Climate Science Glossary

Term Lookup

Enter a term in the search box to find its definition.


Use the controls in the far right panel to increase or decrease the number of terms automatically displayed (or to completely turn that feature off).

Term Lookup


All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

Home Arguments Software Resources Comments The Consensus Project Translations About Support

Twitter Facebook YouTube Pinterest MeWe

RSS Posts RSS Comments Email Subscribe

Climate's changed before
It's the sun
It's not bad
There is no consensus
It's cooling
Models are unreliable
Temp record is unreliable
Animals and plants can adapt
It hasn't warmed since 1998
Antarctica is gaining ice
View All Arguments...

New? Register here
Forgot your password?

Latest Posts


How do volcanoes drive climate?

What the science says...

A drop of volcanic activity in the early 20th century may have had a warming effect. However, volcanoes have had very little impact on the last 40 years of global warming.

Climate Myth...

A drop in volcanic activity caused warming

"There is no question the Earth has been warming; it is coming out of the 'Little Ice Age'. However, there is no credible evidence that it is due to mankind and carbon dioxide. We've been coming out of a Little Ice Age for 300 years. We have not been making very much carbon dioxide for 300 years. It's been warming up for a long time. The Little Ice Age was driven by volcanic activity. That settled down, so it is getting warmer" (Reid Bryson)

Volcanoes emit sulfate aerosols which reflect incoming sunlight, cooling the planet. A large volcanic eruption such as the Pinatubo eruption in 1991 can have a global cooling effect of 0.1°–0.3°C for several years (Robock 1994, Zielinski 2000).

However, mega-eruptions or a series of eruptions can have a cooling effect that take decades to wear off, giving a perceived warming effect. Zielinski 2000 studies past volcanoes, particularly over the past few centuries:

Figure 1: Perturbations in the mean annual optical depth from volcanic eruptions

Zielinksi concluded "the lack of any climatically effective volcanism in the period 1920s to early 1950s undoubtedly contributed to the overall warm conditions during those decades." (Zielinski 2000).

This is confirmed by Hegerl 2003 who found:

"early 20th century warming is attributed to a composite of greenhouse warming, an uncertain contribution from solar forcing, and a recovery from a previous period of heavy volcanism"

Similarly, Bertrand 1999 found:

"the lack of volcanism during the period 1925-1960 could account, at least partly, for the observed warming trend in this period". Bertrand was investigating the effect of solar and volcanic influence on climate and concluded "these are clearly not sufficient to explain the observed 20th century warming and more specifically the warming trend which started at the beginning of the 1970s".

In short, a lack of volcanic activity had some part in temperature rise over the first half of the 20th century. However, it has played little part in the modern global warming trend that began in the 1970s.  Foster and Rahmstorf (2011) used a multiple linear regression approach to filter out the effects of volcanic and solar activity, and the El Niño Southern Oscillation (ENSO).  They found that volcanic activity, as measured by aerosol optical thickness data (AOD) has only caused between 0.02 and 0.04°C per decade warming from 1979 through 2010 (Table 1, Figure 2), or about 0.06 to 0.12°C warming of the surface and lower troposphere, repsectively, since 1979 (out of approximately 0.5°C observed surface warming).

Table 1: Trends in  °C/decade of the signal components due to MEI, AOD and TSI in the regression of global temperature, for each of the five temperature records from 1979 to 2010.

table 3

Figure 7

Figure 2: Influence of exogenous factors on global temperature for GISS (blue) and RSS data (red). (a) MEI; (b) AOD; (c) TSI.

Like Foster and Rahmstorf, Lean and Rind (2008) performed a multiple linear regression on the temperature data, and found that although volcanic activity can account for about 10% of the observed global warming from 1979 to 2005, between 1889 and 2006 volcanic activity had a small net cooling effect on global temperatures.  Thus volcanoes have not caused the long-term global warming over the past century, and can explain only a small fraction of the warming over the past 25 years.

A number of studies have used a variety of statistical and physical approaches to determine the contribution of greenhouse gases and other effects to the observed global warming, like Foster & Rahmstorf and Lean & Rind.  And like those studies, they find that volcanoes have had a relatively small contribution to global warming, and in fact, likely have had a net cooling effect over the past 50-65 years (Figure 3).

volcanic attribution

Figure 3: Volcanic contribution to global warming according to various peer-reviewed attribution studies

Last updated on 4 November 2016 by dana1981. View Archives

Printable Version  |  Offline PDF Version  |  Link to this page

Argument Feedback

Please use this form to let us know about suggested updates to this rebuttal.

Related Arguments


Comments 1 to 1:

  1. Henry Justice, Perhaps this is a better thread to raise your volcano questions. (I could not find an ice and volcano thread). I suggest that you calculate how much energy a volcano emits and compare that to how much energy it takes to melt a gigaton of ice. You will find that even if there is a volcano in the middle of an Antarctic glacier the melting it causes is not significant. The energy imbalance in the Arctic is equal to hundreds of unknown volcanoes (would so many volcanoes cause seismic activity?). In keeping with your posts I have provided no references, that is your responsibility.

Post a Comment

Political, off-topic or ad hominem comments will be deleted. Comments Policy...

You need to be logged in to post a comment. Login via the left margin or if you're new, register here.

Link to this page

The Consensus Project Website


(free to republish)

© Copyright 2021 John Cook
Home | Links | Translations | About Us | Privacy | Contact Us