Volcanic eruptions climate change

Volcanic eruptions cause changes in RF from 0.2 Wm 2 to 0.5 W m 2 (these values, however, are very conditional). To analyze the possible anthropogenic impacts on global climate, estimates of the sensitivity of the climate system to external forcings are very important. Hansen et al. (1998) assumed that a change in global mean SAT with a doubled C02 concentration should constitute 3 1°C. The unreliable character of RF estimates makes it worthwhile to use different scenarios of RF changes. Developments in this field can be exemplified by the work of Tett et al. (1999). 

Extreme climatic phenomena such as droughts, large shifts of seasonal temperatures, change of solar radiation due to the large-scale input of aerosols to the atmosphere (e.g., by volcanic eruptions or by the large-scale fires that took place in Iraq in connection with recent military operations). 

The DVI does not take into account the detailed nature of the process and is based on a fair amount of estimation it can be argued, for instance, that it is not the total amount of dust that matters, but rather the fraction that reaches the stratosphere, particularly as a sulfur compound, and how that content evolves in time also, it is not just the change in direct radiation that has an effect, but the redistribution, in the entire spectrum, of the direct and diffuse radiation, etc. The DVI is an approach to identify and relate the rdevant and measurable parameters it gives a useful insight by associating volcanic and climatic chronologies. In the words of the author this is about as far as one can go towards objectivity in the assessment of past eruptions . In this respect it reflects the state of knowledge on the problem in 1970. 

The Earth was gripped by continuing climatic mayhem as changes in its orbit began inexorably to push down the world s thermostat. Then to add to these woes, about 74,000 years ago. Mount Toba on the island of Sumatra exploded in the largest volcanic eruption of the past 450 million years. The blast... 

The observed trends in the NAM towards higher indices may have resulted from human-induced changes in the temperature structure of the lower stratosphere in response to greenhouse gas emissions and ozone depletion (Shindell et al., 2001). The radiative effects of solar activity and of volcanic eruptions may also have produced NAM- like signatures detectable at the Earth s surface. The response of the Earth system to climate forcing may therefore involve changes in particular dynamical modes, and hence the human influence on climate at the Earth surface may occur in part by way of the stratosphere. 

Changes in concentrations of stratospheric aerosols, caused by intense, episodic volcanic eruptions, are natural climatic experiments. Because of the 1 to 2 year residence... 

This includes also catastrophic events such as volcanic eruptions and the impaet of celestial bodies. It is beyond the focus of this book to describe the physics of sueh alterations. However, with an understanding of the chemical evolution of the eli-mate system (Chapter 2), it is evident that different chronological processes are superposed and that the different causes are interlinked in the sense of climatic feedbacks which make it very difficult to quantify climate changes and variations. Temperature and precipitation, as the most important climatic factors, are interrelated, but they are also interrelated with atmospheric composition and surface characteristics which again are interrelated. 

Volcanism has long been implicated as a possible cause of weather and elimate variations Benjamin Franklin and William Jackson Humphrey were pioneers in their association of volcanic eruptions with climate change. Franklin (1784) put forward a theory linking volcanic dust to climatic change ... 

Nevertheless, the ice sheets of Antarctica and Greenland are archives that contain a recording of global climate change, volcanic eruptions and explosive impacts of exterrestrial objects. The ice also contains evidence of the contamination of the atmosphere by the human population of the Earth. 

Forcing factors Influences that force the climate system, such as natural (solar output changes and volcanic eruptions) and human factors (greenhouse gases, land-use changes). 

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