The US Special Envoy for Climate John Kerry called on the European Union and the world's largest emitters to drastically reduce emissions within the next 10 years.
In an interview with DW's Michaela Küfner, Kerry said he hoped to rally countries ahead of the 2021 United Nations Climate Change Conference (COP26) in Glasgow in November.
"It's critical that the 20 biggest emitters in the world, of which we are one, and the EU [as a whole] ... and India and China and others, we have to step up. All of us have to lead here by example," he told DW.
"And that means we need to be achieving significant reduction goals, not just by 2050, but over the next 10 years. If we 20 nations that are the largest economies of the world don't mitigate — meaning, reduce our emissions during 2020 to 2030 — then we would be responsible for denying the rest of the world the ability to hold the temperature well below 2 degrees or at 1.5."
"That's what we're trying to do now, hopefully achieve through climate diplomacy over the course of the next months before we go to Glasgow. So in Glasgow, the less developed world will be able to know that we've got the $100 billion (€82 billion) we pulled together that has been promised and that we are doing our part to keep 1.5 degrees alive."
Kerry was referring to the commitment reached in Copenhagen in 2009 to create a $100 billion annual climate fund for poorer nations by 2020. The funds remain shy of that goal, partly due to the presidency of Donald Trump.
The US is hoping to work with other countries in the coming months to meet the pledge.
Glasgow is 'world's most important moment'
Kerry said COP26 would be a critical juncture for the future of the world and that it was critical to act responsibly.
"This is the world's most important moment with respect to multilateralism and a global effort to solve a major international challenge," he told DW. "If we don't get it right in Glasgow, then we will be leaving certain parts of the world in chaos and disorder and in great pain over the ensuing years."
"The less developed world has not caused this problem, and they are patiently waiting for the developed world to step up and exercise their responsibility. And young people are asking adults to behave like adults and get the job done."
What is Kerry doing in Berlin?
Kerry was Barack Obama's secretary of state during his second term and helped bring chief polluter China into the Paris agreement, which limits global warming to well below 2 degrees.
The 77-year-old has been appointed as Joe Biden's climate envoy and has been in a diplomatic spree ahead of COP26.
He traveled to Berlin on Monday and was due to stay until Wednesday.
Kerry has met with German political leaders from most parties, urging cooperation on climate change.
His schedule included meetings with the three main candidates to become chancellor of Germany in September's elections — the CDU's Armin Laschet, Olaf Scholz of the Social Democrats and Annalena Baerbock of the Greens.
However, he ducked questions about the upcoming vote or the prospect of a government led by Germany's Greens.
"Well it's up to the people of Germany to decide, you know ... We certainly support the policy of addressing the climate crisis. And obviously the Greens are very seized by and engaged in that particular issue.
But "unlike Russia, we're not going to involve ourselves in other people's elections," Kerry said.
Ahead of his meeting with Kerry, German Foreign Minister Heiko Maas stressed the importance trans-Atlantic solidarity in fighting climate change.
"With the new US administration, this cooperation will be revitalized," his ministry said in a statement.
What are the US and German climate change plans?
Biden's administration recently unveiled new climate targets, pledging to at least halve greenhouse gas emissions by 2030 compared to 2005.
The German cabinet too unveiled new climate targets, including greenhouse gas neutrality by 2045. They also pledge to cut emissions by 65% by 2030 and by 88% by 2040 compared to 1990 levels.