Editing IPCC:AR6/WGI/TS (section)

===== TS.4.3.2.3 Australasia =====

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'''Additional regional changes in Australasia, besides those features described in Section TS.4.3.1, include a significant decrease in April to October rainfall in the south-west of the state of Western Australia, observed from 1910 to 2019 and attributable to human influence ( ''high confidence'' ), which is ''very likely'' to continue in future. Agricultural and ecological droughts and hydrological droughts have increased over Southern Australia ( ''medium confidence'' ), and meteorological droughts have decreased over Northern and Central Australia ( ''medium confidence'' ). Relative sea level has increased over the period 1993–2018 at a rate higher than GMSL around Australasia ( ''high confidence'' ). Sandy shorelines have retreated around the region, except in Southern Australia, where a shoreline progradation rate of 0.1 m yr <sup>–1</sup> has been observed.''' '''In the future, heavy precipitation and pluvial flooding are ''very likely'' to increase over Northern Australia and Central Australia, and they are ''likely'' to increase elsewhere in Australasia for global warming levels (GWLs) exceeding 2°C and with ''medium confidence'' for a 2°C GWL. Agricultural and ecological droughts are projected to increase in Southern and Eastern Australia ( ''medium confidence'' ) for a 2°C GWL. Fire weather is projected to increase throughout Australia ( ''high confidence'' ) and New Zealand ( ''medium confidence'' ). Snowfall is expected to decrease throughout the region at high altitudes in both Australia ( ''high confidence'' ) and New Zealand ( ''medium confidence'' ), with glaciers receding in New Zealand ( ''high confidence'' ). Links to chapters 11.4, Table 11.6, 12.3, 12.4.3, Atlas.6.4, Atlas.6.5'''
In addition to the main changes summarized above and in Section TS.4.3.1, further details are given below.

'''Heat and cold:''' Observed and projected increases in mean temperature and a shift toward heat extreme characteristics are broadly similar to the generic pattern described in Section TS.4.3.1. Links to chapters 11.9, 12.4.3.1, Atlas.6

'''Wet and dry:''' There is ''medium confidence'' that heavy precipitation has increased in Northern Australia since 1950. Annual mean precipitation is projected to increase in the south and west of New Zealand ( ''medium confidence'' ) and is projected to decrease in south-west Southern Australia ( ''high confidence'' ), Eastern Australia ( ''medium confidence'' ), and in the north and east of New Zealand ( ''medium confidence'' ) for a GWL of 2°C. There is ''medium confidence'' that river flooding will increase in New Zealand and Australia, with higher increases in Northern Australia. Aridity is projected to increase with ''medium confidence'' in Southern Australia ( ''high confidence'' in south-west Southern Australia), Eastern Australia ( ''medium confidence'' ) and in the north and east of New Zealand ( ''medium confidence'' ) for GWLs around 2°C. Links to chapters 11.4, 11.9, Table 11.6, 12.4.3.2, Atlas.6.2

'''Wind:''' Mean wind speeds are projected to increase in parts of north-eastern Australia ( ''medium confidence'' ) by the end of the 21st century under high CO <sub>2</sub> emissions scenarios. TCs in north-eastern and north Australia are projected to decrease in number ( ''high confidence'' ) but increase in intensity except for ‘east coast lows’ ( ''low confidence'' ). Links to chapters 12.4.3.3

'''Snow and ice:''' Observations in Australia show that the snow season length has decreased by 5% in the last five decades. Furthermore, the date of peak snowfall in Australia has advanced by 11 days over the last 5 decades. Glacier ice volume in New Zealand has decreased by 33% from 1977 to 2018. Links to chapters 12.4.3.4, Atlas.6.2

'''Coastal and oceanic:''' Observed changes in marine heatwaves (MHWs) over the 20th century in the region show an increase in their occurrence frequency, except along the south-east coast of New Zealand, an increase in duration per event, and the total number of MHW days per decade, with the change being stronger in the Tasman Sea than elsewhere. The present day 1-in-100-year ETWL is between 0.5–2.5 m around most of Australia, except the north-western coast where 1-in-100-year ETWL can be as high as 6–7 m. Links to chapters Box 9.1, 12.3.1.5, 12.4.3.5

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