The 2009 TIME 100

Last year, Connie Hedegaard invited Environment Ministers to strap on their boot spikes and join her for a hike up the Perito Moreno Glacier in Argentina. The goal of the trip: to see firsthand the effects of climate change. Now Connie and her international colleagues are gearing up for another adventure — the U.N. Framework Convention on Climate Change in Copenhagen in December.

As host of this high-stakes meeting, Connie, 48 — the Climate and Energy Minister of Denmark — is under enormous pressure to deliver results. There is no longer any doubt that climate change is happening — and it may be happening a lot faster than we thought.

Connie understands this. Climate change is a uniquely global problem and requires a uniquely global response. The challenge in the run-up to Copenhagen is to find a way for an entire world to unite around a plan that is both fair and effective. I have no doubt that Connie Hedegaard is up to the task. But strap on your boot spikes — it is going to be a tough climb.

Claussen is president of the Pew Center on Global Climate Change