Saturday’s steamy 84-degree reading was posted in Arkhangelsk, Russia, where the average high temperature is around 54 this time of year. The city of 350,000 people sits next to the White Sea, which feeds into the Arctic Ocean’s Barents Sea.

In Koynas, a rural area to the east of Arkhangelsk, it was even hotter on Sunday, soaring to 87 degrees (31 Celsius). Many locations in Russia, from the Kazakhstan border to the White Sea, set record-high temperatures over the weekend, some 30 to 40 degrees (around 20 Celsius) above average. The warmth also bled west into Finland, which hit 77 degrees (25 Celsius) Saturday, the country’s warmest temperature of the season so far.

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The abnormally warm conditions in this region stemmed from a bulging zone of high pressure centered over western Russia. This particular heat wave, while a manifestation of the arrangement of weather systems and fluctuations in the jet stream, fits into what has been an unusually warm year across the Arctic and most of the mid-latitudes.

Across the Arctic overall, the extent of sea ice has hovered near a record low for weeks.

Data from the Japan Meteorological Agency show April was the second warmest on record for the entire planet.

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These changes all have occurred against the backdrop of unremitting increases in carbon dioxide, which has now crossed another symbolic threshold.

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Saturday’s carbon dioxide measurement of 415 parts per million at Hawaii’s Mauna Loa Observatory is the highest in at least 800,000 years and probably over 3 million years. Carbon dioxide levels have risen by nearly 50 percent since the Industrial Revolution.

The clip at which carbon dioxide has built up in the atmosphere has risen in recent years. Ralph Keeling, director of the program that monitors the gas at the Scripps Institution of Oceanography, tweeted that its accumulation in the last year is “on the high end.”

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Carbon dioxide is a greenhouse gas that, along with the rise of several other such heat-trapping gases, is the primary cause of climate warming in recent decades, scientists have concluded.

Eighteen of the 19 warmest years on record for the planet have occurred since 2000, and we keep observing these highly unusual and often record-breaking high temperatures.

They won’t stop soon, but cuts to greenhouse emissions would eventually slow them down.