A volcano erupting as Krakatoa did in 1883 will change climate dramatically for years to come.
Global climate[edit]
In the year following the 1883 Krakatoa eruption, average Northern Hemisphere summer temperatures fell by as much as 1.2 °C (2.2 °F).[12] Weather patterns continued to be chaotic for years, and temperatures did not return to normal until 1888.[12] The record rainfall that hit Southern California during the water year from July 1883 to June 1884 – Los Angeles received 38.18 inches (969.8 mm) and San Diego 25.97 inches (659.6 mm)[13] – has been attributed to the Krakatoa eruption.[14] There was no El Niño during that period as is normal when heavy rain occurs in Southern California,[15] but many scientists doubt that there was a causal relationship.[16]
The Krakatoa eruption injected an unusually large amount of sulfur dioxide (SO2) gas high into the stratosphere, which was subsequently transported by high-level winds all over the planet. This led to a global increase in sulfuric acid (H2SO4) concentration in high-level cirrus clouds. The resulting increase in cloud reflectivity (or albedo) reflected more incoming light from the sun than usual, and cooled the entire planet until the suspended sulfur fell to the ground as acid precipitation.[17]
Global optical effects[edit]
1888 paintings, showcasing the optical effects of the eruption on the sky over time
The 1883 Krakatoa eruption darkened the sky worldwide for years afterwards and produced spectacular sunsets throughout the world for many months. British artist William Ashcroft made thousands of colour sketches of the red sunsets halfway around the world from Krakatoa in the years after the eruption. The ash caused "such vivid red sunsets that fire engines were called out in New York, Poughkeepsie, and New Haven to quench the apparent conflagration."[18] This eruption also produced a Bishop's Ring around the sun by day, and a volcanic purple light at twilight.
In 2004, an astronomer proposed the idea that the red sky shown in Edvard Munch's famous 1893 painting The Scream is also an accurate depiction of the sky over Norway after the eruption.[19]
Weather watchers of the time tracked and mapped the effects on the sky. They labeled the phenomenon the "equatorial smoke stream".[20] This was the first identification of what is known today as the jet stream.[21]
For several years following the eruption, it was reported that the moon appeared to be blue and sometimes green. This was because some of the ash clouds were filled with particles about 1 µm wide – the right size to strongly scatter red light, while allowing other colors to pass. White moonbeams shining through the clouds emerged blue, and sometimes green. People also saw lavender suns and, for the first time, recorded noctilucent clouds.[18]
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1883 eruption of Krakatoa - Wikipedia