[{"data":1,"prerenderedAt":237},["ShallowReactive",2],{"\u002Farticles\u002Fsea-level":3},{"id":4,"title":5,"body":6,"description":229,"extension":230,"image":28,"meta":231,"navigation":232,"path":233,"seo":234,"stem":235,"__hash__":236},"content\u002Farticles\u002Fsea-level.md","Are the seas rising faster because of us?",{"type":7,"value":8,"toc":220},"minimark",[9,13,18,21,29,32,35,38,42,45,48,51,55,58,61,64,68,71,74,77,81],[10,11,12],"p",{},"Nobody disputes that sea level is rising. The real questions are how fast, whether it is speeding up, how much is our doing, and what it means for a given stretch of Canadian coast.",[14,15,17],"h2",{"id":16},"a-rise-that-began-before-industry","A rise that began before industry",[10,19,20],{},"The longest global record comes from tide gauges. In 2014, Svetlana Jevrejeva and her colleagues combined 1,277 tide-gauge records going back to 1807 to reconstruct global sea level up to 2009.",[10,22,23],{},[24,25],"img",{"alt":26,"loading":27,"src":28},"Global sea level reconstruction from 1807 to 2009, Jevrejeva et al. 2014, as plotted by the CO2 Coalition","lazy","\u002Fimages\u002Fcharts\u002Fextracted\u002F102-Sea-level-Jevrejeva-2014.webp",[10,30,31],{},"The curve wanders, and even dips, through the early 1800s, then climbs fairly steadily from around the 1860s. That timing matches the end of the Little Ice Age, a cool period lasting from the early 1300s to the mid-1800s. An earlier study by the same group found that the acceleration began at the end of the 18th century, with roughly 6 centimetres of rise in the 1800s and 19 centimetres in the 1900s.",[10,33,34],{},"Industrial emissions came much later. By 1900, the world had released less than 3 per cent of all the carbon dioxide from fossil fuels and industry emitted to date, and by 1950 only about 12 per cent. Whatever started the rise, it was not our emissions.",[10,36,37],{},"Jevrejeva’s reconstruction gives a 20th-century average of about 1.9 millimetres a year. The IPCC puts total global rise between 1901 and 2018 at about 20 centimetres.",[14,39,41],{"id":40},"is-it-speeding-up","Is it speeding up?",[10,43,44],{},"The honest answer is yes, though how much has long been debated. Jevrejeva’s team measured an acceleration of only 0.02 millimetres per year, per year, across 1807 to 2009. They also found a natural cycle of about 60 years riding on top of the long-term trend. In 2011, James Houston and Robert Dean analysed 57 American tide gauges and found small average decelerations from 1930 to 2010.",[10,46,47],{},"Satellites, which have measured almost the entire ocean surface since 1993, tell a different story. A 2024 NASA-led study found that global sea level rose 111 millimetres from 1993 to 2023, and that the yearly rate grew from about 2.1 millimetres in 1993 to about 4.5 millimetres in 2023. The IPCC reports average rates of 1.3 millimetres a year for 1901–1971, 1.9 for 1971–2006 and 3.7 for 2006–2018. It judges that human influence was very likely the main driver of these increases since at least 1971.",[10,49,50],{},"The fair summary: the rise began naturally, it has been faster in recent decades, and the IPCC attributes most of the rise since 1971 to us. But the satellite record is only about 30 years long, half of one of those 60-year cycles. Its researchers do try to account for natural swings; a longer record will settle the question.",[14,52,54],{"id":53},"in-canada-the-land-moves-too","In Canada, the land moves too",[10,56,57],{},"What matters on a given beach is relative sea level: the