|Volcanoes Slow Global Warming|
Gigantic emissions of hot gasses and viscous flows of lava from volcanic eruptions have ironically cooled Earth and stalled global warming.
Despite continuing growth in atmospheric levels of greenhouse gases, and rising temperatures in the oceans, global-mean temperatures at the surface of the planet and in the troposphere (the lowest portion of the Earth's atmosphere) have shown relatively little warming since 1998.
Researchers at Lawrence Livermore National Laboratory believe this 'slow-down' or 'hiatus' is largely due to a series of volcanic eruptions in the early part of the 21st century.
These droplets reflect some portion of the incoming sunlight back into space, cooling the Earth's surface and the lower atmosphere.
"In the last decade, the amount of volcanic aerosol in the stratosphere has increased, so more sunlight is being reflected back into space," says Lawrence Livermore climate scientist Benjamin Santer. "This has created a natural cooling of the planet and has partly offset the increase in surface and atmospheric temperatures due to human influence."
"The recent slow-down in observed surface and tropospheric warming is a fascinating detective story," Santer said. "There is not a single culprit, as some scientists have claimed. Multiple factors are implicated. One is the temporary cooling effect of internal climate noise. Other factors are the external cooling influences of 21st century volcanic activity, an unusually low and long minimum in the last solar cycle, and an uptick in Chinese emissions of sulfur dioxide.
"The real scientific challenge is to obtain hard quantitative estimates of the contributions of each of these factors to the slow-down."
"This is the most comprehensive observational evaluation of the role of volcanic activity on climate in the early part of the 21st century," said co-author Susan Solomon, professor of atmospheric chemistry and climate science at MIT. "We assess the contributions of volcanoes on temperatures in the troposphere - the lowest layer of the atmosphere -- and find they've certainly played some role in keeping the Earth cooler."
Lawrence Livermore National Laboratory