The UK Met Office has said that the heatwave records in the Western United States are directly attributable to climate change.

The record-breaking heatwave is devastating parts of northwestern North America, and the heat is expected to continue now through much of this week.

Nikos Christidis, climate scientist with the Met Office commented:

“Without human-induced climate change, it would have been almost impossible to hit such record-breaking mean June temperatures in the Western United States as the chances of natural occurrence is once every tens of thousands of years.

“In the present-day climate getting an extremely hot June is common and is likely to occur twice in three decades. However, an analysis from many computer models suggests that by the end of the century these extreme temperatures are more likely than not. Human influence is estimated to have increased the likelihood of a new record several thousand times

Temperatures in parts of the northwest USA and southwest Canada are likely to reach as high as around 45.0°C by day for perhaps five or more days, with extremely warm nights in between.

In the affected area a few thunderstorms and locally gusty winds will bring wildfire risks.

Paul Hutcheon is a meteorologist with the Met Office’s global guidance unit. He said:

“Many all-time long-standing station records are expected to be broken for many days in a row, some by more than 5.0°C. The all-time Canadian record was broken on Sunday, with Lytton in British Columbia recording 46.6°C (1.6°C higher than the previous record set on 5 July 1937). Less than 24 hours later, Lytton broke this record again, reaching 47.9°C on Monday To put this into context the average June maximum is around 24.3°C.”

The heat is also affecting northwestern United States with Seattle setting a new all-time record at 40°C. Portland, in Oregon, broke the record twice: 42.0°C on Saturday and 44.4°C on Sunday, according to the US National Weather Service.

The heat is being driven by a huge ridge of high pressure.

Armel Castellan is a meteorologist with Environment and Climate Change Canada. He said:

“Higher temperatures started in earnest on Friday and it will be peaking early this week for the coast and the middle of the week for the interior of British Columbia, and then the heat will be moving east into Alberta: so we are not done with this yet.

“Northwest Territories have recorded their all-time highest temperatures not just in June, but any point in the year. We are setting records that have no business in being set so early in the season.”

“We have experienced a ridge with low pressure sandwiched on either side. And it’s really hard to move it. The jet stream isn’t moving it along. In that pattern we have essentially a heat dome. A pattern that is sticking to its guns where pollutants and heat keep adding to each other. It is compounding.”

Even at night residents of British Columbia have been struggling to cope with the extreme night-time heat.

Impacts from record-breaking heat expected to be significant

The impacts from the record-breaking heat are expected to be significant. Paul Hutcheon of the Met Office added:

“Significant excess human and animal mortality is likely. In this region properties are generally designed to retain heat, not to shed heat, and air conditioning is much less prevalent than in other parts of North America. These temperatures will also likely stress infrastructure in this region, for example, power and water supplies. Additionally the risk of wildfires will increase throughout this spell. The warmth may well lead to rapid melting of the some mountain snowpack across the region, which could lead to some localised avalanche, flooding, and landslides in the mountains.”

In a statement, the World Meteorological Organization said the early summer hot weather conditions are taking place against the background of human-induced climate change with global temperatures already 1.2 C higher than pre-industrial levels.

Heatwaves are becoming more frequent and intense as greenhouse gas concentrations lead to a rise in global temperatures. They are starting earlier and ending later and are taking an increasing toll on human health and health systems.”