http://www.odt.co.nz/news/world/292773/sun-dimming-volcanoes-slow-global-warming-study
Eruptions of at least 17 volcanoes since 2000, including Nabro in Eritrea,
Kasatochi in Alaska and Merapi in Indonesia, ejected sulphur whose
sun-blocking effect had been largely ignored until now by climate
scientists, it said.
Sun-dimming volcanoes slow global warming - study
Mon, 24 Feb 2014
Small volcanic eruptions help explain a hiatus in global warming this
century by dimming sunlight and offsetting a rise in emissions of
heat-trapping gases to record highs, according to a new study.
Eruptions of at least 17 volcanoes since 2000, including Nabro in Eritrea,
Kasatochi in Alaska and Merapi in Indonesia, ejected sulphur whose
sun-blocking effect had been largely ignored until now by climate
scientists, it said.
The pace of rising world surface temperatures has slowed since an
exceptionally warm 1998, heartening those who doubt that an urgent,
trillion-dollar shift to renewable energies from fossil fuels is needed to
counter global warming.
Explaining the hiatus could bolster support for a U.N. climate deal, due to
be agreed by almost 200 governments at a summit in Paris in late 2015 to
avert ever more floods, droughts, heatwaves and rising sea levels.
"This is a complex detective story," said Benjamin Santer of the Lawrence
Livermore National Laboratory in California, lead author of the study in
the journal Nature Geoscience that gives the most detailed account yet of
the cooling impact of volcanoes.
"Volcanoes are part of the answer but there's no factor that is solely
responsible for the hiatus," he told Reuters of the study by a team of U.S.
and Canadian experts.
Volcanoes are a wild card for climate change - they cannot be predicted and
big eruptions, most recently of Mount Pinatubo in the Philippines in 1991,
can dim global sunshine for years.
Santer said other factors such as a decline in the sun's output, linked to
a natural cycle of sunspots, or rising Chinese emissions of sun-blocking
pollution could also help explain the recent slowdown in warming.
The study suggested that volcanoes accounted for up to 15 percent of the
difference between predicted and observed warming this century. All things
being equal, temperatures should rise because greenhouse gas emissions have
hit repeated highs.
"Volcanoes give us only a temporary respite from the relentless warming
pressure of continued increases in carbon dioxide," said Piers Forster,
Professor of Climate Change at the University of Leeds.
A study by the UN Intergovernmental Panel on Climate Change last year
suggested that natural variations in the climate, such as an extra uptake
of heat by the oceans, could help explain the warming slowdown at the
planet's surface.
The IPCC projected a resumption of warming in coming years and said that
"substantial and sustained" cuts in greenhouse gas emissions were needed to
counter climate change.
It also raised the probability that human activities were the main cause of
warming since 1950 to at least 95 percent from 90 in 2007. Despite the
hiatus, temperatures have continued to rise - 13 of the 14 warmest years on
record have been this century, according to the World Meteorological
Organisation.
Received on Sun Feb 23 2014 - 20:13:59 EST