Climate and volcanoes (2)

Example of an eruption & Characteristics

1815 Tambora
Phreatomagmatic eruption
40 km plume and fountaining
Incandescent flows
Darkness & cold for 2 days
tsunami & pyroclastic flow

Global phenomena observed by Tambora

colored sunsets
persistent dry fog
high stratospheric sulfate aerosol veil
year without summer

Tambora eruption & eruope

coldest summer based on tree ring studies > led to short growing seasons

temperature anamolies of tambora 

effects were not felt the same everywhere, more days than normal are way colder than normal

optical depths?

gets worse within the first half year after the eruption (oppenheimer 2003)

sulfate concentrations in ice cores

spikes prior to tambora, point to equatorial eruption
may explain why global temperatures were lower than usual before the tambora eruption

Southern hemisphere?

showed weaker signs of climate effects because of large oceans and land distribution (prevents major anomalies)

why did the winter after become normal?

because the cooling at the surface is accompanied by heating in the stratosphere 

What happens when you put more sulphur dioxide into the stratosphere

you warm up the stratosphere and that increases the latitude thermal gradient

what was warming also caused by?

north atlantic oscillation

Context of tambora eruptuon

largest known event in the past two millenia 
similar sized eruptions about 1 per 1000 yr 

Samalas volcanic eruption

sulfur in ice cores 2x tambora, but less evidence of global climate change
petrological based, released 2-3x SO2 than humans per year

effects of the salmas eruption in europe

cold, incadessant rainfall & high cloudiness > crop failures
persisten dust veil ‘dark year’

what does tree ring data show 

extreme average surface cooling in 1259

What did & did not add up about the Samalas eruption?

Wester europe strong cooling, warmer-than average conditions over alaska and northern canada > not hemisphere wide cooling ( Guiliet S et al., 2017)

linear thinking

the bigger the eruption, the bigger the effect (not true)

Overall global climate impacts

(1) global aerosol veil > cooling/

(2) total CO2 release is less than anthropogenic

atmospheric CO2 reduced

Fe fertilization of oceans & phytoplankton blooms > slowed down biological pump
diffuse sunlight that promotes photosynthesis

stratospheric volcanic aerosols act as

catalysts for reactions between chlorine, nitrate, and chlorine gas > destroys ozon layer

what can multiple sulfer-rich euptions within years or decades cause

additive impact, possible little ice age

Proximal and direct hazards

pyroclastic flow, thick pumice and ash, disruption of air traffic

hazard has not changed, but the risk has increased

population growth
no longer self-sufficient
just in time supply chains
technological dependency

food and agriculture

thick ash in major cities impacts energy and transport (delays in electrical power grids)
agriculture is global (vulnerable to volcanic disruptions everywhere)

VEI eruptions since 1970

loss of 70% of wild animal biomass
atmospheric CO2 has increased
ecological footprint is increasing