Global warming in the context of 2000 years of Australian alpine temperature and snow cover

Abstract

Annual resolution reconstructions of alpine temperatures are rare, particularly for the Southern Hemisphere, while no snow cover reconstructions exist. These records are essential to place in context the impact of anthropogenic global warming against historical major natural climate events such as the Roman Warm Period (RWP), Medieval Climate Anomaly (MCA) and Little Ice Age (LIA). Here we show for a marginal alpine region of Australia using a carbon isotope speleothem reconstruction, warming over the past five decades has experienced equivalent magnitude of temperature change and snow cover decline to the RWP and MCA. The current rate of warming is unmatched for the past 2000 years and seasonal snow cover is at a minimum. On scales of several decades, mean maximum temperatures have undergone considerable change ≈ ± 0.8 °C highlighting local scale susceptibility to rapid temperature change, evidence of which is often masked in regional to hemisphere scale temperature reconstructions.

Snow Cover Change as a Climate Indicator in Brunswick Peninsula, Patagonia

“…A recent study of snow cover variability in Aysén basin, northern Patagonia, using MODIS data for period 2000-2016 period (Pérez et al, 2018), shows a decreasing but non-significant trend of 20 km 2 year −1 in snow covered area. Similar trends have been detected in the Australian Alps where the maximum snow depth has declined by up to 15% since the 1960s, particularly in spring (McGowan et al, 2018). Model predictions suggest this trend will continue along with a reduction in length of the snow season in response to global warming (Hennessy et al, 2008;McGowan et al, 2018).…”

“…Similar trends have been detected in the Australian Alps where the maximum snow depth has declined by up to 15% since the 1960s, particularly in spring (McGowan et al, 2018). Model predictions suggest this trend will continue along with a reduction in length of the snow season in response to global warming (Hennessy et al, 2008;McGowan et al, 2018). In the European Alps, longterm observations show negative trends in snow depth and snow duration over the past decades (Beniston et al, 2018).…”

“…Climate change particularly affects snow-covered areas (Hughes, 2003;IPCC, 2013), since even small changes in the surface-atmospheric energy balance may cause significant decreases in snow cover, affecting the local hydrology, associated ecosystems, hydroelectric power generation, and tourism activities (Gobiet et al, 2014;McGowan et al, 2018). Therefore, if climate trends can be detected, valuable information can be provided to decision makers and stakeholeders.…”

Evidence of wet-dry cycles and mega-droughts in the Eemian climate of southeast Australia

“…1) under New South Wales Parks and Wildlife Scientific licence SL100538. The caves are located at the northern end of the Snowy Mountains, at an elevation where the water balance changes from an energy (demand) to supply (precipitation) limited system 23,24 . The caves were formed through karstification of the Yarrangobilly Limestone, a massive Silurian limestone formation with an extent of ~ 1.4 km by 14 km and a maximum depth of ~ 450 m 25 .…”

Predicting species and community responses to global change in Australian mountain ecosystems using structured expert judgement

“…Since 1979, mean spring temperatures in the Australian Alps have risen by approximately 0.4 ºC and annual precipitation has fallen by 6% (Wahren et al 2013), with a consequent decline in snow pack depth (Sanchez-Bayo & Green 2013). Snow cover in Australia is now at its lowest in the past 2000 years (McGowan et al 2018). These climatic changes correlate with changes in floristic structure, abundance and diversity (Wahren et al 2013;Camac et al 2015) and increases in fire frequency and severity (Camac et al 2017;Zylstra 2018).…”