Lower atmospheric dust content behind Atlantic temperature rise?

A study by researchers at the University of Wisconsin at Madison suggests that the recent increase in surface temperature in the Atlantic Ocean has more to do with temporary variations in aerosol content in the atmosphere than due to climate change.

Climate scientists say that an increase in global surface temperatures, due to climate change, will lead to increased frequency and intensity of tropical storms in the 21st century.

Tropical cyclones occur when several conditions are met. Two of these are an abundant source of moisture and ocean surface temperature that exceeds 26 degrees Centigrade.

Scientists have observed a recent increase in the intensity of tropical cyclones. This increase is attributed to increased ocean surface temperature due to climate change. The fourth assessment report of the Intergovernmental Panel on Climate Change (IPCC) confirms this and predicts that this trend will increase in the 21st century.

Not everyone believes that climate change is behind increased ocean surface temperatures. The link between climate change and tropical storms is a hotly debated issue. The present study shows that an increase in frequency of hurricanes could also be due to other factors like a temporary decrease in aerosol content in the atmosphere.

Aerosols are fine dust particles or droplets that float in the air. Aerosols in the earth's atmosphere have natural as well as man made sources. Natural sources of aerosols include volcanic eruptions while man made sources include automobiles and sprays.

Generally, increased aerosol content in the atmosphere leads to a slight cooling trend. The most recent example of this was after the catastrophic eruption of the Krakatau volcano in Indonesia in 1883. Massive amounts of volcanic dust and ash were released into the atmosphere, resulting in less sunlight reaching the earth's surface and a decrease in global surface temperature by about 1 degree Centigrade.

Conversely, a decrease in aerosol content could also lead to a rise in surface temperature. The researchers carried out an extensive study using 26 years of satellite data to see whether such a temporary variation of aerosol content is behind the increasing surface temperature in the northern tropical Atlantic ocean.

They found that upto 70 percent of this trend could be attributed to a decrease in aerosols. “Our results suggest that 69% of the recent upward trend, and 67% of the detrended and 5-year low pass filtered variance, in northern tropical Atlantic Ocean temperatures is the mixed layer’s response to regional variability in aerosols,” said the summary of the study, which was published in the journal Science on March 26.