Researchers have solved a puzzle which has challenged scientists studying climate change for more than a decade.
Climate models predict that equatorial Pacific trade winds should weaken with increasing greenhouse gases.
Yet since the early 1990s satellites and climate stations reveal a rapid strengthening of the Pacific trade winds, accelerating sea level rise in the western Pacific and impacting both Pacific and global climate.
“The answer to the puzzle is that recent rapid Atlantic Ocean warming has affected climate in the Pacific,” say the scientists.
Their findings from observations and modelling experiments are published in the journal Nature Climate Change.
“We were surprised to find that the main cause of the Pacific wind, temperature, and sea level trends over the past 20 years lies in the Atlantic Ocean,” says Dr Shayne McGregor of the Climate Change Research Centre at the University of New South Wales.
“We saw that the rapid Atlantic surface warming observed since the early 1990s, induced partly by greenhouse gasses, has generated unusually low sea level pressure over the tropical Atlantic.
“This, in turn, produces an upward motion of the overlying air parcels. These parcels move westward aloft and then sink again in the eastern equatorial Pacific, where their sinking creates a high pressure system. The resulting Atlantic–Pacific pressure difference strengthens the Pacific trade winds.”
The increase in these winds has caused eastern tropical Pacific cooling, amplified the Californian drought, accelerated sea level rise three times faster than the global average in the Western Pacific and has slowed the rise of global average surface temperatures since 2001.