Today's Learning 67 (Abnormally High Temperatures)

Yesterday, temperatures rose nationwide, and with maximum temperatures in Miyagi Prefecture exceeding 20°C, reaching levels typical of late September, it was record-breaking warmth.

While not believed in conspiracy theory circles,
it is generally attributed to the following causes.

1. Meandering of the Westerlies (Jet Stream)

The westerlies, which normally trap cold air at the North Pole, have weakened and are meandering significantly.
• When they meander, warm air pushes northward, causing air similar to early spring to flow into the vicinity of Japan.
• Result: Temperatures become abnormally high even in winter.

2. Arctic Warming (Arctic Amplification)

The Arctic is warming at two to four times the global average rate.
• The Arctic warms
• The temperature difference between north and south decreases
• The westerlies weaken and become more prone to meandering
👉 This is the cause of the increase in extremes, such as abnormally high temperatures and cold waves.

3. Abnormal Configuration of Pacific and Continental High-Pressure Systems

Unusually for this time of year,
• the Pacific high-pressure system is not weakening, and
• strong cold air from the continent is not moving southward
— a shift in atmospheric pressure patterns is occurring.

4. Rise in Sea Surface Temperatures

When sea surface temperatures near Japan are higher than average,
• warm, moist air is easily generated
• and because temperatures do not drop easily at night, it feels "abnormally" warm.

5. Global Warming is "Adding a Platform"

It is not just natural phenomena; global warming is raising the overall baseline,
so that phenomena that would have been considered "a little warm" in the past are now record-breaking high temperatures.

In summary

Because the disturbance of the westerlies × Arctic warming × abnormal pressure patterns × rising sea temperatures
are occurring simultaneously, this abnormal high temperature for this time of year is happening.

Is this phenomenon only for this year❓

To start with the conclusion,
the reality is that "rather than just this year being special, years prone to abnormally high temperatures are increasing."

■ This year is certainly "stronger," but it is not a one-off event

　This year's warmth is notable in that
• temperatures are high for the time of year
• there are many record updates. However, the important point is that similar things have been happening consecutively in 2023, 2024,
and this year.

■ Differences from the past (this is the decisive factor)

Past (20–30 years ago)
• "There is a warm winter occasionally"
• The following year returns to a normal cold winter

Now
• Warm winters and abnormally high temperatures are candidates every year, not every few years
• "Average" years are becoming fewer

👉 This is because the base temperature has risen.

■ What are the characteristics of this year?

This year, in particular, conditions such as
• The meandering of the westerlies has continued for a long period • There is a significant decrease in Arctic sea ice • Sea surface temperatures have remained extremely high
have overlapped, making this a year where "abnormalities remain abnormal for a long time."

■ What will happen in the future?

The common consensus among experts is:
• "It is unlikely to end with just this year" • Expect warm winters followed by sudden cold waves • Seasons arriving earlier • Spring and autumn becoming shorter
Because a climate with large fluctuations has become the norm,

while this year is particularly "severe," we have entered an era where abnormally high temperatures themselves are no longer rare.