University of Washington Professor Nives Dolsak has studied climate change for 20 years from the perspective of a political scientist. On Thursday, she responded to some of President Trump's reasons for pulling out of the Paris Climate Agreement.

Q: The U.S. has pledged up to $3 billion dollars to help developing countries cut green gas emissions. President Trump says the US is paying more than its share. "The Paris Accord is very unfair at the highest level to the United States."

A: Historically, Nives says, the US has been one of the biggest polluters.

"If you look at the data since 1850, which is when the large-scale greenhouse gasses started, the United States accounts for about a quarter of the emissions, the EU (European Union), for about another quarter, China about 11 percent, India about 4 percent."

Q: What about American jobs? President Trump says, "Compliance with the terms of the Paris accord and the onerous energy restrictions it has placed on the United States could cost America as much as 2.7 million lost jobs by 2025."

A: "Look at the letters that a number of companies have sent to the White House asking the White House not to pull out of the agreement."

16 companies - including Apple, BP, DuPont, Microsoft, Shell and Walmart – have urged the president to continue participating in the Paris agreement. According to their letter: "We believe that as other countries invest in advanced technologies and move forward with the Paris Agreement, the United States can best exercise global leadership and advance U.S. interests by remaining a full partner in this vital global effort.

Q: The agreement isn't a treaty. "The United States will cease all implementation of the nonbinding Paris accord and the draconian financial and economic burdens the agreement imposes on our country."

A: Nives say the US will lose its voice and international leadership on the environment. "What matters is that we are no longer at the negotiating table and that hurts us more than it hurts anybody else."

Q: The president isn't closing the door on a climate deal. "I'm willing to immediately work with Democratic leaders to either negotiate our way back into Paris under the terms that are fair to the United States and its workers or to negotiate a new deal that protects our country and its tax payers," Mr. Trump said.

A: But Nives notes it took decades to get China and India to the climate negotiating table.

"I have been studying common world resources and climate change for about 18, 20 years now as a political scientist," Nives says. "In my opinion it is one of the most challenging political issues that we have to resolve at the global level and as well at the national level in the United States."