Sun-dimming volcanoes partly explain global warming hiatus-study

OSLO Sun Feb 23, 2014 1:06pm EST

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OSLO (Reuters) - 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, a study showed on Sunday.

Eruptions of at least 17 volcanoes since 2000, including Nabro in Eritrea, Kasatochi in Alaska and Merapi in Indonesia, ejected sulfur 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.

TEMPORARY RESPITE

"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 U.N. 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.

For the study, click on: dx.doi.org/10.1038/ngeo2098

(Reporting by Alister Doyle; Editing by Alistair Lyon)

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Comments (11)
KyleZ wrote:
It is sad that people can’t recognize agenda driven science when they see it. These people refuse to accept that the hypothesis is wrong or even exaggerated. It doesn’t matter what the physical evidence suggests, there must be some conspiracy by nature to perfectly cover up global warming and they just have to be detectives and find where it is hiding.

The hiatus doesn’t exist, no weak trade winds are causing the hiatus, no the hiatus doesn’t exist, no strong trade winds are causing the hiatus, no the hiatus doesn’t exist, the sun is not a cause of global warming it has little to no effect, no the fewer sunspots is causing the hiatus, no global warming itself is causing the hiatus by melting sea ice even though there is globally more sea ice when you include the southern pole. But the Antarctic sea ice growth isn’t statistically significant, but no now it is growing but it is from higher winds at the pole, no it isn’t growing just the surface area is expanding but the depth is shrinking, no it is getting thicker too but the southern pole was never predicted to lose ice in the first place(it was). The hiatus doesn’t exist, no the oceans are absorbing the heat, no the ocean temperature rise does not adequately explain the hiatus but because there is no hiatus temperatures are still rising, no the oceans do explain it the heat is just hiding at depths below where our sensors can detect it.

They (rightfully) trash people who say global warming can’t be happening because it was cold this week, but then are hypocrites and come out after every hurricane or heatwave to say “see look how bad global warming is making things.” They say hurricanes are getting worse, when they are in fact not changing or even getting weaker. This is the longest stretch without a category 3 or greater making landfall in North America and there are no more hurricanes today then there were 50 years ago, in fact there may be less. Can no one see this has gone too far? I used to be completely sold on catastrophic global warming. But I am sorry I can see this for what it is now, and it isn’t objective science. These people showed their true colors. These scientists are acting far more like politicians that lie and tell half truths than scientists that hold truth above all else, even above personal glory, money and ego.

Feb 23, 2014 3:06pm EST  --  Report as abuse
kehvan wrote:
So, what was once derided as skeptic fantasies is now being rationalized.

Feb 23, 2014 4:59pm EST  --  Report as abuse
KyleZ wrote:
It is sad that people can’t recognize agenda driven science when they see it. These people refuse to accept that the hypothesis is wrong or even exaggerated. It doesn’t matter what the physical evidence suggests, there must be some conspiracy by nature to perfectly cover up global warming and they just have to be detectives and find where it is hiding.

The hiatus doesn’t exist, no weak trade winds are causing the hiatus, no the hiatus doesn’t exist, no strong trade winds are causing the hiatus, no the hiatus doesn’t exist, the sun is not a cause of global warming it has little to no effect, no the fewer sunspots is causing the hiatus, no global warming itself is causing the hiatus by melting sea ice even though there is globally more sea ice when you include the southern pole. But the Antarctic sea ice growth isn’t statistically significant, but no now it is growing but it is from higher winds at the pole, no it isn’t growing just the surface area is expanding but the depth is shrinking, no it is getting thicker too but the southern pole was never predicted to lose ice in the first place(it was). The hiatus doesn’t exist, no the oceans are absorbing the heat, no the ocean temperature rise does not adequately explain the hiatus but because there is no hiatus temperatures are still rising, no the oceans do explain it the heat is just hiding at depths below where our sensors can detect it.

They (rightfully) trash people who say global warming can’t be happening because it was cold this week, but then are hypocrites and come out after every hurricane or heatwave to say “see look how bad global warming is making things.” They say hurricanes are getting worse, when they are in fact not changing or even getting weaker. This is the longest stretch without a category 3 or greater making landfall in North America and there are no more hurricanes today then there were 50 years ago, in fact there may be less. Can no one see this has gone too far? I used to be completely sold on catastrophic global warming. But I am sorry I can see this for what it is now, and it isn’t objective science. These people showed their true colors. These scientists are acting far more like politicians that lie and tell half truths than scientists that hold truth above all else, even above personal glory, money and ego. They don’t know why exactly the earth hasn’t been warming the last 17 years but claim they absolutely KNOW why it was warming and that it was all from people? Some settled science.

Feb 23, 2014 7:10pm EST  --  Report as abuse
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