Next is the question of volcanic eruptions and their influence on climate. Read more: Climate explained: why we won't be heading into an ice age any time soon. What contribution have volcanic eruptions made to this variation in climate? As an example of a major influence, some scientists link mass extinctions to major volcanic eruption events. The most famous such association is that of the eruption of volcanoes that produced the Siberian Traps.
This is a large region of thick volcanic rock sequences, some 2. Rapid and voluminous volcanic eruptions around million years ago released sufficient quantities of sulphate aerosols and carbon dioxide to trigger short-duration volcanic winters, and long-duration climate warming, over a period of 10s of thousands of years. Most recently in geological terms , over the past million years ocean bottom waters have cooled, sea levels fallen and ice has advanced.
Within this period there have also been spells of a hotter Earth, most likely caused by natural rapid releases in greenhouse gases. Homo sapiens has evolved during the past few million years largely during an ice age when up to two-kilometre-thick ice sheets covered large areas of the northern continents and sea levels were over metres lower than today. This period ended 10, years ago when our modern interglacial warmer period began.
All of the geological and tectonic causes for this general longer-term Earth cooling are less well understood. Hypotheses include contributions from volcanoes and processes linked to the rise of the Himalayas and Tibet from 55 million years ago. Read more: Climate explained: why we need to cut emissions as well as prepare for impacts. Researchers have studied specific volcanic eruptions and climate change. Another important factor in whether a volcanic eruption influences climate is the amount of sulphur dioxide contained in the dust cloud.
And the quantities can be huge. Once in the stratosphere, fast-moving winds can quickly spread the ash cloud around the world, giving a local eruption a global impact. Schmidt says right now, the priority is to ensure aviation safety by monitoring and predicting how the ash cloud disperses.
Volcano eruptions can influence more than just temperature. Recent research suggests eruptions can affect the position of the Intertropical Convergence Zone ITCZ , a huge belt of low pressure that is the main source of rain for much of Africa. So in this case, the ITCZ could shift northwards, which would tend to promote rainfall in the Sahel but also enhance Atlantic hurricane activity. Steam and ash rise after the April 30th, eruption of the Calbuco volcano. It may be a while before the full impacts of the Calbuco eruption reveal themselves, says Dr Michael J.
But if it does turn out to be significant, scientists will have a unique research opportunity. Monitoring the impact of eruptions helps climate scientists refine models that project how the climate will respond to human-caused greenhouse gas emissions, explains McQuaid. Volcanic eruptions that reach the stratosphere also give scientists a glimpse of what geoengineering techniques could do, he adds:. Geoengineering is very controversial topic, with many unknown consequences, says McQuaid.
It caused what is believed to be the largest aerosol disturbance of the stratosphere in the twentieth century, though probably smaller than the disturbances from eruptions of Krakatau in and Tambora in Consequently, it was a standout in its climate impact and cooled the Earth's surface for three years following the eruption, by as much as 1. The large Laki fissure eruption in Iceland released a staggering amount more sulfur dioxide than Pinatubo approximately million ton vs.
Although the two eruptions were significantly different in length and style, the added atmospheric SO 2 caused regional cooling of Europe and North America by similar amounts for similar periods of time. Carbon dioxide CO 2 is a greenhouse gas and is the primary gas blamed for climate change.
While sulfur dioxide released in contemporary volcanic eruptions has occasionally caused detectable global cooling of the lower atmosphere, the carbon dioxide released in contemporary volcanic eruptions has never caused detectable global warming of the atmosphere.
In , human activities were responsible for a projected 35 billion metric tons gigatons of CO 2 emissions. All studies to date of global volcanic carbon dioxide emissions indicate that present-day subaerial and submarine volcanoes release less than a percent of the carbon dioxide released currently by human activities.
While it has been proposed that intense volcanic release of carbon dioxide in the deep geologic past did cause global warming, and possibly some mass extinctions, this is a topic of scientific debate at present. Published scientific estimates of the global CO 2 emission rate for all degassing subaerial on land and submarine volcanoes lie in a range from 0. The gigaton projected anthropogenic CO 2 emission for is about 80 to times larger than the respective maximum and minimum annual global volcanic CO 2 emission estimates.
There is no question that very large volcanic eruptions can inject significant amounts of carbon dioxide into the atmosphere. The eruption of Mount St. Helens vented approximately 10 million tons of CO 2 into the atmosphere in only 9 hours.
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