In this entry I am presenting this data on oil spills in our world’s oceans. Over the past 4 decades – the time for which we have data – oil spills decreased dramatically. Although oil spills also happen on land, marine oil spills are considered more serious as the spilled oil is less containable. For this reason I am looking at marine oil spills only.
# Empirical View
# Decreasing Number of Oil Spills
The dataset used below covers more than four decades over which time the incidence of large oil spills greatly decreased. The 450 large (>700 tonnes) oil spills are distributed as follows:
|Decade||Share of total oil spills||# of oil spills||Average oil spills per year|
Number of medium sized (7-700 tonnes) and large spills (> 700 tonnes) caused by tankers, 1970-20122Download this graph as a static image
Similarly to the large oil spills, medium sized oil spills (7-700 tonnes) are also decreasing.
Number of medium sized (7-700 tonnes) and large (>700 tonnes) spills caused by tankers per decade, 1970-20123
# Decreasing Quantities of Oil Spilled
ITOPF estimated that between 1970 and 2012 approximately 5.75 million tonnes of oil were lost as a result of tanker incidents. As single large incidents can be responsible for a huge share of all the oil spilt in a given year, it is advisable to look at trends or decade averages. Over these 43 years, the annual quantity of oil spilled decreased hugely. ITOPF notes that an ‘amount greater than the total quantity of oil spilt in the decade 2000 to 2009 was spilt in several single years in earlier decades’. 2012 saw the lowest oil spillage on record so far: 1000 tonnes were spilled. The development can be seen in the following two figures.
Oil spilled per decade as a percentage of the total spilled, 1970-2009 – ITOPF4
Quantities of oil spilt > 7 tonnes by tankers, 1970-2012 – ITOPF 5
# Increasing Seaborne Oil Trade
The change of seaborne oil trade can be inferred from the following figure. Since the mid-1980s, seaborne oil trade has been increasing while the number of oil spills is decreasing. This makes clear that the decrease in oil spills is not due to a decrease in oil trade. Information on the causes of spills can be found here (under ‘Causes of Spills’).
# Seaborne oil trade and number of tanker spills > 7 tonnes, 1970-2011 – ITOPF6
# Oil Spills Unrelated to Tankers
According to the ITOPF dataset, the largest oil spill caused by a tanker was caused by the SS Atlantic Empress, which sank close to Trinidad and Tobago in 1979. Wikipedia lists five oil spills which were not caused by tankers and were larger than this. The biggest oil spill in history was the Lakeview Gusher (1910-11 in California), the second was the Gulf War oil spill (1991), the 3rd biggest was the Deepwater Horizon (2010), 4th was Ixtoc I oil spill in Mexico (1979-1980) and 5th was a long-lasting spill in the Niger Delta between 1976 and 1996. (The source is Wikipedia here)
# Data Sources
The International Tanker Owners Pollution Federation (ITOPF) maintains a database on oil spills caused by tankers, combined carriers and barges since 1970. The data covers the entire planet. The database can be found here. As of 2013 10,000 incidents are recorded. For all of these the ITOPF data base records the type of oil spilled, the spill amount, the cause and location of the incident and the vessel involved. The size of a spillage is grouped into three categories: less than 7 tonnes, 7-700 tonnes, and more than 700 tonnes of oil spilled. The majority of incidents belong to the smallest category of spillages. Nowadays oil spills can be detected by computer systems on the basis of satellite images. For the past, data is taken from other sources: Data on smaller spills are taken from the vessel owners and their insurers. For the larger spills the majority of information is taken from published sources of the shipping press.