An analysis of satellite data collected during 1993-2014 has revealed a more accurate picture of global sea level rise, showing that it is happening much faster than previously thought.
Bora Bora, the Society Islands of French Polynesia. Image credit: Maria Michelle.
“This information is vital as communities around the world plan and respond to our changing climate,” said Dr Christopher Watson of the University of Tasmania, Australia, lead author on the study published in the journal Nature Climate Change.
“Previously, it was clear that the rate of rise over the past 20 years was roughly double the rate determined over the past century – what was curious was that the rate appeared slower in the last decade relative to the one before.”
“That slowing has puzzled scientists because it coincides with an increase in water entering our oceans from Greenland and West Antarctica.”
According to the analysis, seas have risen faster since 1993 relative to the slower rate over previous decades.
After allowing for land motion at the tide gauges, the first six years of the satellite record was found to marginally overestimate the sea-level trend.
The team’s revised estimate of global mean sea level rise for the satellite era (1993 to mid-2014) is approximately 2.6-2.9 mm per year, slightly less than the previous estimate of 3.2 mm per year.
The revised record suggests the rate of rise has actually increased over the satellite era (within the period 1993 to mid-2014).
However, sea level varies from year to year as water is exchanged between the land and sea in events like the Australian floods in 2011 and as a result, the observed increase in the rate of rise is not yet statistically significant.
“Unlike the previous slowing, an estimate of acceleration is striking in that it is consistent with the projections of future sea level published by the Intergovernmental Panel on Climate Change,” Dr Watson said.
“Projections are for up to a 98 cm rise by 2100 if global greenhouse gas emissions are allowed to continue unabated,” said study co-author Dr John Church of CSIRO Centre for Australian Weather and Climate Research.
“The projections reduce to a rise of between 28 and 61 cm if we follow paths that include very stringent mitigation of global emissions.”
Dr Watson added: “rising sea levels will place increasing stress on the coastal zone – inundation events will become more frequent and adaptation will need to occur. Agencies need to consider the impacts of accelerating sea levels and provide communities with advice and planning directions that are commensurate with the magnitude of the problem.”
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Christopher S. Watson et al. Unabated global mean sea-level rise over the satellite altimeter era. Nature Climate Change, published online May 11, 2015; doi: 10.1038/nclimate2635
