Find out about our iPhone app...
Support Skeptical Science:    Latest Posts
|
 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) What the science says...A drop of volcanic activity in the early 20th century may have had a warming effect. However, volcanoes have had no warming effect in the last 40 years of global warming. If anything, they've imposed a slight cooling effect. What about the 'coming out of an ice age' theory? 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:
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 that "early 20th century Similarly, Bertrand 1999 found that "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 had little to no part in the modern global warming trend that began in the 1970's. On the contrary, relatively frequent volcanic activity in the late 20th century may have masked some of the warming caused by CO2. Printable Version | Link to this page
Related ArgumentsThere have been no comments posted yet. Post a CommentPolitical, 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. |
| © Copyright 2010 John Cook | Links | Translations |
 |
|
The skeptic argument...