There is a relationship between volcanic eruption and the climate of a place. After the eruption, the poisonous sulphur dioxide which is emitted out as a volcanic product, reacts and get oxidized to form sulphate aerosols in the stratosphere, hence affecting the climate adversely (Forster 2007). Volcanic ashes and particles having diameter larger than 2 um also affects the atmosphere. According to Ramaswamy (1996), ozone depletion results when the volcanic aerosols react with the balanced chemistry in the stratosphere. Mid and high latitudes volcanic eruptions create drastic climatic changes. The aerosols here retain over the hemisphere and cause climate to change. For example, the eruption of Laki volcano in Iceland in June was followed by ‘an exceptionally cold’ winter in 1783-84 (Thordason & Self 2003). The Millennium experiment has been used to study the climatic effects after volcanic eruptions in the mid and high latitudinal regions of the northern hemisphere with the coagulation of earth system model (Jungclaus et al, 2010). Jungclaus (2010) mentioned the use of COSMOS network which consisted of four models. The atmospheric general circulation model known as ECHAM5, the general circulation model known as MPI-OM, the ocean biogeochemistry model known as HAMMOC and lastly the land use and vegetation model JSBACH.
External natural forcing of the volcano, are based on observations, data and other references. The solar forcing depends on the tree ring and the ice core proxy reconstructions and also on the orbital forcing. Volcanic forcing is represented by varying the AOD at 0.55 um and the effective radius with a 10 days’ time resolution particularly for four latitudes: 30-90 degree north and south and 0-30 degree north and south latitudes. The volcanic AODs are based on a reconstruction. They used the data from 13 Greenland and Antarctic ice cores as the main source of data and spot data from the other sources. The effective radius growth and decay depends on the observations after the eruption happens. The temporal variation of the short wave radiation anomalies are based on changes in AOD, the solar zenith angle, the top surface of the atmosphere insolation and the surface albedo. Firstly, the aerosol radiative forcing becomes stronger with increasing AOD and secondly, the radiative forcing gets reduced in winter because the northern hemisphere receives less insolation than in summer. The AOD between 30 and 90 degree is horizontally uniform but in high latitudes, it is not uniform but peaks in summer. The temperature anomalies are similar to that of short wave radiation anomalies. The effects on the hemispheric scale are comparable with the internal variability of the model’s climate.
After evaluating the internal climate variability from a 1201 year simulation with the same model without external forcing, the result was that the standard deviation of northern hemisphere annual mean temperature was 0.24 K and the corresponding standard deviation for 2 years being 0.19 K. Anomalies are statistically significant at 90% level of large parts of continental and Arctic areas. Due to large heat capacity, the changes of the sea are small. After July, the largest anomalies start during autumn. The spatial distribution is similar to that in summer after January eruptions with anomalies smaller than 0.8 K. The distribution after the July eruption shows cooling over the Arctic sea. This is due to increased amount of sea ice during the autumn brought about by the cooling. September eruption caused the largest local anomalies in northeast Siberia, larger than 1.2 K and again above the continents and the Arctic Sea. In short, the volcanic eruptions in the Northern hemisphere in mid and high latitudes cause cooling over the continents and the northern ice sea as large as to 1 K. Internal and eruption induced climate variability sometimes causes slight warming in some regions.
The precipitation is also altered after a volcanic eruption. The precipitation anomalies tend to be negative after eruptions but a lot of variability exists. For example, after the January eruptions, the largest anomalies occur in September, December followed by next January and May. As earlier mentioned after an eruption, precipitation anomalies tend to be usually negative but only few of the mean monthly anomalies are statistically significant. A t-test was conducted considering the 21 months following the eruptions of January, July and September, the mean precipitation anomaly is 90% statistically significant. Hence, negative precipitation anomaly is significant. The result of the t-test shows larger variability in precipitation due to internal climate variability and other external factors.
The atmospheric carbon dioxide concentration anomalies are small after the eruptions around -0.0018 and 0.0043 kg per square meter compared to the mean burden of 4.3 kg per square meter. After the eruptions, anomalies are typically negative. In January and July eruptions, there are small positive anomalies during the summer and then larger positive anomalies in the following summer while for the September eruptions, no such increase is observed. The soil respiration and net primary production anomalies contributes to negative carbon dioxide burden while a slight reduction in the net primary production creates positive anomalies for January and July.
Summarising the paper, we have studied the change in climate in the mid and the high latitudes and also the anomalies associated with each climatic factor: temperature, precipitation, solar radiation, carbon dioxide burden etc and how the volcanic eruption affects these factors. The effects of eruption on temperature showed an average maximum temperature was -0.19 K and the average anomaly in the 21 months was -0.095 K following the eruptions. The average maximum anomaly in the hemisphere meant clear sky shortwave radiation was small. The effects of eruption on atmospheric carbon dioxide concentration were small. Precipitation anomalies also tend to be on a negative scale after the eruption.
Work Cited
Meronen, H. et al. ‘Climate Effects Of Northern Hemisphere Volcanic Eruptions In An Earth System Model’. Atmospheric Research 114-115 (2012): 107-118. Web.
