Rinjani: The volcano that started the Little Ice Age

We all know that huge volcanic eruptions can have a considerable effect on the climate. The 1883 eruption of Krakatau in 1883 resulted in a fall of average global temperatures by as much as 1.2 degrees Celsius in the year following the eruption[1]. Weather patterns continued to be chaotic for years and temperatures did not return to normal until 1888. In comparison to this, the eruption of Tambora in 1815 was of an even greater magnitude and resulted in the 'year without summer' because of the effect on North American and European weather. Crops failed and livestock died in much of the Northern Hemisphere, resulting in the worst famine of the 19th century.

Now we turn to Gunung Rinjani, a still very much active volcano on the Indonesian island of Lombok. On the top of the volcano is a 6 by 8.5 kilometer caldera, which is partially filled by a crater lake that is locally known as Anak Laut ('Child of the Sea') due its azure colour. Located in the lake is the ominously growing crater cone called Gunung Barujari (Finger Mountain). That crater within a crater grew during a spate of activity from 1994 to 1995. On 31 October 2015, Mount Rinjani started erupting again.

So, what happens if such a massive volcano erupts in earnest?

Rinjani's huge caldera is probably formed sometime in the 13th century. Based on radiocarbon dates on charcoal, tephra dispersal and historical records, the eruption can be dated to 'between May and October of 1257'[2]. This colossal eruption is now considered the likely source of high concentrations of sulfur found in widely dispersed ice core samples and may have been 'the most powerful volcanic blast since humans learned to write'. There is even a preserved manuscript, Babad Lombok, written in Old Javanese on palm leaves, which records a catastrophic eruption of Rinjani. The massive eruption may have triggered a prolonged episode of global cooling and failed harvests, called the ‘Little Ice Age’, a cold snap defined variously within the 14th–19th century range.

Estimates based on sulfate deposition suggest that it yielded the largest volcanic sulfur release to the stratosphere of the past 7,000 years. The eruption triggered worldwide atmospheric and climatic effects of this eruption. Scientists argue that the source of this long-sought eruption is the Samalas volcano, once a twin peak adjacent to the Rinjani volcano, but destroyed during the explosion.

[A 'minor' eruption in 1994]

According to the new study, the Little Ice Age began abruptly between 1275 and 1300 A.D., triggered by repeated, explosive volcanism and sustained by a self-perpetuating sea ice-ocean feedback in the North Atlantic Ocean[3].

PS: The 'minor' eruption in the second image has its origin in Gunung Barujari, the 'small' volcano in the center of the massive caldera/lake of Gunung Rinjani you see in the first image.

[Update August 11, 2016] An eruption at Rinjani on 1 August generated an ash plume that rose to an altitude of 9.8 kilometers. Lombok International Airport temporarily closed as a result of that ash plume. Later, the situation returned to 'normal' although the public should stay at least 1.5 km away from the volcano. 

[1] Gleckler et al: Volcanoes and climate: Krakatoa's signature persists in the ocean in Nature - 2006
[2] Lavigne et al: Source of the great A.D. 1257 mystery eruption unveiled, Samalas volcano, Rinjani Volcanic Complex, Indonesia in Proceedings of the National Academy of Sciences of the United States of America. – 2013. See here.
[2] Miller et al: Abrupt onset of the Little Ice Age triggered by volcanism and sustained by sea-ice/ocean feedbacks in Geophysical Letters – 2012