Scientists say the good news is that Mother Nature has burped and given us a brief reprieve from global warming. The bad news is that the spurt of moderate volcanic activity we have seen over the last 15 years is unlikely to continue, and the massive amount of gas and particulate matter emitted only mitigated around one-third of the impact on man-made global warming.
Volcanic activity cooling the atmosphere
Volcanic activity works to cool the atmosphere because of the sulfur dioxide gas and particles blown out during eruptions. Sulfuric acid forms in tiny droplets when the gas mixes with oxygen in the atmosphere. These droplets can stay suspended in the atmosphere for months, bouncing incoming sunlight away from Earth, resulting in lower temperatures at the surface.
Earlier climate research highlighted that early 21st-century volcanic eruptions could account for a third of the recent global warming hiatus, and this new research confirms this hypothesis.
The new study was published over the weekend in the the online journal Geophysical Research Letters. The research “further identifies observational climate signals caused by recent volcanic activity.” Lawrence Livermore National Laboratory notes that the new study “complements an earlier GRL paper published in November, which relied on a combination of ground, air and satellite measurements, indicating that a series of small 21st-century volcanic eruptions deflected substantially more solar radiation than previously estimated.”
Statement from lead researcher
“This new work shows that the climate signals of late 20th- and early 21st-century volcanic activity can be detected in a variety of different observational data sets,” explained Benjamin Santer, a Lawrence Livermore National Laboratory scientist and the lead author of the study.
Details on new global warming hiatus study
The current research builds on a seminal 2011 study. Santer, co-lead researcher David Ridley (MIT) and teams discovered the key interaction occurs in the stratosphere and the troposphere — the lowest layer of the atmosphere. Those layers divide around six to nine miles (10-15 km) above the Earth.
For technical reasons, satellite measurements of sulfuric acid droplets and aerosols produced by erupting volcanoes can only be made above 15 km. Cirrus clouds interfere with satellite aerosol measurements below 15 km. Therefore, in areas where the lower stratosphere reached down to 10 km, the satellite measurements were missing a big partof the total volcanic aerosol loading.
Santer and Ridley solved the problem by using combined observations from ground-, air- and space-based instruments to more thoroughly observe aerosols in the lower portion of the stratosphere. These improved estimates of total volcanic aerosols suggest that volcanoes may have caused cooling of 0.05 degrees to 0.12 degrees Celsius since the turn of the century.