In a two-hour discussion with Elon Musk, on the billionaire’s platform X, Donald Trump made a number of questionable and false claims – which went largely unchallenged.

The Republican presidential candidate returned to some familiar campaign themes, such as illegal immigration and rising prices, but he also talked about climate change.

BBC Verify has been checking some of his claims.

CLAIM: “The biggest threat is not global warming, where the ocean is going to rise one eighth of an inch over the next 400 years.”

VERDICT: According to climate projections, Trump is vastly underestimating the rise in sea levels.

In the decade 2014-2023, global average sea levels rose by an average of nearly 4.8mm per year (0.19in), according to the World Meteorological Organization.

That increase is already greater than the one eighth of an inch (0.13in) that Mr Trump predicts will happen over the next 400 years.

The magnitude of future rises is difficult to predict, because it is uncertain how quickly ice-sheets will melt, and future warming will depend on greenhouse gas emissions from human activities.

The UN’s Intergovernmental Panel on Climate Change (IPCC) has estimated a likely range of 0.28 to 1.01m of global sea-level rise by 2100 – although higher rises can’t be ruled out.

A sea-level rise of one metre would put hundreds of millions of people at risk of more regular coastal flooding, as well as submerging parts of low-lying countries such as the Maldives.

CLAIM: “I think 20 million people have come across the border… I think millions are coming every month.”

VERDICT: It isn’t possible to know exactly how many illegal immigrants have entered the US across its southern border during President Biden’s time in office. Official data suggests it did hit record levels but not the kinds of numbers Mr Trump claims.

Since January 2021, the US Customs and Border Protection agency says there have been 10.1m encounters of illegal migrants by enforcement officers in the US, with more than 8m of those coming over the southern border.

These figures don’t necessarily mean all these people successfully entered the US – some may have been sent back and the same person could be “encountered” trying to cross the border multiple times.

The official figures do represent a significant increase on the four years under Trump, and is also the highest figure recorded under any US administration.

The data doesn’t show “millions” coming every month either. US Border Patrol agents apprehended around 57,000 migrants along the southern border in July – the lowest recorded since September 2020.

The numbers are down significantly from the peak under Mr Biden in December 2023, when around 250,000 migrants were caught crossing the border.

CLAIM: “I think we have the worst inflation we’ve had in 100 years… bacon costing four or five times more than it did a few years ago”.

VERDICT: This is false. Inflation peaked at 9.1% under President Biden – the highest in 41 years, not 100. The price of bacon is up 17% since Trump left office, not four or five times.

Inflation rose significantly during the first two years of the Biden administration, reaching the highest level since 1981.

This was comparable with many other Western countries, which experienced high inflation rates in 2021 and 2022, as global supply chain issues as a consequence of Covid and the war in Ukraine contributed to rising prices.

Some economists say Mr Biden’s $1.9tn (£1.5tn) spending plan in 2021 was a factor as well.

Since mid 2022, US inflation has fallen, with the latest monthly figure at 3% as of June.

In terms of bacon – the average price for a pound of sliced bacon was $5.83 in January 2021 when Trump left office, according to the US Bureau of Labor Statistics. It now costs $6.83.

CLAIM: “I built hundreds of miles of wall” to protect the southern border.

VERDICT: The length of border wall built during Trump’s presidency depends on what you are measuring, but if you include new sections as well as parts that have been replaced or reinforced, he built more than 450 miles.

A report by US Customs and Border Protection puts the total at 458 miles. However, only 85 miles of entirely new sections of wall were built under Trump.

The rest has been either replacing or reinforcing existing barriers.

President Biden suspended construction when he came into office, but last year his administration allowed the building of a section of wall in an effort to stop rising levels of immigration.

The section approved by Mr Biden is for 20 miles of barriers along the border in southern Texas.

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