The hotter the day the more likely US immigration judges are to make harsher decisions – a new study by the universities of Ottawa, Canada and Sussex, England can reveal.

The study, published in the American Economic Journal: Applied Economics, analyses the impact of outdoor temperatures on high-stakes decisions made in 207,000 US immigration cases.

The academics discovered that when there was a 10 ◦F degree increase in the outside temperature on case day, US judges made decisions less favourable to the applicant in nearly 15,000 cases, despite judgements being made indoors and ‘protected’ by climate-control.

This is the first time researchers have shown that the same-day outdoor temperature influences the decisions people make indoors – even if they in a naturally-occurring or artificial setting.

The results support previous research which show links between the temperature of the day and people’s appetite for taking risks.

Professor Anthony Heyes, part-time Professor of Economics at University of Sussex and Canada Research Chair at University of Ottawa, said: “For the first time ever we show there is a link between the decisions people make indoors and the temperature outdoors.

“With the global average temperature continuing to rise it is vital we understand these links so we can best work out how climate change will affect human well-being.”

Professor Soodeh Saberian, from the Assistant Professor in the Department of Economics at the University of Manitoba, said: “The study shows the important ways in which what is going on with temperature outside can have a really striking influence on how well-trained professional do their jobs, even when they are working indoors and enjoy really good quality air-conditioning.

“It counters the complacent but often heard that as temperatures get hotter and hotter we can simply insulate ourselves from the effects of that by moving indoors and using better quality air-conditioning. That might help a bit, but it doesn't put an end to the problem".