Aerosols from Moderate Volcanos Now Blamed for Global Warming Hiatus

While looking for quotes on an upcoming post about Ocean Heat Content, I ran across the press release for a new paper (in press) by Neely et al, which blames the recent slowdown in global warming on smaller more moderate volcanos.


Many readers will recall the October 2011 article by Paul Voosen titled Provoked scientists try to explain lag in global warming.  The article presented the different responses from a number of climate scientists, including John Barnes, Kevin Trenberth, Susan Solomon, Jean-Paul Vernier, Ben Santer, John Daniel, Judith Lean, James Hansen, Martin Wild, and Graeme Stephens, to the question, “Why, despite steadily accumulating greenhouse gases, did the rise of the planet’s temperature stall for the past decade?”  The different replies led Roger Pielke, Sr. to note at the end of his post Candid Comments from Climate Scientists:

These extracts from the Greenwire article illustrate why the climate system is not yet well understood. The science is NOT solved.

Judith Curry provided running commentary in her post Candid Comments from Global Warming Scientists.  If you haven’t read it, it’s a worthwhile read.


Neely et al  2013  (in press) blames moderate volcanos. According to a press release from the University of Colorado Boulder:

A team led by the University of Colorado Boulder looking for clues about why Earth did not warm as much as scientists expected between 2000 and 2010 now thinks the culprits are hiding in plain sight — dozens of volcanoes spewing sulfur dioxide.

The study results essentially exonerate Asia, including India and China, two countries that are estimated to have increased their industrial sulfur dioxide emissions by about 60 percent from 2000 to 2010 through coal burning, said lead study author Ryan Neely, who led the research as part of his CU-Boulder doctoral thesis. Small amounts of sulfur dioxide emissions from Earth’s surface eventually rise 12 to 20 miles into the stratospheric aerosol layer of the atmosphere, where chemical reactions create sulfuric acid and water particles that reflect sunlight back to space, cooling the planet.

The paper (in press) is Neely et al (2013) Recent anthropogenic increases in SO2 from Asia have minimal impact on stratospheric aerosol.

The abstract reads:

Observations suggest that the optical depth of the stratospheric aerosol layer between 20 and 30 km has increased 4–10% per year since 2000, which is significant for Earth’s climate. Contributions to this increase both from moderate volcanic eruptions and from enhanced coal burning in Asia have been suggested. Current observations are insufficient to attribute the contribution of the different sources. Here we use a global climate model coupled to an aerosol microphysical model to partition the contribution of each. We employ model runs that include the increases in anthropogenic sulfur dioxide (SO2) over Asia and the moderate volcanic explosive injections of SO2 observed from 2000 to 2010. Comparison of the model results to observations reveals that moderate volcanic eruptions, rather than anthropogenic influences, are the primary source of the observed increases in stratospheric aerosol.

Bottom line: There’s still no consensus from climate scientists about the cause of the slowdown in the warming rate of global surface temperatures.

And of course, the sea surface temperature and ocean heat content reveal another reason: there hadn’t been a strong El Niño to release monumental volumes of warm water from below the surface of the tropical Pacific and shift up the sea surface temperatures of the Atlantic, Indian and West Pacific Oceans.  Refer to my essay “The Manmade Global Warming Challenge” and my ebook Who Turned on the Heat?

About Bob Tisdale

Research interest: the long-term aftereffects of El Niño and La Nina events on global sea surface temperature and ocean heat content. Author of the ebook Who Turned on the Heat? and regular contributor at WattsUpWithThat.
This entry was posted in Aerosols, Climate Assessment Report Faults. Bookmark the permalink.

4 Responses to Aerosols from Moderate Volcanos Now Blamed for Global Warming Hiatus

  1. FergalR says:

    Mr Tisdale – many thanks for your hard work on these matters.

    About a year ago many poor delusionals were blaming the warming hiatus on increased SO2 (though they were blaming Asian industry at the time). They were citing a graph from Vernier et al 2011 ( which they claimed showed a ginormous increase in reflective aerosols since 2000. Sadly the graph had a logarithmic scale and when compared to the forcing that GISS uses they’re practically identical since 2000:

    I may well be true that “the optical depth of the stratospheric aerosol layer between 20 and 30 km has increased 4–10% per year since 2000”, but it has increased from pretty much zero to pretty much zero.

  2. Bob Tisdale says:

    Thanks for putting it in perspective, FergalR. Please consider leaving a similar comment on the cross post at WUWT:

  3. Green Sand says:

    Bob, you may find this of interest, apologies if you have seen it.

    “Greg Goodman: Lunar-solar influence on Sea Surface Temperature”

    Some interesting info in the comments:-

  4. Pingback: Weekly Climate and Energy News Roundup | Watts Up With That?

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