Abstract
Outputs from new state-of-the-art climate models under the Coupled Model
Inter-comparison Project phase 6 (CMIP6) promise improvement and
enhancement of climate change projections information for Australia.
Here we focus on three key aspects of CMIP6: what is new in these
models, how the available CMIP6 models evaluate compared to CMIP5, and
their projections of the future Australian climate compared to CMIP5
focussing on the highest emissions scenario. The CMIP6 ensemble has
several new features of relevance to policy-makers and others, for
example the integrated matrix of socio-economic and concentration
pathways. The CMIP6 models show incremental improvements in the
simulation of the climate in the Australian region, including a reduced
equatorial Pacific cold-tongue bias, slightly improved rainfall
teleconnections with regional climate drivers, improved representation
of atmosphere and ocean extreme heat events, as well as dynamic sea
level. However, important regional biases remain, evident in the
excessive precipitation over the Maritime Continent and precipitation
pattern biases in the nearby tropical convergence zones. Projections of
temperature and rainfall from the available CMIP6 ensemble broadly agree
with those from CMIP5, except for a group of CMIP6 models with higher
climate sensitivity and greater warming and increase in some extremes
after 2050. CMIP6 rainfall projections are similar to CMIP5, but the
ensemble examined has a narrower range of rainfall change in summer in
the north and winter in the south. Overall, future national projections
are likely to be similar to previous versions but perhaps with some
areas of improved confidence and clarity.