Global warming of 2C would see \u201cextensive, long-term [and] essentially irreversible\u201d losses from the Earth\u2019s ice sheets and glaciers, warns a new report.<\/p>\n\n\n\n
It would also lead to polar oceans that are \u201cice-free\u201d in summer and suffering \u201cessentially permanent corrosive ocean acidification\u201d, the report says.<\/p>\n\n\n\n
The 2023 \u201cstate of the cryosphere<\/a>\u201d report from the International Cryosphere Climate Initiative<\/a> (ICCI) lays out the impacts on Earth\u2019s frozen land and seas from sustained warming at 2C and the \u201ccatastrophic global damage\u201d that would result.<\/p>\n\n\n\n These impacts would include \u201cpotentially rapid, irreversible sea level rise from the Earth\u2019s ice sheets\u201d, the report says, with a \u201ccompelling number of new studies\u201d all pointing to thresholds of sustained ice loss for both Greenland and parts of Antarctica at well-below 2C.<\/p>\n\n\n\n This would commit the world to \u201cbetween 12 and 20 metres\u201d of sea level rise \u201cif 2C becomes the new constant\u201d.<\/p>\n\n\n\n Holding global warming of 2C would also not be enough to \u201cprevent extensive permafrost thaw\u201d, the authors say, bringing additional warming from the resulting CO2 and methane emissions. A 2C world would also see \u201cwidespread negative impacts on key fisheries and species\u201d in polar and near-polar oceans.<\/p>\n\n\n\n First published in 2021<\/a>, the focus of this year\u2019s annual review on how 2C of warming is \u201ctoo high\u201d shows that the aspirational limit of 1.5C in the Paris Agreement<\/a> \u201cis not merely preferable to 2C\u201d, but \u201cthe only option\u201d, the report says.<\/p>\n\n\n\n The ICCI\u2019s Dr James Kirkham<\/a>, chief science advisor at the Ambition on Melting Ice<\/a> high-level group, tells Carbon Brief that the conclusion that 2C is too high for the cryosphere \u201cwon\u2019t come as a surprise at all\u201d to most scientists.<\/p>\n\n\n\n With COP28 in Dubai coming later this month, Kirkham says it is time to make \u201ccrystal clear\u201d that \u201c2C must now be seen as an unacceptable outcome for the world because of the impacts from the cryosphere\u201d.<\/p>\n\n\n\n In this Q&A, Carbon Brief unpacks the report\u2019s findings for the world\u2019s ice sheets, mountain glaciers, permafrost, sea ice and polar oceans.<\/p>\n\n\n\n Past emissions of CO2 and other greenhouse gases (GHGs) have \u201cpushed the planet into a risk zone\u201d, the report warns, with very visible impacts on the cryosphere:<\/p>\n\n\n\n \u201cToday\u2019s 1.2C above pre-industrial already has caused massive drops in Arctic and Antarctic sea ice; loss of glacier ice in all regions across the planet; accelerating loss from both the Greenland and Antarctic ice sheets; extensive permafrost thaw; and rising polar ocean acidification.\u201d<\/p>\n<\/blockquote>\n\n\n\n The implications of these changes stretch beyond the Earth\u2019s poles and mountain regions, the authors note, from accelerating sea level rise<\/a> and disturbed ocean currents<\/a> to declining water resources<\/a> and greater carbon emissions<\/a>.<\/p>\n\n\n\n Nearly all of these changes \u201ccannot be reversed on human timescales\u201d, the authors warn, and they will continue to grow with each additional 10th of a degree of temperature rise. <\/p>\n\n\n\n Kirkham likens the way the cryosphere responds to warming to a \u201cbowling ball once thrown\u201d. He tells Carbon Brief:<\/p>\n\n\n\n \u201cThe changes will continue to roll on long after its initial climatic push because the system has momentum.<\/p>\n<\/blockquote>\n\n\n\n \u201c[This means] that many of the long-term challenges associated with the cryosphere are on the cusp of being locked in by decisions made by policymakers in the next few years, and the awareness in the policy world of this \u2018lock in\u2019 appears lost right now.\u201d<\/p>\n<\/blockquote>\n\n\n\n While the aim of restricting global warming to \u201cwell-below\u201d 2C is set out in the Paris Agreement, the report says the \u201cphysical reality\u201d of the cryosphere\u2019s response to warming means these changes \u201cwould become devastating\u201d well before 2C is reached.<\/p>\n\n\n\n However, warming of 2C is not a \u201cpredetermined outcome\u201d, the authors say, arguing that \u201conly a strong, emergency scale course-correction towards 1.5C\u2026can avert higher temperatures, to slow and eventually halt these cryosphere impacts within adaptable levels\u201d. <\/p>\n\n\n\n A \u201cvery low\u201d future emissions pathway that would keep warming within, or very close to, 1.5C \u2013 the more stringent part of the Paris goal \u2013 remains \u201cphysically, technologically and economically feasible\u201d, the report says. <\/p>\n\n\n\n This is the \u201cSSP1-1.9\u201d pathway from the set of Shared Socioeconomic Pathways<\/a> (SSPs) used in the sixth assessment report<\/a> (AR6) of the Intergovernmental Panel on Climate Change<\/a> (IPCC).<\/p>\n\n\n\n Under this pathway (see table below), fossil fuel emissions decline 40% by 2030 and global warming peaks at 1.6C before declining to around 1.4C by the end of the century. <\/p>\n\n\n\n\n
How can \u2018very low\u2019 emissions slow impacts on the cryosphere?<\/h2>\n\n\n\n
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