The 15 hottest days, in the world's hottest month

By the end of the week, it is likely that 15 days just this month will have breached an unprecedented global temperature threshold — a clarion wakeup call in the form of extreme weather.

Why it matters: Nearly every facet of the climate system is flashing red this summer, from record-low sea ice extent in Antarctica to hot tub-like ocean waters surrounding South Florida, and all-time high temperature records set in multiple countries on at least three continents.

• And all this is occurring as human-caused emissions of greenhouse gases from the burning of fossil fuels and other sources continue to increase, despite the existence of ever-cheaper technologies to generate electricity and power certain modes of transportation.

Zoom in: Already this month, 14 days have recorded surface air temperatures greater than 17°C (62.6°F) — spikes that have not been seen for roughly 125,000 years.

• In fact, Wednesday marked the 17th straight day with global temperatures hotter than any prior days on record.

Several more records are all but certain to fall in the coming weeks:

• July will be the hottest month on Earth since instrument records began in the 19th century.
• The milestone for the hottest summer worldwide is in jeopardy, according to the European Center for Medium-Range Weather Forecasts.
• NOAA and the ECMWF has said additional heat waves are likely in coming weeks, particularly if the dominant weather pattern — featuring multiple, stuck heat domes around the hemisphere — is not disrupted.

By the numbers: The heat domes worldwide have been noteworthy for their duration, expansiveness and severity. This is the case even in places famous for hot weather, where people would normally shrug off a hot stretch.

• The overnight minimum temperature Wednesday morning in Phoenix was a sweltering 97°F, an all time high for that location.
• On Friday, the city is forecast to have its record 20th-straight day with a high temperature of 110°F or greater.
• Austin, Texas, has had 10-straight days with a high temperature of 105°F or greater, an unprecedented streak.

Threat level: This heat is not a mere inconvenience or something to power through.

• It is downright deadly, particularly for vulnerable populations including the elderly, young children, those with chronic illnesses and people without access to air conditioning.
• Early figures on heat-related deaths in parts of the U.S., for example, are starting to emerge, and in coming weeks it is likely these will climb.
• A recent study in the journal Nature Medicine found severe heat waves in Europe last summer killed as many as 61,000 people.

The intrigue: The 17°C demarcation line is not a hard climate boundary beyond which ice sheets will melt and the oceans rise inexorably. Rather, it represents yet another warning — a "Stop, turn back" sign on the march to a more treacherous and less familiar planet.

• It is also the product of a modern but not 100% precise method of carefully estimating the planet's temperature on a daily basis.
• It involves computer model reanalysis, in which data from ships, buoys, surface weather stations, satellites and other sources are crunched and calculated in near-real-time.

What they're saying: Forget about the overused expression, "the new normal," to describe our current climate moment. As Friedericke Otto, a climate scientist at Imperial College London told Axios, "We’re nowhere near a normal."

• "Whenever we stop burning fossil fuels we can begin to figure out what 'normal' means again," Otto said.
• Former NASA climate scientist James Hansen, who rose to prominence by warning the Senate and the American people about the dangers of climate change in the sizzling American summer of 1988, told The Guardian: "We are headed wittingly into the new reality – we knew it was coming."
• He termed humanity "damned fools," saying: "We have to taste it to believe it."

The bottom line: Perhaps this is our taste of the new type of extreme heat, as we transition into even more unstable times. Because this is both one of the hottest summers of our lives, and one of the coolest of the rest of our lives.