the same conclusion. This is not the sophisticated, critical thinking voters expect from the nation's leader. The senator trails evolving public opinion among voters who have more respect for established science and what they see with their own eyes than the senator does.

Rubio doesn't just discount the scientists' conclusion that humans are causing climate changes that are triggering rising temperatures, higher sea levels and decreasing snow and ice cover in the Arctic. He also doesn't want government to do anything about it.

"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 on our climate,'' Rubio said on ABC. "I do not believe that the laws that they propose we pass will do anything about it, except it will destroy our economy.''

What will destroy the economy, and create more instability around the world as undeveloped nations experience severe droughts and food shortages, is if government fails to act on climate change. Rubio should drive around his home county, where some Miami-Dade communities are experiencing regular street flooding caused by higher tides. He should talk to local officials in South Florida and Tampa Bay, who are concerned about climate change and how it will affect coastal development, tourism along eroding beaches and flooding in low-lying neighborhoods. He should call the Defense Department, which is studying how national security is threatened by unrest elsewhere that can be traced to the impact of climate change.

Rubio apologists parse his climate change comments. They note he qualifies his doubts about humans causing climate change by adding "the way these scientists portray it.'' When pressed, the senator's office falls back on this easy deflection: "He's not a meteorologist.'' But make no mistake. Rubio is signaling to the climate change deniers and the tea party crowd that helped elect him to the Senate in 2010 that he is on their side.

It's bad enough that Rubio and some of his Republican colleagues in the Senate reject established science and ignore reality. It would be even worse to elect a president who is in denial about the causes of climate change and the responsibility of elected leaders to do something about it.