BERLIN (AP) — Officials say U.N. talks on tackling climate change made limited progress over the past 10 days, but key issues still need to be resolved by year's end.

U.N. climate chief Patricia Espinosa noted Thursday that the meeting in Bonn, Germany, took place as Europe was gripped by a record-setting heat wave .

Australia, South Asia and the Middle East also experienced extreme temperatures this year in what scientists warn could be a sign of future conditions in a warming world.

Among the issues left unresolved are the rules by which countries can pay to cut greenhouse gas emissions elsewhere and count this toward their own targets.

Campaigners also lamented a further attempt by fossil fuel exporting countries to undermine a key scientific report on capping global warming at 1.5 degrees Celsius.