BOSTON — A box for energy. A box for foreign policy. A box for economics.

"Those boxes can't be separated anymore," said former U.S. Sen. Gary Hart in an interview with GlobalPost last week. "Everything fits together now."

Hart said the United States needs to link those boxes, or issues together to create a substantial platform for 21st century solutions to climate change.

"All of that relates to our economy. I defy anyone to say, 'Well, let's talk about the economy and forget about energy right now,' or 'Let's talk about energy and forget about our military.'

"Can't do it. "

Hart, long involved in the environment and energy debate, sees an opportunity for the United States to be a key player in the negotiations and take on a leadership position in December's Copenhagen Climate Change Summit. An early proponent of solar energy who served on the Senate's Environment and Public Works committee, Hart says that the U.S. needs to take a stand at Copenhagen.

"The world is waiting for the United States. We all need to be concerned about this and involved in it."

The most important result of Copenhagen is for the United States and China to negotiate a treaty upon which all parties can agree and that will regulate emissions, promote cleaner energy technologies in all countries, and provide assistance to countries that cannot afford to enact change themselves.

Multiple drafts of global warming and climate change treaties are circulating, but two are competing: one backed by the United States and the other championed by China.

The latter document — essentially an update to the 1997 Kyoto Protocol agreement, which the U.S. did not ratify — would require industrialized countries to severely decrease carbon emissions, while transitioning countries like China and India, two of the biggest polluters, would be held to milder standards.

"India, China, the developing nations and economies are going to take their cue from us," said Hart, who believes that the United States can resolve the debate.

"If we don't go and take a very strong position, they won't follow. It all depends on what position the United States takes and whether it provides a leadership position. We don't yet know what the Obama administration's policy is, in terms of what we're doing here, domestically, but also what proposals we will put on the table in Copenhagen."

In addition to the document that spawns from Copenhagen regarding carbon emissions, the former senator is concerned about global warming.

The objective "is to prevent the global climate from exceeding two more degrees," he explained. "About 1.4 degrees of that is not changeable, and we have to achieve the objective of reducing those emissions in 30 or 40 years to prevent a tipping point that can't be reversed."

He said he remains optimistic.

This report comes from a journalist in our Student Correspondent Corps, a GlobalPost project training the next generation of foreign correspondents.