Perhaps it was the smiling French President Nicolas Sarkozy reaching out to grab Mr. Obama's arm, as if he'd just told the best joke the Frenchman had heard from an American since Jerry Lewis.
Or perhaps it was the beaming German Chancellor Frau Merkel giving an appreciative glance at the charismatic American president.
Or maybe it was British Prime Minister Gordon Brown calling the G-8's non-binding agreement "historic" and German Chancellor Angela Merkel pointing to "a clear step forward."
I couldn't help wondering whether the G-8 summit in the central Italian city of L'Aquila wasn't a well-orchestrated jab at the previous US administration and its resistance to 80 percent reductions. It all felt a little cloying.
At the end of the day, the US and other G-8 nations have pledged to reduce their greenhouse gas emissions by 80 percent or more by 2050, and agreed that global temperatures need to be prevented from rising more than 2 degrees Celsius or 3.6 degrees Fahrenheit.
Of course, not everyone was happy with the agreement. Both environmentalists and developing nations took issue.
While environmentalists welcome the shift in US policy, they are critical of the big industrial emitters' failure to agree on more immediate goals. Developing nations feel that complying with major reductions will hamper their economic growth and keep their people in poverty.
According to sources close to the situation, representatives of developing nations, such as China, India, and Brazil still feel those who have benefited from 100-plus years of unbridled development should do more.
In other words, the burden of emissions reduction should be on those who created the problem, not on those who are struggling to catch up.
There is no question that China and India will be a major force in the upcoming negotiations. They have much at stake: both are still heavily reliant on coal to fuel their economies, but both also seem to be serious about investing in alternative energy development.
China and India seem to be serious about developing a low-carbon economy -- or at least seizing a large share of the market.
Last month, Zhang Xiaoqiang the vice-chairman of China's National Development and Reform Commission, said that China wants to produce one-fifth of its energy needs from renewable sources by 2020.
According to Lou Schwartz, of China Strategies LLC, the Chinese will spend over 3 trillion Yuan (roughly US$462 billion) on alternative energy development in the next decade. This includes 100,000 MW of installed wind power capacity by 2020.
Meanwhile, in a visit to the Solar Energy Centre in Gurgaon last month, Indian Minister for New and Renewable Energy, Dr. Farooq Abdullah, pledged that "new and renewable energy will increasingly play a larger role in meeting the development aspirations of a growing economy like India."
The US and other G-8 countries need to take notice, listen to the concerns of developing nations and do more to enable those countries leapfrog dirty technologies, while doing more at home to facilitate their own swift transition.