sea compared with the land. Much of Canada is still adjusting to the removal of the ice sheets that covered it in the last ice age.",[10,59,60],{},"Around Hudson Bay, close to the centre of the old ice sheet, the coast is rising 10 millimetres a year or more. At Churchill, Manitoba, sea level has been falling at 9.3 millimetres a year. On the old edges of the ice sheet the land is sinking instead, by up to about 2 millimetres a year in parts of Nova Scotia and along the Beaufort Sea coast. At Halifax, sea level rose about 3.3 millimetres a year during the 20th century, well above the global average.",[10,62,63],{},"On the Fraser River delta, soft sediments compacting under their own weight cause the lowlands to sink 1 to 2 millimetres a year. Where new fill or buildings have loaded the ground, the rate reaches 3 to 8 millimetres a year. By contrast, GPS stations near Vancouver show negligible vertical motion.",[14,65,67],{"id":66},"projections-tide-gauges-and-dikes","Projections, tide gauges and dikes",[10,69,70],{},"The IPCC’s very-high-emissions scenario, SSP5-8.5, gives a likely global rise of 63 to 101 centimetres by 2100, measured from a 1995–2014 baseline. A rise approaching 2 metres “cannot be ruled out,” though the IPCC has low confidence in it. To reach even the low end, the seas would need to average about 6.6 millimetres a year over those 95 years, and more than 10 millimetres a year for the high end. That is several times the 20th-century tide-gauge rate and above even today’s satellite rate. The scenario itself is contested: researchers Zeke Hausfather and Glen Peters have urged colleagues to stop treating it as the most likely outcome.",[10,72,73],{},"Canada’s Changing Climate Report projects more than 75 centimetres of rise by 2100 at sinking Atlantic sites under its high-emissions scenario, and more than 150 centimetres at Halifax under an enhanced version of it. Halifax’s 20th-century rate, carried forward, would give roughly 25 centimetres by 2100. Meanwhile, the same report expects sea level around Hudson Bay to keep falling.",[10,75,76],{},"None of this means doing nothing. It means building for what is actually happening, place by place. British Columbia’s 2011 guidance asks planners to allow for 0.5 metres of rise by 2050 and 1 metre by 2100. On the Chignecto Isthmus, where dikes first built in the late 1600s protect the only land link between Nova Scotia and the rest of Canada, a $650 million federal-provincial project will raise them. A rise measured in millimetres a year gives time to raise dikes in stages, update flood maps and keep checking the tide gauges.",[14,78,80],{"id":79},"references","References",[82,83,84,101,114,123,132,140,152,164,177,189,201,212],"ol",{},[85,86,87,88,95,96,100],"li",{},"Jevrejeva, S., Moore, J.C., Grinsted, A., Matthews, A.P. and Spada, G. (2014). ",[89,90,94],"a",{"href":91,"rel":92},"https:\u002F\u002Fnora.nerc.ac.uk\u002Fid\u002Feprint\u002F504181",[93],"nofollow","Trends and acceleration in global and regional sea levels since 1807",". ",[97,98,99],"em",{},"Global and Planetary Change",", 113, 11–22.",[85,102,103,104,109,110,113],{},"Jevrejeva, S., Moore, J.C., Grinsted, A. and Woodworth, P.L. (2008). ",[89,105,108],{"href":106,"rel":107},"https:\u002F\u002Fnora.nerc.ac.uk\u002Fid\u002Feprint\u002F5399\u002F",[93],"Recent global sea level acceleration started over 200 years ago?"," ",[97,111,112],{},"Geophysical Research Letters",", 35, L08715.",[85,115,116,117,122],{},"IPCC (2021). ",[89,118,121],{"href":119,"rel":120},"https:\u002F\u002Fwww.ipcc.ch\u002Freport\u002Far6\u002Fwg1\u002Fdownloads\u002Freport\u002FIPCC_AR6_WGI_SPM.pdf",[93],"Climate Change 2021: The Physical Science Basis, Summary for Policymakers",", paragraphs A.1.7 and B.5.3.",[85,124,125,126,131],{},"Encyclopaedia Britannica. ",[89,127,130],{"href":128,"rel":129},"https:\u002F\u002Fwww.britannica.com\u002Fscience\u002FLittle-Ice-Age",[93],"Little Ice Age",".",[85,133,134,135,131],{},"Our World in Data, based on the Global Carbon Project. ",[89,136,139],{"href":137,"rel":138},"https:\u002F\u002Fgithub.com\u002Fowid\u002Fco2-data",[93],"CO₂ emissions dataset",[85,141,142,143,95,148,151],{},"Houston, J.R. and Dean, R.G. (2011). ",[89,144,147],{"href":145,"rel":146},"https:\u002F\u002Fdoi.org\u002F10.2112\u002FJCOASTRES-D-10-00157.1",[93],"Sea-level acceleration based on U.S. tide gauges and extensions of previous global-gauge analyses",[97,149,150],{},"Journal of Coastal Research",", 27(3), 409.",[85,153,154,155,95,160,163],{},"Hamlington, B.D. et al. (2024). ",[89,156,159],{"href":157,"rel":158},"https:\u002F\u002Fdoi.org\u002F10.1038\u002Fs43247-024-01761-5",[93],"The rate of global sea level rise doubled during the past three decades",[97,161,162],{},"Communications Earth & Environment",", 5.",[85,165,166,167,172,173,176],{},"Greenan, B.J.W., James, T.S., Loder, J.W. et al. (2019). ",[89,168,171],{"href":169,"rel":170},"https:\u002F\u002Fchangingclimate.ca\u002FCCCR2019\u002Fchapter\u002F7-0\u002F",[93],"Changes in oceans surrounding Canada",", Chapter 7 in ",[97,174,175],{},"Canada’s Changing Climate Report",". Government of Canada.",[85,178,179,180,95,185,188],{},"Mazzotti, S., Lambert, A., Van der Kooij, M. and Mainville, A. (2009). ",[89,181,184],{"href":182,"rel":183},"https:\u002F\u002Fdoi.org\u002F10.1130\u002FG25640A.1",[93],"Impact of anthropogenic subsidence on relative sea-level rise in the Fraser River delta",[97,186,187],{},"Geology",", 37(9), 771–774.",[85,190,191,192,95,197,200],{},"Hausfather, Z. and Peters, G.P. (2020). ",[89,193,196],{"href":194,"rel":195},"https:\u002F\u002Fdoi.org\u002F10.1038\u002Fd41586-020-00177-3",[93],"Emissions – the ‘business as usual’ story is misleading",[97,198,199],{},"Nature",", 577, 618–620.",[85,202,203,204,131],{},"Government of British Columbia (2011). ",[89,205,208,209],{"href":206,"rel":207},"https:\u002F\u002Fnews.gov.bc.ca\u002Freleases\u002F2011FOR0050-000507",[93],"News release on ",[97,210,211],{},"Climate Change Adaptation Guidelines for Sea Dikes and Coastal Flood Hazard Land Use",[85,213,214,215,131],{},"Housing, Infrastructure and Communities Canada (2025). ",[89,216,219],{"href":217,"rel":218},"https:\u002F\u002Fwww.canada.ca\u002Fen\u002Fhousing-infrastructure-communities\u002Fnews\u002F2025\u002F03\u002Fprotecting-the-chignecto-isthmus-against-climate-change.html",[93],"Protecting the Chignecto Isthmus against climate change",{"title":221,"searchDepth":222,"depth":222,"links":223},"",2,[224,225,226,227,228],{"id":16,"depth":222,"text":17},{"id":40,"depth":222,"text":41},{"id":53,"depth":222,"text":54},{"id":66,"depth":222,"text":67},{"id":79,"depth":222,"text":80},"Seas have been rising since the Little Ice Age ended in the mid-1800s, long before most emissions. Satellites show a faster rate since 1993, but for Canadians the local picture matters more, because some of our coasts are sinking while others are rising out of the sea.","md",{},true,"\u002Farticles\u002Fsea-level",{"title":5,"description":229},"articles\u002Fsea-level","lBZ9CaFYg83KeNKNGhbogWgVVnxv6fm0r-XXRXVCnb4",1793389400892]