A claim by Britain’s leading climate science sceptic, Nigel Lawson, that the world’s average temperature has fallen in the past 10 years was based on an “erroneous” temperature chart, his think tank, the Global Warming Policy Foundation, has admitted.

The former Tory Chancellor was interviewed on BBC Radio 4’s Today programme about the release of former US Vice-President Al Gore’s new film, The Inconvenient Sequel: Truth to Power, which describes how climate change is already having significant effects on the planet but also that the plunging cost of renewable energy means there is a solution.

The film points out the world’s average temperature had hit the highest on record for three years in a row – 2014, 2015 and 2016 – and an increase in extreme weather events.

His first film in 2006, An Inconvenient Truth, predicted that site of the 9/11 memorial would face an increased risk of being flooded as sea levels rise. At the time, this prompted some ridicule, but this actually happened during Hurricane Sandy in 2012.

Lord Lawson claimed in the interview that the Intergovernmental Panel on Climate Change (IPCC) had “confirmed that there has been no increase in extreme weather events”.

And he then added: “As for the temperature itself, it is striking, he [Gore] made his previous film 10 years ago, and according – again – to the official figures, during this past 10 years, if anything, mean global temperature, average world temperature, has slightly declined.”

However the Global Warming Policy Foundation (GWPF) has now revealed the source of these supposedly “official” figures was a meteorologist who works for a libertarian think tank, the Cato Institute, founded by US billionaire and leading climate sceptic, Charles Koch.

And the GWPF also admitted the figures were wrong.

“It has been brought to our attention that a temperature chart prepared by US meteorologist Ryan Maue and published by Joe Bastardi and which was referred to in the Today programme appearance of Lord Lawson is erroneous,” the think tank tweeted.

“This has been acknowledged in recent days by those responsible for the dataset. We are therefore happy to correct the record.”

Records kept by the UK’s Met Office, Nasa, and the US National Oceanic and Atmospheric Administration are broadly in agreement despite using different temperature stations: the average global temperature is now about one degree Celsius above levels in the late 1800s.

And, just as Al Gore said, the temperature has reached the highest recorded level in the last three successive years.

The GWPF added that it stood by Lord Lawson’s claims that the IPCC agreed there had been no increase in extreme weather.

It is difficult to attribute any single storm or heatwave to the effect of global warming.

However, the latest IPCC report says: “It is likely that the frequency of heat waves has increased in large parts of Europe, Asia and Australia.