Man-driven sea-level rise since 1970

Together with colleagues from CSIRO (John Church) and the universities of Bremen (Ben Marzeion), Innsbruck (Kristin Richter) and Liege (Xavier Fettweis and Cecile Agosta), I have published an article in Nature Climate Change on the human impact on sea-level rise.

The paper shows that the majority of the observed sea-level rise since the 1970's is caused by the human influence on the climate.

We found this by comparing the observed global mean sea-level change to sea level estimates from models. 

Our main findings 

The combined influence of human forcing (greenhouse gases and aerosols) is small in the beginning of the century (only 15%), but after 1970 the majority of the observed sea-level rise is a direct response to human influence (nearly 70%), with an increasing percentage up to the present day.

Internal variability and natural forcings (mostly volcanic eruptions) impact sea level on yearly to decadal time scales. Over the 20th century as a whole, their impact is small and explains little of the observed sea-level trend.

The delayed response of the glaciers and ice sheets to the warmer temperatures after the Little Ice Age (1300-~1870 AD) explains a lot of the observed sea-level change before 1950 (nearly 70%), but very little after 1970 (less than 10%).

Overall, the models explain about three quarters of the observed rise since 1900 and almost all of the rise over recent decades (almost 90% since 1970). The causes for these differences could be both in the model estimates (for instance an underestimated ice sheet contribution) and in the lower quality sea level observations prior to the satellite record. 

Tipping the scales 

In conclusion, our paper shows that the driving factors of sea-level change have shifted over the course of the 20th century. Human influence has now become the dominant driving force for sea-level rise and this will continue until greenhouse gas emissions are reduced. 

A. B. A. Slangen, J. A. Church, C. Agosta, X. Fettweis, B. Marzeion and K. Richter (2016) Anthropogenic forcing dominates global mean sea-level rise since 1970, Nature Climate Change, 6, 701-705, DOI: 10.1038/nclimate2991

A read-only version of the paper for those without access to Nature Climate Change is available here.


The paper is also mentioned in the editorial of this issue of Nature Climate Change.  

Questions? 

Tweet me (@AimeeSlangen) or email aimee.slangen [at] gmail.com 

Media Coverage

* News & Views in Nature Climate Change
* The Conversation 
* Climate Central
* COSMOS magazine 
* CSIRO news blog
* NWO press release (in Dutch)
* Utrecht University (in Dutch)
* Austrian press release (in German) 
* Der Standard (in German)
* BBC News 
* DeSmogBlog (reprint from the Conversation) 


[Infographic by A. Slangen and CSIRO]