Page 9 - APEC CLIMATE CENTER 2025 Annual Report

APEC CLIMATE CENTER 2025 ANNUAL REPORT

State of the

State of the Asia-Pacific Extreme Climate in 2025 Asia-Pacific

Extreme Climate

in 2025

State of the According to the World Meteorological Organization (WMO), 2025 was ranked as the

third-hottest year on record. The global average surface temperature was 1.44°C (±0.13°C)
Asia-Pacific above the 1850–1900 baseline. Furthermore, the average temperature over the last three
years stood at 1.48°C (±0.13°C) above pre-industrial levels, making it the warmest three-
Extreme Climate year period to date. Despite the emergence of La Niña in 2025, global warming persisted
due to the ongoing accumulation of greenhouse gases in the atmosphere.
in 2025
The Copernicus Climate Change Service (C3S) has warned that at the current rate of warm- Fig 2 Distribution of mean 500hPa geopotential height anomalies, January 1–7, 2025
ing, the 1.5°C threshold set by the Paris Agreement could be reached within a decade—a
pace more than 10 years ahead of initial projections. This sustained global warming has Heavy Snowfall in Japan
intensified climate extremes such as heatwaves, heavy snowfall, and torrential rain, lead- In early February 2025, extensive regions across Japan, stretching from Hokkaido in the
ing to severe economic and human losses across the Asia-Pacific region. north to Kyushu in the south, experienced unprecedented cold waves and heavy snowfall.
Notably, on February 3–4, the city of Obihiro in the Tokachi Plain recorded 120 cm of snow
North American Cold Wave within 12 hours—an unprecedented total for a 12-hour period in Japan's observational
In January 2025, two powerful cold waves struck North America. As a result, the average history (Fig. 3).
temperature in the U.S. for January was recorded at -1.6°C, making it the coldest Janu-
ary since 1988. On January 21, wind chill temperatures plummeted to -33.3°C at Chicago The snowfall resulted in the cancellation of approximately 30 flights, affecting about 2,230
O'Hare International Airport and -36.1°C in Rockford. On January 22, record lows were passengers, while expressways and major roads were closed, and train services were sus-
broken in Louisiana, with -15.6°C in Lafayette and -16.7°C in New Iberia, marking the low- pended. Additionally, over 370 schools implemented temporary closures. Cold air moving
est temperatures since 1893 and 1948, respectively. from Siberia toward East Asia bifurcates around the northern mountain ranges of the Ko-
rean Peninsula before converging over the East Sea. The resulting air-sea interaction, driv-
A storm accompanied by heavy snow developed along the Gulf of Mexico, bringing 15–30 en by relatively high sea surface temperatures, formed massive cloud bands that triggered
cm of accumulated snowfall to low-latitude regions, including Louisiana (New Orleans) the heavy snowfall (Fig. 4).
and Alabama (Fig. 1). In early January, a cold front from the Arctic moved south through
Canada and combined with a powerful blizzard. Subsequently, the weakening of the jet Furthermore, a marine heatwave—a sustained rise in sea surface temperatures—was ob-
stream caused a disruption of the polar vortex, allowing frigid air to descend into the served off the coast of Hokkaido. Numerical model experiments indicated that this marine
south-central U.S. and the Gulf Coast. This frigid air collided with warm, moist air masses heatwave augmented precipitation by approximately 50% by facilitating the formation of
1)
moving north from the Gulf of Mexico, leading to unprecedented snowfall in these south- surface fronts and enhancing atmospheric instability .
ern regions. This weakening of the polar vortex is widely attributed to climate change, par-
ticularly high-temperature anomalies in the Arctic (Fig. 2).

1) Hirata, H., K. Tamura, T. Morioka,
and T. Sato, 2025:
Mechanisms behind the record-break-
ing snowfall in Obihiro, Hokkaido,
Japan, in February 2025: Roles of at-
mospheric environment and a marine
Fig 3 Distribution of mean precipitation anomalies, February 1–7, 2025
Fig 1 Distribution of mean surface air temperature anomalies, January 1–7, 2025
heatwave. SOLA, 1-9, 21.
8 8 9 9