Pessimism is probably “a bigger problem than climate change”, said the novelist Ian McEwan on Monday afternoon, as temperatures broke May records in the UK.

McEwan “constantly” hears people say that they don’t “expect their children to have as good a life as they did”, but suggested that optimism is a “moral duty”.

McEwan’s latest book, What We Can Know, is partly set in 2119, in a Britain submerged by seas. He spoke at the Hay festival on a panel alongside the former NFU president Minette Batters and Sandi Toksvig, on a day that saw temperatures in London reach 34.8C, beating a May record set in 1922.

McEwan went on to say that optimism is an “exercise in rationality”, because it’s “quite possible” – given that “the world is big, cultures are diverse” – that “there could be a revolution happening and we don’t even know about it”. He referred to the “historical moment” in 2020 when electricity generated from renewable sources outpaced that generated from gas and coal plants in the UK. “We were probably too busy with Covid to even notice,” he said.

He added that “self-interest might be a very good first step” towards progress on the climate crisis. “If you’ve knocked, say, £150 off your annual bill by having a few panels on your balcony – if you happen to have a balcony – the next step will feel slightly virtuous. It’s a nudge, basically.”

Batters, who led the government’s farming profitability review last year, said that farmers “do not know what is coming next” due to extreme weather. “Last year, in my 26 years of farming, I’ve never had a year like it,” she added. “We produced 50% of our normal hay crop, 50% of our normal silage crop.”

Uncertainty for farmers is heightened by “all the political shenanigans, the changes”, she said. Batters’s review highlighted that just 7% of farmers in England fully understand “Defra’s vision for farming”.

“Farmers don’t know what the national plan is, and the government doesn’t know what the individual plans are on the farm,” she continued. Farming has “almost become a game of Russian roulette”. Her decision to grow spring barley this year was akin to “rolling dice”.

Batters also criticised Andy Burnham’s proposal for a land value tax. “When I hear Andy Burnham talking about taxing land around Manchester, I’m just thinking: ‘Oh my goodness,’” she said. “Ten-year waiting lists on allotments, lack of green spaces: can’t we focus on proper land use?”

Asked about HS2, McEwan said that there would be a “huge gain in cutting our losses” and investing money in local services instead.

He also said that the “blessing” of 2,000 years of footpaths in Britain has been “extraordinary”, but that the footpaths are “under a pressure”, adding that “quite powerful, semi-corrupt large landowners can somehow get a footpath closed down by taking the leader of the council out to dinner”.