The final presidential debate focused on America's involvement in the oil-rich Middle East and on future threats to the nation, though neither candidate discussed the related risks of climate change.

The contest between President Obama and Mitt Romney capped a string of four debates in which they and their running mates failed to mention the topic of rising temperatures. It was the first time that has happened since the problem was identified in the 1980s, according to Brad Johnson, campaign manager of Climate Silence.

"Climate change threatens us all: the candidates' silence threatens to seal our fate," he said in a statement after the debate.

The candidates clashed last night on related issues of energy and national security, which the Pentagon has warned could increasingly be affected by climate change as drought and natural disasters pressure populations to move. The military's humanitarian missions could escalate along with other responsibilities related to warming, like navigating an increasingly accessible Arctic Ocean.

Before the debate, some analysts said the prospect of fluctuating oil markets associated with political volatility in the Middle East could invite a discussion about the candidates' plans for energy independence. That didn't happen.

Obama did not expand on the ideas he presented in a previous debate last week about reducing gasoline use through efficiency measures in the transportation sector. And Romney did not address his support of cleaner fuels like ethanol and biofuels.

The candidates also avoided a discussion about international efforts to address climate change, a diplomatic priority for many U.S. allies.

"Europe remains fixated on the issue and might reconsider carbon tariffs on the United States down the road," Michael Levi, a senior fellow at the Council on Foreign Relations, wrote on his blog before the debate. "Scores of countries in Asia and Africa care deeply about what climate change will do to their safety and prosperity -- and the United States is battling with China for their allegiance."

Other climate topics related to China also did not come up, like its breakaway production of solar panels and its massive investments in clean energy technology.

"One of the messages I think you would see the president give ... is China is charging forward both on its own regulatory measures to limit emissions, but also obviously in its strong commitment to being a leader in clean energy production and deployment," Roger Ballentine, the former chairman of the White House Climate Change Task Force under President Clinton, said before the debate. "The president will have a chance to say that's a leadership position which we in the United States should have -- have traditionally had."

A long bipartisan tradition ends

The absence of climate change has frustrated a range of people, from religious activists and environmentalists to college students who want to see a deeper discussion about future energy sources.

"I'm really passionate about this subject, because it does affect my generation and generations to come," said Duresny Nemorin, a student at Florida Agricultural and Mechanical University who led a climate rally before the debate in Boca Raton, Fla. "There are other ways to power our houses and power our cars. Why can't we investigate into different ideas? Why can't we be creative as a nation?"

This is the first time since 1988 that climate hasn't been mentioned in the presidential debate cycle, Johnson of Climate Silence said in a post that provides partial transcripts to the contests. Back then, Republican vice presidential candidate Dan Quayle said, "the greenhouse effect is an important environmental issue."

In 2008, Obama and Sen. John McCain (R-Ariz.) discussed efforts to reduce emissions in three debates, including in one presided over by last night's moderator, Bob Schieffer. Their running mates also talked about it, with Sarah Palin (R-Alaska) touching on the dangers faced by her home state.

This year's omissions make the prospects cloudy for climate action in the next four years, whether the nation is led by Obama or Romney.

Both believe that warming is happening, though Obama emphasizes more strongly that humans are a key contributor to the problem. Now, without detailed explanations of how, or if, their administrations would tackle the problem, some observers are concerned that climate change is tumbling down the priority list of the next president.

"We know what Obama has done to date, which has been positive and good, but we don't hear anything about what the next four years will hold in terms of carbon reduction," said Larry Schweiger, president of the National Wildlife Federation.

Reprinted from Climatewire with permission from Environment & Energy Publishing, LLC. www.eenews.net, 202-628-6500