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Research: Volcanic Aerosols Contribute To The Pause

23.02.2014
23.02.2014 17:49 Age: 3 yrs

New research suggests that climate models may have overestimated global warming because they do not include the impact of aerosols from volcanic eruptions. The implication is that this may be a partial explanation of the so called global warming pause since volcanic materials dim the sun and cool the planet - partially offsetting the warming effect of greenhouse gases. We also include (below) the text of a news release issued by MIT.

Click to enlarge. Volcanoes eject material which forms aerosols in the stratosphere which makes the atmosphere more opaque, dims the sun, and cools the planet. The effect is thought to be contributing to the so called global warming pause. Image courtesy: MIT.

Click to enlarge. Behaviour of overlapping 10-year trends in the ‘ENSO removed’ near-global (82.5 N–70 S) TLT data. Least-squares linear trends were calculated over 120 months, with overlap by all but one month; that is, the first trend is over January 1979–December 1988, the second trend over February 1979–January 1989, and so on. The last trend is over January 2003–December 2012. Courtesy: Santer et al and Nature Geoscience.

Prof Piers Forster, Professor of Climate Change at the University of Leeds, said: "This is a good paper and confirms the Intergovernmental Panel for Climate Change position that recent volcanoes contribute to the slowdown but cannot be the only cause. Volcanoes give us only a temporary respite from the relentless warming pressure of continued increases in CO2."

 

 

News release

Here is the text of a news release issued by MIT regarding this research:

 

 

 

 

by Alli Gold Roberts, MIT Joint Program on the Science and Policy of Global Change




The researchers verified the cooling phenomenon by performing 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 both tropospheric temperature and sunlight reflected by the particles off the top of the atmosphere. 






The research was supported by the U.S. Department of Energy.

News release ends

 

Abstract

Despite continued growth in atmospheric levels of greenhouse gases, global mean surface and tropospheric temperatures have shown slower warming since 1998 than previously. Possible explanations for the slow-down include internal climate variability, external cooling influences and observational errors. Several recent modelling studies have examined the contribution of early twenty-first-century volcanic eruptions to the muted surface warming. Here we present a detailed analysis of the impact of recent volcanic forcing on tropospheric temperature, based on observations as well as climate model simulations. We identify statistically significant correlations between observations of stratospheric aerosol optical depth and satellite-based estimates of both tropospheric temperature and short-wave fluxes at the top of the atmosphere. We show that climate model simulations without the eects of early twenty-first-century volcanic eruptions overestimate the tropospheric warming observed since 1998. In two simulations with more realistic volcanic influences following the 1991 Pinatubo eruption, differences between simulated and observed tropospheric temperature trends over the period 1998 to 2012 are up to 15% smaller, with large uncertainties in the magnitude of the effect. To reduce these uncertainties, better observations of eruption-specific properties of volcanic aerosols are needed, as well as improved representation of these eruption-specific properties in climate model simulations.


Citation

 

Read the abstract and get the paper here.


Source

Nature press release and Nature Geoscience.

MIT press release here.

Notes

Headline change to better reflect story content 0700 24 February 2014.

This story was further updated to include the text of the MIT news release at 1030 24 February 2014.