25.1. Introduction and Major Conclusions from Previous Assessments

Australasia is defined here as lands, territories, offshore waters, and oceanic islands of the exclusive economic zones of Australia and New Zealand. Both countries are relatively wealthy, with export-led economies. Both have Westminster-style political systems and have a relatively recent history of non-indigenous settlement (Australia in the late 18th, New Zealand in the early 19th century). Both retain significant indigenous populations.

Principal findings from the IPCC Fourth Assessment Report (AR4) for the region were (Hennessy et al., 2007):

1. • Consistent with global trends, Australia and New Zealand had experienced warming of 0.4°C to 0.7°C since 1950 with changed rainfall patterns and sea level rise of about 70 mm across the region; there had also been a greater frequency and intensity of droughts and heat waves, reduced seasonal snow cover, and glacial retreat.

2. • Impacts from recent climate changes were evident in increasing stresses on water supply and agriculture, and changed natural ecosystems; some adaptation had occurred in these sectors but vulnerability to extreme events such as fire, tropical cyclones, droughts, hail, and floods remained high.

3. • The climate of the 21st century would be warmer (virtually certain), with changes in extreme events including more intense and frequent heat waves, fire, floods, storm surges, and droughts but less frequent frost and snow (high confidence), reduced soil moisture in large parts of the Australian mainland and eastern New Zealand but more rain in western New Zealand (medium confidence).

4. • Significant advances had occurred in understanding future impacts on water, ecosystems, indigenous people and health, together with an increased focus on adaptation; potential impacts would be substantial without further adaptation, particularly for water security, coastal development, biodiversity, and major infrastructure, but impacts on agriculture and forestry would be variable across the region, including potential benefits in some areas.

5. • Vulnerability would increase mainly due to an increase in extreme events; human systems were considered to have a higher adaptive capacity than natural systems.

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