Editing IPCC:AR6/WGII/Chapter-2 (section)

==== 2.5.2.9 Risks to Polar Tundra Ecosystems ====

<div id="h3-41-siblings" class="h3-siblings"></div>

For boreal–tundra systems, AR5 projected the transformation of species composition, land cover and permafrost extent, decreasing albedo and increasing GHG emissions ( ''medium confidence'' ). SR1.5 classified tundra and boreal forests as particularly vulnerable to degradation and encroachment by woody shrubs ( ''high confidence'' ). The SROCC projected climate-related changes to arctic hydrology, wildfires and abrupt thaw ( ''high confidence'' ) and the broad disappearance of arctic near-surface permafrost this century, with important consequences for global climate ( ''very high confidence'' ) ''.'' [https://www.ipcc.ch/report/ar6/wg2/chapter/chapter-2 Chapter 2] of AR6 has focused on new key findings about observed and projected changes in tundra vegetation and related hydrology, with implications for feedbacks to the climate system.

Due to the rapid warming at high northern latitudes, the Arctic tundra is one of the terrestrial biomes where climate change impacts are already clearly visible ( [[#Settele--2014|Settele et al., 2014]] ; [[#Uboni--2016|Uboni et al., 2016]] ). Climate models project that warming of the Arctic is likely to continue at more than double the global rate. Compared to the period 1995–2014, mean annual surface air temperatures in the Arctic tundra are projected to increase by 7.9°C–10°C by the end of the century in scenarios of high GHG emissions (RCP7.0 and RCP8.5). In scenarios of low GHG emissions (RCP1.9 and RCP2.6), the projected increase is 2.6°C–3.2°C ( [[#Lee--2021|Lee et al., 2021]] ). The Arctic is also projected to have amongst the largest increases in precipitation globally, but with ''high'' uncertainty. In contrast to climate change, LUC is projected to be very low in Arctic tundra systems ( [[#van%20Asselen--2013|van Asselen and Verburg, 2013]] ).

Models of vegetation response to climate project acceleration in the coming decades of observed increases in shrub dominance and boreal forest encroachment that have been driven by recent warming ( [[#Settele--2014|Settele et al., 2014]] ), leading to a shrinking of the area of tundra globally ( ''medium confidence'' ) ( [[#Mod--2016|Mod and Luoto, 2016]] ; [[#Gang--2017|Gang et al., 2017]] ). Simulating changes in tundra vegetation is complicated by permafrost dynamics (e.g., the formation of thaw ponds and draining of existing ponds), changes in precipitation and low nutrient availability (which may promote the abundance of graminoids) ( [[#van%20der%20Kolk--2016|van der Kolk et al., 2016]] ). Changes in vegetation, when combined with warming and increased precipitation effects on soil thawing and carbon cycling, are projected to modify GHG emissions and have biophysical feedbacks to regional and global climate. High uncertainty in modelled carbon cycle changes arises from differences between the vegetation models ( [[#Nishina--2015|Nishina et al., 2015]] ; [[#Ito--2016|Ito et al., 2016]] ). In addition, climate change is expected to strongly interact with other factors, such as fire, to further increase uncertainty in projections of tundra ecosystem function ( [[#Jiang--2017|Jiang et al., 2017]] ).

<div id="2.5.2.10" class="h3-container"></div>

<span id="committed-impacts-of-climate-change-on-terrestrial-ecosystems-and-implications-of-overshoot"></span>