By Richard Black
Environment correspondent, BBC News website, Poznan
How the US' per-capita emissions stack up against Burkina Faso's
UN secretary-general Ban Ki-moon has called for "new global solidarity" on climate change, as ministers began two days of talks on the issue.
Ministers from 189 nations aim to finalise agreements drawn up here at the annual UN climate conference.
As they talk, EU heads of state are meeting in Brussels to agree energy and climate reforms, including promises to reduce greenhouse gas emissions.
Developing country leaders have called on the EU to adopt strong measures.
Developing nations and environmental groups have repeatedly accused rich countries of not showing enough leadership at the conference here, which marks the half-way point in a two-year process initiated at the UN talks in Bali last year.
Over the last year, governments have submitted ideas on what they would like to see in a new global pact, which is supposed to be finalised by next year's meeting in Copenhagen.
Mr Ban said that economic concerns must not prevent developed countries from investing in elements of a "green economy", such as renewable energy, or from helping poorer nations to put their economic development onto a sustainable footing.
"We need a deal on climate change that will unleash a wave of investment in a green future," he told delegates at the opening session.
Referencing leading figures and events in Polish history, he called for a "new Copernican revolution" in industrial paradigms, and said the world "needs a global solidarity on climate change - the defining challenge of our era".
Also speaking at the opening plenary session, President Bharrat Jagdeo of Guyana said the developed world's response to the banking crisis showed what could be done.
"Some may baulk at the scale of the financial resources required," he said.
"But if the will is there, the money will be found, as demonstrated when developed nations found seven trillion dollars to tackle the financial crisis."
If banks are too big to fail, he added, so is the climate, urging the international community to commit to cutting greenhouse gas emissions by 80% by 2050 - further than 50%, which is the target principally under discussion here.
Apisai Ielemia, Prime Minister of Tuvalu, said the West - and the larger developing economies - must make stringent cuts to avoid major damage to island states such as his.
"We cannot sink while others rise," he said.
Some EU countries, including Poland and Italy, are concerned that the climate and energy package being negotiated in Brussels will cost too much, and are asking for concessions.
Protesters want action as soon as possible
The bloc is set to pledge emissions cuts of 20% from 1990 levels by 2020, or by 30% if there is a global deal.
Many observers here feel that the lack of agreement on the package has reduced the impetus of the UN talks here, and that a weakened deal in Brussels would send "the wrong signal".
In addition, the EU has not yet published proposals on giving financial assistance for developing countries that could help them restrain the growth in their carbon emissions, which will be a vital component of a future global treaty.
Another factor curbing progress is the fact that the US delegation represents the outgoing administration of George Bush rather than the incoming one of Barack Obama.
All this may mean, some observers say, that the timescale is too tight to reach a Copenhagen deal that includes firm targets on reducing emissions.
Many of the documents that officials from the 189 countries have been discussing for the last two weeks have been agreed with little demur.
However, there are still serious wrangles over some issues which could not be resolved before the ministerial segment.
One concerns the UN Adaptation Fund, a pot of money designed to help developing countries protect their societies and economies against potential impacts of climate change.
Current proposals see the World Bank as a major player in managing the money.
Developing countries are unhappy with this, and want a separate body set up that would, as they see it, be more responsive to their needs - the sting in the tail being that this wrangle could delay the first payments from the fund.
The meeting is scheduled to end on Friday evening here, but some delegates believe talks may run through the night into Saturday, as has been a feature of many this conference's predecessors.