Climate change contributed to the wave of German immigration to the US that included Donald Trump’s grandfather.

In the 19th century, more than five million Germans migrated to North America.

One such German was Friedrich Trump, the grandfather of the current US President, who arrived in New York in 1885 as an unskilled 16-year-old who couldn’t speak English.

Protestors rally at JFK Airport against Muslim immigration ban Show all 20 1 /20 Protestors rally at JFK Airport against Muslim immigration ban Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-1 Protestors rally during a demonstration against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-2 Protestors rally during a protest against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump singed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. 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Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-7 NEW YORK, NY - JANUARY 28: Protestors rally during a demonstration against the new immigration ban issued by President Donald Trump at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-8 Protestors rally during a demonstration against the new immigration ban issued by President Donald Trump at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. 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(Photo by Stephanie Keith/Getty Images) Getty Images Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-11 NEW YORK, NY - JANUARY 28: Protestors rally during a demonstration against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-12 Protestors rally during a demonstration against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump signed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. 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Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-17 NEW YORK, NY - JANUARY 28: Protestors rally during a protest against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump singed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. Stephanie Keith/Getty Protestors rally at JFK Airport against Muslim immigration ban jfk-protest-muslim-ban-18 Protestors rally during a protest against the Muslim immigration ban at John F. Kennedy International Airport on January 28, 2017 in New York City. President Trump singed the controversial executive order that halted refugees and residents from predominantly Muslim countries from entering the United States. 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British authorities arrested 21 people and halted a anallegedly terrorist plot to use liquid explosives concealed in carry-on luggage to blow up airliners traveling between Britain and the U.S. Homeland Security chief Michael Chertoff said that the plot appeared to be directed at U.S. carriers flying out of Heathrow. such as United Airlines, American Airlines, Continental Airlines. Stephen Chernin/Getty

Germans like Friedrich Trump came to the US in part because they were looking for “peace and freedom”, said Professor Rüdiger Glaser, a physical geographer at the University of Freiburg, Germany.

But according to a new study led by Prof Glaser, changes in Europe’s climate were also responsible for up to 30 per cent of emigration from south-west Germany to North America during this period.

Climatic instability was triggered by the tail end of a period known as the Little Ice Age, and exacerbated by the massive eruption of Mount Tambora, a volcano in Indonesia.

The volcanic eruption expelled so much sulphur into the atmosphere that the sun was obscured for more than two years.

During this time, droughts, floods and cold temperatures culminating in the so-called Year Without a Summer had dire consequences for many Europeans.

“There is a chain of events which goes climate extremes, drop in harvest yields, rising prices and then the people are migrating,” said Prof Glaser, lead author of the Climate of the Past study.

Focusing on the Baden-Württemberg region of south-west Germany, Professor Glaser and his collaborators studied migration statistics and population data, and compared them with weather data, harvest figures and cereal prices.

“Trump, he comes from south-west Germany – the Palatinate, the neighbouring region to Baden-Württemberg,” said Professor Glaser.

They concluded that besides social and political changes such as the Napoleonic wars, climate made a significant contribution to German emigration.

According to Prof Glaser, it’s important that world leaders like Mr Trump are aware of past waves of migration in the context of climate change.

“It’s really touching today’s main discussions on the global scale,” said Prof Glaser.

Immigration due to climate change is a pertinent issue, with Fiji recently declaring that more than 40 villages are being relocated to higher ground to escape rising sea levels.

Europeans and North Americans, too, should bear in mind their own history of climate-induced immigration, said Prof Glaser.

“The out-migration movement to North America is still the most significant migration movement ever,” he added.