Dismayed by the German government's failure to meet climate protection targets, dairy farmer Heiner Luetke Schwienhorst has filed a lawsuit against Berlin to force it into action.

"Some describe this as a fight between David and Goliath. To me, that's besides the point," said Schwienhorst, who suffered his poorest harvest in three decades after a record drought.

"The attitude of political representatives, the way they trivialise climate targets by giving up what they have set, is something that we need to bring to political accountability. That is important," he told AFP.

A dairy farmer near Hamburg and a livestock farmer on the North Sea island of Pellworm have joined the first such lawsuit to seek "climate protection, not monetary compensation".

Berlin had pledged to take action to slash greenhouse gas emissions in Germany by 40 percent by 2020 compared to 1990 levels.

But in its latest annual climate protection report published in June, the government admitted that it was now expecting to achieve 32 percent in reductions compared to 1990.

The shortfall of 8 percentage points is equivalent to about 100 million tonnes of carbon dioxide.

"It was clear in the climate protection report that the government is not planning to take further measures in order to reach the target. Instead, it has simply given up," said Anike Peters of Greenpeace.

"We're saying we're not going to accept this. Because it's not about a lack of technical possibilities to reach the target, rather it's about a lack of political will.