The talks now in their second week are largely technical in nature. But the Trump administration's threat to pull the U.S. out of the agreement and extreme weather events in many parts of the world have created pressure for other governments at the meeting to strongly affirm their support for the 2015 Paris accord.
Much of the limelight Wednesday is expected to fall on Chancellor Angela Merkel of Germany, which is co-hosting the U.N. talks in Bonn with Fiji. Environmental campaigners want Germany to show its commitment to curbing global warming by announcing a deadline for phasing out the use of coal, a major greenhouse gas.
President Hilda Heine of the Marshall Islands, whose country risks being swallowed by the Pacific Ocean if global warming causes sea levels to keep rising, said a declaration that Germany will end its use of coal "would be a signal of hope for my country and for every vulnerable country around the world."
Merkel will be joined by U.N. Secretary-General Antonio Guterres and French President Emmanuel Macron, who has come out strongly in favor of efforts to fight climate change since taking office earlier this year.
Still, with U.S. President Donald Trump saying he wants to withdraw from the Paris treaty, scientists warn it will be difficult to achieve the central goal of keeping global warming well below 2 degrees Celsius (3.6 degree Fahrenheit) by the end of the century.
A group of U.S. states, cities and businesses that back the Paris accord have become the go-to contacts for many negotiators in Bonn who remain eager to work with the United States.
Washington's official delegation has been largely invisible at the talks, save for a U.S.-sponsored event promoting fossil fuels and nuclear energy late Monday that drew vocal protests from environmental campaigners.
The talks have also seen dozens of announcements from businesses and governments that pledged to reduce emissions or to commit large sums of money to helping poor countries tackle the effects of climate change.
The meeting, which is scheduled to end Friday, is aimed at producing draft rules for implementing the Paris accord. The rules would need to be finalized by the time of next year's global climate talks in Poland.
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