Volcanoes contribute to recent warming ‘hiatus’

Date:

Share post:

Volcanic eruptions in the early part of the 21st century have cooled the planet, according to a study led by Lawrence Livermore National Laboratory. This cooling partly offset the warming produced by greenhouse gases.

Volcanoes contribute to recent warming 'hiatus'
LLNL scientist Benjamin Santer and his climbing group ascend Mt. St. Helens via the “Dogshead Route” in April 1980, about a month before its major eruption. The group was the last to reach the summit of Mt. St. Helens before its major eruption that May. New research by Santer and his colleagues shows that volcanic eruptions contribute to a recent warming “hiatus” [Credit: DOE/Lawrence Livermore National Laboratory]

Despite continuing increases in atmospheric levels of greenhouse gases, and in the total heat content of the ocean, global-mean temperatures at the surface of the planet and in the troposphere (the lowest portion of Earth’s atmosphere) have shown relatively little warming since 1998. This so-called ‘slow-down’ or ‘hiatus’ has received considerable scientific, political and popular attention. The volcanic contribution to the ‘slow-down’ is the subject of a new paper appearing in the Feb. 23 edition of the journal Nature Geoscience.

Volcanic eruptions inject sulfur dioxide gas into the atmosphere. If the eruptions are large enough to add sulfur dioxide to the stratosphere (the atmospheric layer above the troposphere), the gas forms tiny droplets of sulfuric acid, also known as “volcanic aerosols.” These droplets reflect some portion of the incoming sunlight back into space, cooling 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,” said Lawrence Livermore climate scientist Benjamin Santer, who serves as lead author of the study. “This has created a natural cooling of the planet and has partly offset the increase in surface and atmospheric temperatures due to human influence.”

From 2000-2012, emissions of greenhouse gases into the atmosphere have increased — as they have done since the Industrial Revolution. This human-induced change typically causes the troposphere to warm and the stratosphere to cool. In contrast, large volcanic eruptions cool the troposphere and warm the stratosphere. The researchers report that early 21st century volcanic eruptions have contributed to this recent “warming hiatus,” and that most climate models have not accurately accounted for this effect.

“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.”

The researchers performed two different statistical tests to determine whether recent volcanic eruptions have cooling effects that can be distinguished from the intrinsic variability of the climate. The team found evidence for significant correlations between volcanic aerosol observations and satellite-based estimates of lower tropospheric temperatures as well as the sunlight reflected back to space by the aerosol particles.

“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, the Ellen Swallow Richards 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 Earth cooler.”

The research is funded by the Department of Energy’s Office of Biological and Environmental Science in the Office of Science. The research involved a large, interdisciplinary team of researchers with expertise in climate modeling, satellite data, stratospheric dynamics and volcanic effects on climate, model evaluation and computer science.

Author: Anne M Stark | Source: DOE/Lawrence Livermore National Laboratory [February 24, 2014]

ADVERTISEMENT

spot_img

Related articles

Archaeogenetic findings unlock ancestral origins of Sardinians

The island of Sardinia is remarkable for the fact that an exceptionally high proportion of the population is...

Extinct owl species discovered in Madeira

An international team of scientists, including some from Majorca and the Canary Islands, have described a new type...

Seeking Korea’s earliest inhabitants

University of Hawaiʻi at Mānoa Assistant Professor Christopher Bae was born in Seoul but lost his parents as...

Ruins of 2,000-year-old city found near Peshawar

The first phase of excavation at the 2,000-year-old city of Pashkalavati, near Charsadda, about 25 miles from here,...

Human transport has unpredictable genetic and evolutionary consequences for marine species

New research, led by the University of Southampton, has found that human activities such as shipping are having...

Ancient Italian fossils reveal risk of parasitic infections due to climate change

In 2014, a team of researchers led by a paleobiologist from the University of Missouri found that clams...

Statue of Hermes uncovered in SW Turkey

A bronze Hermes statue from the Roman era, which has been unearthed during excavations in the ancient city...

Study reveals deep ties between diverse tropical rainforests revealed

Tropical rainforests play a vital role in the well-being of our planet, soaking up carbon dioxide and helping...