Amongst the G20 countries, Australia’s emission reduction target – a reduction of 26-28% on a 2005 baseline – is unusually weak, nowhere near what is required for us to play our fair share in meeting a 2°C Paris target.
The impacts that we are experiencing now at a ~1°C rise in average temperature are the forerunners of rapidly escalating risks as the temperature rises towards 2°C and beyond. An overview of these risks – worsening extreme weather, damage to natural ecosystems, disproportionate impacts on the poor and vulnerable – is given by the ‘burning embers diagram’ of the Intergovernmental Panel on Climate Change (IPCC). The series reveals a striking trend – as the science of climate impacts advances, severe impacts are now expected at more modest increases in temperature
Importantly, the graph from IPCC above shows the burning embers approach dispels the myth that a 2°C rise in global average temperature is a ‘safe’ level of climate change.
Another common problem is the failure to understand that climate impacts increase much faster than temperature increases. The impacts of climate change don’t just increase in proportion to the rise in global average temperature. New studies warn that a warming of 2°C in Australia could lead to extreme temperatures of 3.2°C above those experienced now at ~1°C above pre-industrial levels. In reality, we are likely to experience a nearly three-fold acceleration of extremes compared to changes in average temperatures.
This could lead, for example, to record high temperatures of 50°C in Sydney or Melbourne by 2040-2050 under just a 2°C rise in average temperature (Lewis et al. 2017).
Modest rises in global average temperature could also lead to the crossing of ‘tipping points’ in ecosystems or parts of the physical climate system, where surprisingly rapid and often irreversible changes can occur with a small increase in temperature (Lenton et al. 2008; Figure 18). Examples include coral reefs, the Greenland ice sheet, Siberian permafrost and North Atlantic Ocean circulation. We are already witnessing the crossing of a tipping point here in Australia – extended periods of increases of 1 or 2°C in water temperature over the Great Barrier Reef have changed bleaching from sporadic and isolated to massive, widespread and with high rates of mortality (Hughes et al. 2017).
Several other tipping points, in addition to coral reefs, are vulnerable to tipping within the Paris range of temperature rise (Schellnhuber et al. 2016).
The IPCC uses a synthesis of thousands of peer-reviewed scientific papers to assess the degree of risk at increasing levels of global average temperature.
› There is a significant difference in the degree of risk between the 1.5°C and 2.0°C Paris targets, with higher risks of damage to natural ecosystems and more intense and/or frequent extreme weather events for the 2.0°C target.
At a 2.0°C temperature rise, there is a high level of risk for 3 of the 5 categories – impacts on natural ecosystems, extreme weather events, and impacts on the most vulnerable. That is, a 2.0°C temperature rise is not a “safe” level of climate change.
4.0°C temperature rise (business-as-usual) would lead to a vastly different world, with very high risks to many natural ecosystems and highly damaging impacts on the most vulnerable.
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Information taken from the Climate Council’s
Critical Decade 2017: Accelerating Climate Action report