A new study has revealed that extreme heat events are happening more often across the US and Canada, while extreme cold events are on the decline. The research could one day be used to provide an early warning for such weather events, which could allow for the protection of vulnerable crops and at risk populations, such as the elderly and those with chronic illnesses.

Global warming is a serious threat to the future of our species. Since the 1970s, the global mean surface temperature has been steadily increasing, prompting nations across the globe to sign up to accords such as the Paris Agreement.

According to the authors of the study, extreme weather events, such as very hot or cold periods, arguably pose a greater threat to many species and plants than the gradual increase of the global mean surface temperature.

Researchers from Kent State University in Ohio set out to examine these extreme weather events, and analyze how they have changed between 1980 and 2016. The study accounted for absolute extreme temperature events, such as very hot days in the summer, and cold ones in the winter, and also relative extreme temperatures, which are anomalously high or low relative to the norm for a particular season.

The researchers behind the new study state that these relative extreme events are changing faster than absolute weather extremes, and can be damaging both to the environment, and to the people and animals that inhabit it. For example, unexpected hot periods can lead to early thawing in winter snow, and affect the migratory instincts of birds and insects, causing them to leave before there is enough food at their destination.

The study mentions one instance that occurred in March 2012, in which a warm event triggered a "false spring" that coaxed vegetation out of winter dormancy, leaving it unable to cope with subsequent frosts. This incident had a direct effect on the human population in the region, leading to significant agricultural losses.

High-temperature events can also be particularly damaging to vulnerable populations such as children, the elderly and the disabled, if they happen early in the season, as opposed to later in the season when these populations are more acclimatized to higher temperatures.

The team discovered that the number of absolute extreme heat events had increased in the US and Canada since 1980, with a higher occurrence of extremely hot days and abnormally hot winter days in recent years. The uptake in hot temperature events was felt worst in the southeast.

Conversely, there has been a drop-off in extreme cold weather events, which had previously been prevalent in Alaska, Northern Canada and across the North American Atlantic coast.

According to Kristie Ebi, a professor of Environmental and Occupational Health Sciences at the University of Washington, who was not involved in the study, the research could have practical applications in the future.

"Using information generated in the study on regional patterns in extreme weather events, particularly relative extremes in temperature, we could issue early warnings so that people would know what to do to protect themselves, protect crops, and protect ecosystems," comments Abi.

The study has been published in the Journal of Geophysical Research: Atmospheres.