Public understanding of climate change-related sea-level rise

and ice sheets and ice caps on planet Earth melted’, and what was the fastest time period over which this could occur. The largest group (38.8%) of respondents underestimated the maxi- mum amount of sea-level rise possible, selecting ‘about 30 m’. The next largest group (22.3%) chose a figure broadly in line with current estimates of 66.07 m [29], selecting ‘about 60 m’. The remaining 38.9% of respondents overestimated total maximum sea-level rise, selecting ‘about 120 m’ (17%), ‘about 240 m’ (10.9%) and ‘more than 500 m’ (11%). In selecting the ‘fastest period of time’ over which their perceived maximum amount of sea- level rise could occur, respondents overestimated the speed at which all the planet’s ice could melt. While scientists suggest that such melting could take place under a sustained warming climate over a period of thousands of years [30, 31], the majority of respondents overestimated how fast the planet’s ice could melt, selecting ‘decades’ (33.1%) or ‘centuries’ (39%). A smaller group (11.6%) of respondents answered in line with the science by selecting ‘thousands of years’. The remaining respondents selected ‘tens of thousands’ (3.2%) or ‘hundreds of thou- sands’ (2.7%) of years, or acknowledged that ‘I really don’t know’ (10.4%). Public identified melting sea ice as causing sea-level rise Respondents were also asked to identify and rank the major causes of sea-level rise from a ten- item list that included melting ice sheets, melting land-based glaciers, melting sea ice, thermal

expansion, and land subsidence. No definitions of these phrases were provided as our inten- tion was to gauge people’s understanding of sea-level rise from existing sources of information, such as the media. While climate scientists and the media make efforts when communicating with publics to not identify melting of Arctic and Antarctic sea ice (which is widely covered in the media) as causing sea-level rise, 28.7% of respondents identified this as their top ranked cause of sea-level rise (see Fig 2A). Encouragingly, other respondents’ top ranked causal Fig 2. Major contributors to sea-level rise. Respondents were asked to identify and rank the major contributors to sea-level rise. In (a) we show respondents’ top ranked cause of sea-level rise (causes selected by fewer than 2% of respondents are not shown). In (b) we show the sum of the top three causes identified by respondents (causes ranked by fewer than 10% of respondents are not shown). https://doi.org/10.1371/journal.pone.0254348.g002 PLOS ONE Public understanding of climate change-related sea-level rise PLOS ONE | https://doi.org/10.1371/journal.pone.0254348 July 9, 2021 5 / 12