Climate & volcanoes

Stratospheric injection of sulfur aerosols

global cooling for 1-3 years

1815 Tambora

weak precursor explosions, climatic eruption of plume and fountaining

Global phenomena of tambora

colored sunsets & twilights in london, persistent dry fog, high stratospheric aerosol veil, year without summer

Temperature anomalies 

Europe: coldest summer based on tree ring records, short growing season, more days than normal are way colder than normal 

sulfate concentrations in ice cores

spikes prior to tambora which points to an equiatorial eruption > explains why global temperatures were lower than usual before

Global climate impact (hemispheres)

southern hemisphere showed weaker signs > large oceans and land distribution prevents major anamolies

Why can winters become warmer after large volcanic eruptions that inject sulphur dioxide (SO₂) into the stratosphere?

Volcanos release SO2 into the stratosphere
these aerosols absorb solar radiation warming the stratosphere
this increases the latitudinal thermal gradient altering atmospheric circulation
although surface cooling occurs initially (due to sunlight reflection), the altered circulation can lead to warmer winters especially in the northern hemisphere

Samalas Volcanic eruption indicators

sulfur in ice cores 2x tambora, but less evidence of global climate change 

petrological based

2-3x more SO2 than humans/year

tree ring data

extreme average surface cooling in 1259 > persistent dust veil over europe ‘dark year’
**warmer than average in northern canada (doesn’t make sense)
Not hemisphere-wide cooling

linear thinking 

the bigger the eruption, the bigger the effect (NOT TRUE)!

Global climate

(1) tambora and Samalas, global aerosol viel > cooling! 

(2) normal total volcanic CO2 release is about 100x less than anthropogenic > little greenhouse effect 

(3) atm CO2 reduced 
Fe fertilization of oceans & phytoplankton blooms > drawdown biological pump
Diffuse sunlight that promotes photosynthesis & forest growth 

(4) stratopsheric volcanic aerosols act as catalysts for reactions between chlorine, nitrate, and chlorine gas to release chlorine > destroy ozone layer

(5) multiple large sulfer-rich eruptions within years or decades > additive impact, proposed for little ice age

Risks

Risk is a social construct, the hazard has not changed, but the risk has increased

(1) population growth 
(2) complex food, water & shelter systems (no-longer sufficient)
(3) just-in-time supply chain > many things are not locally stored

(4) technological dependency

Food and agriculture 

Cities feed humans > energy and transport dependent 

Thick ash deposition in major cities 

Roads, railways and airways closed 

Agriculture is a global interprise > vulnerable to volcanic disruptions everywhere