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The role of volcanic eruptions
in climate change
Wyss W.-S. YimDepartment of Earth Sciences, The University of Hong Kong
* This presentation is a contribution to UNESCO’s International Year of Planet Earth
2007-2009 (http://www.yearofplanetearth.org).
Why volcanoes?Why volcanoes?
Major volcanic eruptions have long been
known to cause climate change e.g. lowering of global temperatures.
Main objectiveTo examine the impact of three ‘large’
volcanic eruptions occurring over the past 50 years on temperature and precipitation distribution in Hong Kong.
Volcanic explosivity index (VEI)Volcanic explosivity index (VEI)
Three major eruptions in the pastThree major eruptions in the past(Francis 1993)(Francis 1993)
_________________________________________________________________________________
Eruption/ VEI* Magma vol. Eruption column H2SO4 aerosols Temp.year (km3) height (km) (kg) drop (oC)
_________________________________________________________________________________
Tambora 7 > 50 > 40 2 x 1011 0.4-0.71815
Krakatoa 6 > 10 > 40 5 x 1010 0.31883
St. Helens 5 0.35 > 22 3 x 108 0-0.11980
_________________________________________________________________________________* Volcano explosivity index.
Yellowstone supervolcano ?VEI 7Yellowstone supervolcano ?VEI 7--88
VEI 5
Role in climate changeRole in climate change- Volcanic clouds reduce incoming solar
radiation
- Plumes interfere with normal wind circulation/jet streams
- Aerosols (particulates & gases) may provide condensation nucleus for precipitation
Outcomes(1) Temperature drop/cooling
(2) Extremes in precipitation
↑The Model
Thermal plume
Warm airstoresmore
Cool airstoresless
Eruptionchangesnormalaircirculation
→ ← Coolair
moremoisture
lessmoisture
El Chichón, Mexico 1982
Wind belts of the worldWind belts of the world
Changes innormalcirculation
Offshore wind- drier
circulationwould resultin precipitationvarablity
Onshore wind- wetter
Possible climatic impacts of major eruptionsPossible climatic impacts of major eruptions
(1) Initially increase the temperature of the lower stratosphere followed by cooling of the troposphere.
(2) Volcanic clouds obstruct the incoming solar radiation causing the Earth’s surface temperature to decrease.
(3) The thermal plumes interfere with the Earth’s air circulation changing the water Earth’s air circulation changing the water balance in the atmosphere causing extremes in precipitation regionally.
(4) Particulates and gases in the stratosphere form condensation nucleus.
(5) The sulphur dioxide released may lead to acid precipitation causing vegetation damage.
The three volcanic eruptions selected for the The three volcanic eruptions selected for the present studypresent study
●●●● HK
+ AgungIndonesia 2/1963
+ El ChichónMexico 3/1982
●●●● HK
+ PinatuboPhilippines 6/1991
Latitude, first eruption date, volume of materials Latitude, first eruption date, volume of materials erupted and annual precipitation at the Hong Kong erupted and annual precipitation at the Hong Kong Station during the 1963 Agung, 1982 El ChichStation during the 1963 Agung, 1982 El Chichón and ón and 1991 Pinatubo eruptions1991 Pinatubo eruptions_______________________________________________________________________
Volcano Latitude First eruption Volume of materials Precipitation Comment*
date erupted (mm)
_________________________________________________________________________________
Agung, 8oS February 18, ~1 km3 (Rampino and 901.1 Driest year
Indonesia 1963 Self, 1982)
El Chichón, 17oN March 28, ~0.6 km3 (Rampino and 3247.5 2nd wettest
Mexico 1982 Self, 1984) year
Pinatubo, 15oN June 15, ~5 km3 (Self et al., 1999) 1639.1 10th driest
Philippines 1991 year
_________________________________________________________________________________
* Since 1884.
Temperature/precipitation record used
+ Hong Kong Station of theHong Kong Observatory(1884 to present exceptfor 2nd World War break)
Source: Geocarto
February 18, 1963 Agung eruption, IndonesiaWater rationing in Hong Kong with 4 hours supply in 4 days? Trigger for the construction of the High Island Water Scheme
June 15,1991 Pinatubo eruption, Philippines
Visible IRVisible IR--wavelength images spanning 3 h from 1340 to 1640 local time on June 15, 1991wavelength images spanning 3 h from 1340 to 1640 local time on June 15, 1991
ThermalThermal--IR images spanning 3 h from 1340 to 1640 local time on June 15, 1991IR images spanning 3 h from 1340 to 1640 local time on June 15, 1991
Temperature retrieved from weather satellite images of the Temperature retrieved from weather satellite images of the relatively warm ash plume blowing westward off the overshooting relatively warm ash plume blowing westward off the overshooting top of the Pinatubo umbrella cloud.top of the Pinatubo umbrella cloud.
