Heat wave in the West 'virtually impossible' without climate change

Last week’s deadly and record-breaking heat wave in parts of the Western U.S. and Canada would have been "virtually impossible" without the influence of climate change, according to a study released Wednesday by leading scientists, who said global warming made the extreme temperatures at least 150 times more likely to occur.

Hundreds of people were reported to have died because of the heat, and the majority of deaths were in British Columbia, Canada. More than 100 people died in Oregon, a death toll described as "horrific" by the state's governor, Kate Brown, USA Today reports.

Study co-author Kristie L. Ebi of the Center for Health and the Global Environment at the University of Washington warned that "in the United States, heat-related mortality is the No. 1 weather-related killer."

Parts of the U.S. and Canada saw temperatures break records by several degrees, including a new all-time Canadian record of 121.3 degrees in the village of Lytton, which was virtually destroyed by a wildfire shortly after setting the record.

Portland, the largest city in Oregon, broke its all-time temperature record for three straight days, topping out at 116 degrees – significantly hotter than the average June highs in the 80s, according to National Weather Service data.

"Climate change is making extremely rare events such as this one become more frequent," said report co-author Sonia Seneviratne of the Institute for Atmospheric and Climate Science at ETH Zurich in a statement.

In fact, every heat wave occurring today is made more likely and more intense by climate change, the study found.

Human-caused climate change, or global warming, is caused by the burning of fossil fuels such as oil, gas and coal, which release greenhouse gases such as carbon dioxide and methane into the Earth's atmosphere and oceans.