Editing IPCC:AR6/WGII/Chapter-11 (section)

=== 11.2.1 Observed Climate Change ===

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Regional climate change has continued since AR5 was released in 2014, with trends exacerbating many extreme events ( ''very high confidence'' ). The following changes are quantified with references in Tables 11.2a and 11.2b. The region has continued to warm (Figure 11.1), with more extremely high temperatures and fewer extremely low temperatures. Snow depths and glacier volumes have declined. Sea level rise and ocean acidification have continued. Northern Australia has become wetter, while April–October rainfall has decreased in south-western and south-eastern Australia. In New Zealand, most of the south has become wetter, while most of the north has become drier (Figure 11.2). The frequency, severity and duration of extreme fire weather conditions have increased in southern and eastern Australia and eastern New Zealand. Changes in extreme rainfall are mixed. There has been a decline in tropical cyclone frequency near Australia.

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'''Figure 11.1 |''' '''Observed temperature changes in Australia and New Zealand.''' Annual temperature change time series are shown for 1910–2019. Mean annual temperature trend maps are shown for 1960–2019 using contours for Australia and individual sites for New Zealand. Data courtesy of BOM and NIWA.

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'''Figure 11.2 |''' '''Observed rainfall changes in Australia and New Zealand.''' Rainfall change time series for 1900–2019 are shown for Northern Australia (December–February: DJF), southwest Australia (June–August: JJA) and southeast Australia (JJA). Dashed lines on the maps for Australia show regions used for the time series. Rainfall trend maps are shown for 1960–2019 (DJF and JJA) using contours for Australia and individual sites for New Zealand. Areas of low Australian rainfall (less than 0.25 mm/day) are shaded white in JJA. Data courtesy of BOM and NIWA.

Reliable measurements are limited for some types of storms, particularly thunderstorms, lightning, tornadoes and hail ( [[#Walsh--2016|Walsh et al., 2016]] ). Many high-impact events are a combination of interacting physical processes across multiple spatial and temporal scales (e.g., fires, heatwaves and droughts), and better understanding of these extreme and compound events is needed ( [[#Zscheischler--2018|Zscheischler et al., 2018]] ).

Some of the observed trends and events can be partly attributed to anthropogenic climate change, as documented in Chapter 16. Examples include regional warming trends and sea level rise (SLR), terrestrial and marine heatwaves, declining rainfall and increasing fire weather in southern Australia and extreme rainfall and severe droughts in New Zealand.

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