Fast-growing economies like China, India and Brazil must cut their large greenhouse gas emissions, Merkel has said.
"Worldwide CO2 emissions this year were higher than ever," she said in parliament.
"We are in an extremely difficult situation where the Kyoto Protocol expires, we have not got far and an extension of the protocol will unfortunately not happen in Durban."
Negotiators from almost 200 countries meet this week in South Africa for a U.N. climate summit, where only modest steps are expected towards cutting greenhouse gas emissions despite warnings from scientists that extreme weather will likely increase as the planet warms.
The Kyoto Protocol, the U.N. plan obliging some 40 industrialised nations to cut emissions, expires next year.
Rich nations are reluctant to target major emission cuts beyond 2012 without commitments from big developing economies to curb theirs.
The latter want to see deeper cuts from wealthy nations.
The World Meteorological Organisation said this week the three main greenhouse gases blamed for global warming reached record levels in 2010.
Major developing economies such as China, India and Brazil were not ready to enter into binding international agreements on reducing emissions, Merkel said.
"That means that we are unfortunately becoming a world where the increasingly important economies are not appropriately contributing to a sustainable environment," she said.