Spread of the Pinatubo volcanic cloud on the dates indicated and the transition from ash-laiden eruption cloud to SO2-dominated stratospheric cloud mapped by TOMS satellite.
Space shuttle photograph of the Earth over South America taken Space shuttle photograph of the Earth over South America taken on August 8, 1991, showing double layer of Pinatubo aerosol on August 8, 1991, showing double layer of Pinatubo aerosol cloud (dark streaks) above high cumulonimbuscloud (dark streaks) above high cumulonimbus
+ Pinatubo
+ Hong Kong
Wind shift topredominantlyoffshore through strengthening ofITCZ
ReasonfordroughtduringAgungand + Pinatubo
+ Agung
andPinatuboeruptions
▬▬▬▬
1000 kms
What makes droughts worse in HK?What makes droughts worse in HK?
Two examples:
1962 Rainfall at Hong Kong Station 1741.0 mm (79.7 % of average)
1963 Rainfall at Hong Kong Station 901.1 mm (41.3 % of average)
Nuclear testing –
31/10/1961 USSR explodes the world’s largest nuclear bomb
1967 Rainfall at Hong Kong Station 1570.6 mm (71.9 % of average)
Nuclear testing –
24/9/1966 France explodes atomic bomb at Mururoa Atoll
March 28, 1982 El ChichMarch 28, 1982 El Chichón eruption, ón eruption, MexicoMexico
Before AfterI
(Rampino & Self 1984)
El ChichEl Chichón 1982 eruptionón 1982 eruption
Location - Latitude17.33oN
Longitude 93.2oW
Timing - 1st eruption 11.32 pm March 28
2nd eruption 7.35 pm April 3
3rd eruption 5.22 am April 43rd eruption 5.22 am April 4
Tephra - ~0.6 km3 of trachyandesite
Aerosol - 3.3 million tons of SO2
Impact - ? trigger of the intense El Niño of 1982-3 (2nd strongest on record)
Crustalsedimentsand rocksandsubductingoceancrustare both richin sulphur-bearingminerals
Cross-section of Earth from Rampino & Self (1984)
minerals
Westerly driftof volcaniccloud detected by satellites (Rampino and Self 1984)
Observations of the El ChichObservations of the El Chichón ón eruption eruption cloud (Francis 1993)cloud (Francis 1993)
Average velocity - 20 m / second
Westward drift - Circled the world on April 26, 1982
Cloud dispersion - Most of the cloud remained south of 30oN
for more than 6 months after the eruption,
blocked by atmospheric circulation cells
Aerosol particles - average diameters 3 to 6 microns
85% glass shards coated with sulphuric
acid
Monthly rainfall at the Hong Kong Station in 1982Monthly rainfall at the Hong Kong Station in 1982
____________________________________
Month Rainfall (mm)____________________________________
January 16.0February 23.1March 30.6April 310.0May 767.4 1st peak
Total 3247.5 mmAnnual average 2214.3 mm146% above average
Normal for April 139.4 mm- 222% above normal- 7th wettest on record
May 767.4 1st peakJune 205.9July 296.2 August 872.0 2nd peakSeptember 466.8October 163.7November 95.8December trace____________________________________
- 7 wettest on record- relative humidity 5th lowest on record
Normal for May 298.1 mm- 257% above normal- 4th wettest on record- worst landslides since 1976
Flooding of Kwai Chung Road (trough effect) on August 17, 1982
Mean annual temperature recorded at the Hong Kong Mean annual temperature recorded at the Hong Kong Station during, 1Station during, 1--year after and 2year after and 2--year after the year after the eruption of Agung, El Chicheruption of Agung, El Chichón and Pinatuboón and Pinatubo
_________________________________________________________________________________
Volcano Month and Mean annual Mean annual Difference Mean annual Difference
year of temperature temperature from year temperature from year
eruption during year after 1 year of eruption after 2 years of eruption
_________________________________________________________________________________
Agung 2/1963 23.3 22.9 -0.4 23.1 -0.2
El Chichón 3/1982 22.9 23.0 +0.1 22.5 -0.4
Pinatubo 6/1991 23.5 22.8 -0.7 23.1 -0.4
_________________________________________________________________________________
Main conclusionsMain conclusions(1) Volcanic eruptions have been found to lower the
Earth’s surface temperature.(2) Volcanic eruptions have a role in monsoonal
variability causing extremely dry and wet years.(3) Because volcanic eruptions are natural, it is
dangerous to attribute the occurrence of all floods and droughts to global climate change through the production of man-made greenhouse gases without detailed investigations.
(4) Volcanic eruptions are mega-scale equivalents of power stations/urban heat islands of mega-cities/bush fires. All are thermal plumes differing in time and space.
(5) Nuclear testing may also have a role similar to volcanic eruptions.
(6) The study of volcanic eruptions should be helpful to assist water/land resource management.
