David Jackson, USA TODAY 2:22 p.m. EDT August 23, 2015

President Obama(Photo: Carolyn Kaster, AP)

WASHINGTON — President Obama enjoyed a low-key vacation these past two weeks, but things are about to get very, very busy.

Obama, who returns to the White House Sunday night, faces a crowded five-week stretch that begins with events promoting his climate change policies and could end with another government shutdown.

In between: A high-profile meeting with Pope Francis, a tense visit from President Xi Jinping of China, an annual address to the United Nations General Assembly and tight congressional votes on the historic nuclear deal with Iran.

"It's going to be a busy early fall around here," White House spokesman Josh Earnest said.

A major theme for many of these events, Earnest said: Climate change.

The crowded month-and-a-half begins Monday when the president — who did not make an on-camera statement during his two-week vacation on Martha's Vineyard — travels to Las Vegas to discuss climate change policy at the National Clean Energy Summit.

Also on this week's presidential schedule: A Thursday trip to New Orleans to mark the 10th anniversary of Hurricane Katrina.

The challenges of global warming are also the reason that Obama plans to make an end-of-August trip to Alaska. He is scheduled to be the first president to visit the Alaskan Arctic region.

In the final days of August, Obama will also be planning a variety of major events in September. They include:

• The Iran nuclear agreement. The Republican-run Congress is considering an agreement in which the United States and its allies will reduce economic sanctions on Iran as it gives up the means to make nuclear weapons.

Republican criticssay the deal leaves too much room for Iran to cheat and develop nuclear weapons that could threaten Israel and the United States. The GOP has the numbers to approve a resolution of disapproval of the agreement, though Obama would veto it.

Obama, who says the agreement will avoid military confrontation by blocking Iran's paths to nuclear weapons, has been lobbying congressional Democrats. He is close to having enough support to sustain a veto.

• The visit of Pope Francis. Climate change will also be a major topic when Obama hosts Francis at the White House on Sept. 23, part of the pope's first trip to the United States.

Among other presidential-papal topics, the White House said: "Caring for the marginalized and the poor; advancing economic opportunity for all," as well as "protecting religious minorities and promoting religious freedom around the world; and welcoming and integrating immigrants and refugees into our communities."

• The visit of Chinese President Xi Jinping. The U.S. and Chinese leaders have much to discuss when Xi visits the White House in late September. (The precise date has not yet been announced.)

Things may get tense. The agenda is likely to include U.S. complaints about Chinese currency valuation, the nation's mutual economic troubles, allegations by each country of spying and cyber attacks on each other, a proposed free trade agreement involving Asian nations and territorial disputes between China and some of its Asian neighbors.

Climate change will also be a topic for the China meeting, the White House said.

• The United Nations General Assembly. This is another opportunity for Obama to discuss climate change as he makes his annual U.N. speech in late September. The president is likely to address an array of other global challenges, from economic recovery to the rise of the Islamic State.

A crowded month could end with another budget fight leading to a government shutdown.

If Congress cannot agree on a new spending plan by the time the fiscal year ends on Sept. 30, some government operations will be suspended.

These are the known events. Unexpected events could alter the president's schedule, making it even busier.

In his Saturday radio address, Obama also called on Congress to re-authorize the Export-Import Bank, saying that otherwise U.S. companies will be at a disadvantage to foreign competitors.

"Congress also hasn't passed a budget," Obama said. "And when they return from vacation, they'll only have a few weeks to do so, or shut down the government for the second time in two years."

Republicans said they have a budget, but Obama and the Democrats have blocked their efforts to scale back government.

"We've accomplished a lot over the past eight months, but we know we have a lot more work to do," said Sen. John Thune, R-S.D., in the Republican radio address. "And we have a president who is fighting us every step of the way."

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