The onset of La Niña in the tropical Pacific Ocean has caused temperatures drop to levels not seen in six years, according to satellite temperature data.
“Note that La Niña cooling in the tropics has finally penetrated the troposphere, with a -0.12 deg. C departure from average,” wrote atmospheric scientists John Christy and Roy Spencer, who compile satellite data at the University of Alabama, Huntsville.
Satellite data, which measures Earth’s bulk atmosphere, show temperature anomalies dropped from 0.41 degrees Celsius in December to 0.26 degrees in January. The temperature drop was brought about by a La Niña cooling event in the tropics.
La Niña is in full swing in 2018, plunging temperatures in the tropics to -0.12 degrees Celsius in January, down from 0.26 degrees the previous month. It’s the third-largest tropical temperature drop on record.
“The last time the tropics were cooler than this was June, 2012 (-0.15 deg. C),” the scientists wrote.
“Out of the 470 month satellite record, the 0.38 deg. C one-month drop in January tropical temperatures was tied for the 3rd largest, beaten only by October 1991 (0.51 deg. C drop) and August, 2014 (0.41 deg. C drop),” they wrote.
La Niña settled in late 2017, with cooler waters reaching from South America, across to eastern Pacific islands. It’s the opposite of El Niño warming events.
“The last time the Southern Hemisphere was this cool (+0.06 deg. C) was July, 2015 (+0.04 deg. C),” Christy and Spencer wrote.
“The linear temperature trend of the global average lower tropospheric temperature anomalies from January 1979 through January 2018 remains at +0.13 C/decade,” they wrote.