President Trump said at his inauguration on Monday that he would sign a barrage of executive orders to grant his administration new powers to promote fossil fuels and to withdraw support for renewable energy, signaling that the United States government would no longer fight climate change.

Mr. Trump also intends to withdraw the United States from the Paris Agreement on global warming, for a second time. He said that vast areas of public land and federal waters, including fragile wilderness in Alaska, would be thrown open for oil and mineral extraction. And he said he would repeal regulations aimed at promoting electric vehicles and stop new offshore wind farms from being built in federal waters.

Mr. Trump also said he planned to declare a national energy emergency. He would be the first president to do so, despite the fact that the United States is currently producing more oil and natural gas than any other country. That declaration could unlock authority to suspend some environmental regulations and speed permits for oil and gas drilling, as well as authority to keep coal-fired power plants running.

“We will drill, baby, drill,” Mr. Trump said in the Capitol after taking the oath of office.

Mr. Trump’s pivot to fossil fuels comes after the hottest year in recorded history and as scientists say the world is running out of time to keep global warming at relatively low levels. Last year, emissions from burning coal, oil and gas helped push average global temperatures past 1.5 degrees Celsius, or 2.7 degrees Fahrenheit, above preindustrial levels. Scientists have said that every fraction of a degree of warming above that level brings greater risks from deadly heat waves, wildfires, drought, storms and species extinction.

Most of Mr. Trump’s energy policies can’t be achieved with the mere stroke of a pen because some would require action by federal agencies or Congress and others could face legal challenges. He also could not, by fiat, rename the Gulf of Mexico to the Gulf of America, or Denali in Alaska, the highest mountain peak in North America, to Mount McKinley. Mr. Trump promised to do both.

But taken together, the declarations underscore how Mr. Trump views the world: America has been weakened by efforts to fight climate change, oil and gas are symbols of strength and power, and plentiful fossil fuels will ensure that the U.S. is able to dominate allies and rivals alike.