Heatwave blamed on climate change

The fingerprints of climate change are all over the intense heat waves gripping the globe this month, a new study finds. Researchers say the deadly hot spells in the American southwest and southern Europe could not have happened without the continuing buildup of warming gases in the air.

These unusually strong heat waves are becoming more common, the study said. The same research found the increase in heat-trapping gases, largely from the burning of coal, oil and natural gas has made another heat wave - the one in China - 50 times more likely with the potential to occur every five years or so.

A stagnant atmosphere, warmed by carbon dioxide and other gases, also made the European heat wave 2.5 degrees Celsius hotter, the one in the United States and Mexico two degrees warmer and the one in China one one degree toastier.

Several scientists, using tree rings and other stand-ins for temperature records, say this month's heat is likely the hottest Earth has been in about 120,000 years, easily the hottest of human civilization.

"Had there been no climate change, such an event would almost never have occurred," said study lead author Mariam Zachariah, a climate scientist at Imperial College of London. She called heat waves in Europe and north America "virtually impossible" without the increase in heat from the mid 1800s. Statistically, the one in China could have happened without global warming.

Since the advent of industrial-scale burning, the world has warmed 1.2 degrees, so "they are not rare in today's climate and the role of climate change is absolutely overwhelming," said her colleague Friederike Otto, who leads a team of volunteer international scientists at World Weather Attribution who do these studies.

But the climate is not stabilized, even at this level. If it warms a few more tenths of a degree, this month's heat will become even more common, Otto said. Phoenix has had a record-shattering 25 straight days of temperatures at or above 43.3 degrees and more than a week when the nighttime temperature never dropped below 32.2 Celsius.

The heat in Spain, Italy, Greece and some Balkan states is likely to reoccur every decade in the current climate.