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KNOW IT ALL: Tuesday's Top 7 Stories at NBC News

From the U.S. and Arab airstrikes in Syria against ISIS to world leaders gathering about climate change, see the stories we're following.

Good morning, and happy Tuesday. Here are some of the stories we're following today:

1. U.S. launches airstrikes against ISIS in Syria

A military offensive early Tuesday carried out by the United States and five Arab allies is the first significant strike against ISIS in Syria. “I can confirm that U.S. military and partner nation forces are undertaking military action against (ISIS) terrorists in Syria using a mix of fighter, bomber and Tomahawk Land Attack Missiles,” Rear Adm. John Kirby, the Pentagon press secretary, said in a statement. The operation is meant to take out not only ISIS targets but seasoned al Qaeda veterans as well. The U.S. acted alone in targeting the “Khorasan group,” U.S. Central Command said. The Syrian foreign ministry, meanwhile, said that Washington informed Damascus’ envoy to the United Nations about launching the airstrikes in northern Syria. Read more in NEWS.

2. World leaders gather on climate change

President Barack Obama will address world leaders at the U.N. Climate Summit in New York City on Tuesday, two days after a global march to bring attention to demand action on climate change. Activists are hoping the U.N. can set achievable goals, although no global carbon agreement will be signed at the summit. That does not mean a handful of smaller countries, such as Denmark, won't set ambitious carbon reduction goals to try to influence the major players at the negotiating table. Read more in ENVIRONMENT.

3. Who is the White House fence jumper?

Omar J. Gonzalez took an arsenal with him when he went to the White House on Friday and managed to jump the fence and race past security. The 42-year-old was carrying a knife and had two hatchets, a machete and 800 rounds of ammunition in his car. While the president was away and Gonzalez did not harm anyone, his ability to breach the White House property was a wake-up call. His family and friends say the Puerto Rican-born former Army soldier needs psychological help. “Looking back, I wish there was something I could do to help him. He’s not a bad guy. He needs to get treatment,” his ex-wife told NBC affiliate WHTR. Read more in NEWS.

4. Suspects in Israeli teens’ fatal abduction killed

Two Palestinian suspects were killed in the West Bank in a shootout with Israeli forces, officials said Tuesday. The men are accused of taking part in the kidnapping and killing of three Israeli teens in June, which touched off a massive search and ultimately renewed weeks-long fighting between Hamas and Israel in the Gaza Strip. Hamas had claimed responsibility for the abduction. Read more in NEWS.

5. Missing Afghan soldiers captured by Canada

Were they trying to make a run for the border? The three Afghan National Army officers who disappeared from training in Massachusetts over the weekend were apprehended trying to cross into Canada at Niagara Falls, officials said Monday. The Massachusetts State Police added that the men were being interviewed by federal authorities, but there was “no information that suggests the three men committed any crimes.” It’s possible the men were trying to cross into Canada to take advantage of the country’s more liberal asylum policies. Read more in NEWS.

6. Ebola infections predicated to rise dramatically

The virus ravaging West Africa could reach 20,000 cases by November, with 70 percent expected to die, the World Health Organization said. This projection includes nearly 10,000 people in Liberia alone. “The true numbers of cases and deaths are certainly higher,” WHO wrote. But experts say the number of infected doesn’t have to climb so dramatically if the world acts quickly. The U.S. is sending troops and medical personnel to help officials train workers in Africa and build adequate medical facilities. Read more in HEALTH.

7. Apartment searched in case of missing student

Charlottesville, Virginia, police combed the apartment Monday of a “person of interest” whom they want to interview in the disappearance of 18-year-old Hannah Graham. Jesse Matthew has two arrest warrants for reckless driving shortly after Graham, a student at the University of Virginia, disappeared more than a week ago. Police say Matthew has been uncooperative and they can't find him. They believe that he was the last person to have seen Graham before she vanished. Read more in NEWS.

… What’s trending today?

Get your cute fix by checking out these two adorable baby cheetahs being raised by the staff of the San Diego Zoo.