ClimateWatch Magazine » Climate Patterns & 2010 Temperatures

Climate Patterns & 2010 Temperatures

Adapted from the State of the Climate in 2010 report

August 9, 2011

Near-Record Warmth, Strong Natural Variability

In part due to long-term climate change, global average surface temperature in 2010 was one of the two warmest years on record. Throughout the year, two of the world’s major natural climate patterns—the El Niño-Southern Oscillation and the Arctic Oscillation—also affected temperatures across much of the globe (related video).

El Niño & La Niña
Warm sea and land surface temperatures worldwide were at least partly related to the strong El Niño climate pattern in the eastern tropical Pacific Ocean during the first half of 2010. Combined with a decades-long warming trend, El Niño’s warm water and related air patterns helped make the first half of 2010 one of the two warmest January-to-June periods on record (related image).

The El Niño climate pattern persisted through April, but sea surface temperatures then declined rapidly across the tropical Pacific Ocean, giving way to La Niña conditions. By July, La Niña was well established, and by the end of 2010, it had intensified to a moderate-to-strong La Niña (related video).

Despite the rapid development and strength of the La Niña climate pattern, global average sea surface temperatures remained relatively high throughout 2010. Above-average sea surface temperatures prevailed across the Atlantic and Indian Oceans, with the most dramatic warmth across the tropical Atlantic. This warmth contributed to the heightened activity of the 2010 Atlantic hurricane season as well as to the high risk of coral bleaching across the Caribbean.

Arctic Oscillation
El Niño and La Niña have their biggest influence in the tropics and sub-tropics. In contrast, the Arctic Oscillation is an atmospheric climate pattern that affects large parts of the Northern Hemisphere. When the pattern is “positive,” a strong polar jet stream tends to keep chilly Arctic air confined to northern latitudes.

When the Arctic Oscillation switches to its negative phase, as it did throughout most of 2010, the polar jet weakens, and frigid air spills out of the Arctic more often. In turn, warmer air from lower latitudes flows northward. This “atmospheric swap” can give northern locations unusually mild winters and more southern locations unusually harsh ones (related video).

In 2010, the Arctic Oscillation contributed to unusually cold temperatures over much of northern Eurasia and parts of the United States and unusually warm temperatures in eastern Canada and parts of Greenland.

References
Sánchez-Lugo, A., Kennedy, J.J., and Berrisford, P. (2011). [Chapter 2: Global Climate] Surface Temperature. In “State of the Climate in 2010,” Bulletin of the American Meteorological Society, 92 (6), S36–S38.