Given this, why are opponents so convinced the new runway is a bad idea?

The key word in the commission’s report is “could”. It goes on to say: “Any change to UK’s aviation capacity would have to take place in the context of global climate change, and the UK’s policy obligations in this area.”

Essentially, the chances of meeting the targets after the new runway is in place are very slim.

In a letter addressed to Mr Grayling, Lord Deben and Baroness Brown of Cambridge from the CCC reminded the transport secretary of the essential place aviation plays in meeting the government’s targets under the Climate Change Act and the Paris climate agreement.

The CCC stated the economy-wide target of reducing emissions by 80 per cent below 1990 levels could be achieved only if emissions from the UK aviation industry do not exceed 37.5 million tons – the level seen in 2005.

However, a report released by the Department for Transport has already revealed that aviation emissions will hit 43 million tons by 2030 if the Heathrow expansion goes ahead.

Even when aiming for 2005 levels, the CCC predicts other sectors would have to reduce their emissions by more than 80 per cent and described the targets as “at the upper end of what is currently expected to be deliverable”.