A longtime negotiator for Germany on environmental issues, Karsten Sach holds a doctorate in law. He is a veteran of the climate negotiations, having led the German delegation since 1999.

Sach, who is cool and calm, has shown frustration in the past at the glacial pace of negotiations. In an interview with Deutsche Welle, he complained how boring the negotiations get when people keep on repeating the same things for days. “I hate debating just for the sake of debating. It gets on my nerves when people repeat things for the 10th time because they think the others aren’t listening  properly,” he said.

With Germany and France emerging as close allies in the push for a legally binding agreement, Sach will play a key role in ensuring that 2015 has a better outcome than 2009. It was that year when a frustrated Angela Merkel threw up her arms in a closed-door meeting, exasperated at China’s politicking and its stubborn opposition to a strong deal. Sach will be under pressure to find a path to a more positive result in Paris.