German Chancellor Angela Merkel's scientist-husband will take leaders' spouses at a G20 summit, including Melania Trump, to a climate research centre amid a bitter row over global warming.

Joachim Sauer, who usually shuns publicity, will  take the visiting dignitaries sightseeing through Hamburg on a river cruise and to the spectacular new Elbphilharmonie concert house.

But the quantum chemist has also insisted they stop off at the German Climate Computing Centre -- an itinerary point sure to put the spotlight on the US First Lady after President Donald Trump in June pulled out of the 2015 Paris climate accord.

The leaders' wives -- Sauer is the only husband as British Prime Minister Theresa May's spouse won't be coming to Hamburg -- will also take in views of Germany's "Gateway to the World" city on a cruise tour of the country's biggest port, in whose harbour-front bars the Beatles started their rise to fame.

The G20 spouses' tour also includes Hamburg's neo-Renaissance town hall, an imposing building dating from the late 1800s, which boasts almost as many rooms as Britain's Buckingham Palace.

On Friday evening, the spouses will be treated to Beethoven's "Ode to Joy", the EU's anthem, at Hamburg's new Elbphilharmonie, whose glass structure is meant to evoke frozen waves, and which offers sweeping views of Germany's second largest city.