Delegates from almost 200 nations will begin talks in the Polish capital, Warsaw, on Monday to prepare for a global summit on a UN climate pact.
The search for new targets on emissions cuts promises to be a hotly debated issue with many developed nations eager to set a more cautious tone, but some environmental campaigners say tough action is still needed.
The biggest greenhouse gas emitters China and the United States have pledged to curb carbon, but on a modest scale.
China has promised to cut emissions per unit of economic output by between 40 and 45 percent on 2005 levels by 2020. As a reduction relative to gross domestic product (GDP), that will slow growth in emissions but not cut them.
The United States has said it will reduce carbon by 17 percent by 2020 compared with 2005, which equates to a fall of 3.5 percent below 1990 levels.
In Europe, recession and green energy use mean the EU has already nearly met its 2020 target of a 20 percent cut versus 1990 in greenhouse gas emissions, which include carbon and methane.
Goals for 2020 agreed by EU leaders in 2007 became an international benchmark for climate ambition.
Scientific opinion has since become more convinced mankind is to blame for changes to the climate
The EU is still the main group among developed nations urging governments to declare their emissions goals, but critics fear the political focus has shifted to the economic crisis.