The average temperature of the Earth has risen over the past century, and it is expected to increase further over the next century. As a result, it is predicted our winters will become warmer. While many studies have suggested this will significantly reduce the number of cold-related deaths that occur in winter months, new research finds this may not be the case.
Lead study author Patrick Kinney, professor of Environmental Health Sciences at Columbia University’s Mailman School of Public Health in New York, NY, and his team publish their findings in the journal Environmental Research Letters.
According to the US Environmental Protection Agency (EPA), the past 100 years have seen the average temperature of the Earth rise by 1.4°F to 9.5°F. Such an increase has already led to noticeable changes in climate and weather, with many regions around the world – including the US – experiencing more frequent droughts, floods and intense heat waves.
Over the next 100 years, the Earth’s temperature is predicted to increase further, to 11.5°F. While this is expected to present a number of environmental and societal challenges, past studies have suggested there may be a positive side to global warming – fewer deaths in winter.
But Prof. Kinney and colleagues have challenged such findings with their latest research. Their analysis of temperature and mortality data from 39 cities in the US and France suggests a warmer climate is unlikely to reduce mortality rates during winter months, primarily because cold temperatures are not directly responsible for excess winter deaths.
The team’s analysis included 1985-2006 data from 36 cities in the US – including New York and Miami – and 1971-2006 data from three cities in France – Paris, Lyon and Marseille.
The researchers assessed daily temperature and mortality data from each city, comparing the number of deaths that occurred in cities that are colder in winter months with those that occurred in cities that are warmer in winter.
Cities with warmer winters were found to have similar winter mortality rates than those with colder winters, which the team says suggests “temperature is not a key driver of winter excess mortality.”
“If cold temperatures were directly responsible for winter mortality, one might expect a more pronounced relative winter mortality excess in cities where winter to summer temperature differences are larger, or where winter temperatures are colder,” note the authors, adding:
“Our findings suggest that reductions in cold-related mortality under warming climate may be much smaller than some have assumed. This should be of interest to researchers and policy makers concerned with projecting future health effects of climate change and developing relevant adaptation strategies.”
Rather than cold temperatures, the researchers suggest there are a number of other factors that may contribute to excess mortality in winter months.
They note that influenza is a risk factor for winter mortality, noting that time spent indoors, school schedules, holiday gatherings, overweight, lack of exercise and air moisture content can raise the risk of flu and other respiratory infections during winter months.
As such, Prof. Kinney and his team say global warming is likely to have “little benefit” if factors such as these are the primary drivers of winter deaths.
The study is subject to some limitations. For example, the researchers were unable to determine the causes of death and did not analyze data by age, sex, ethnicity or economic status. “Thus we were unable to assess the extent to which cold temperatures may differentially affect certain causes or population subgroups that may be more vulnerable,” the authors note.
Contrary to these latest findings, in May, Medical News Today reported on a study published in The Lancet in which researchers claim cold temperatures are the biggest cause of climate-related deaths, killing 20 times as many people as hot weather.