Yesterday we took a look at what we have been doing over the past 40 years. Now we take a look at what we will be doing over the rest of the 21st century. It’s a real shocker to look at: All policy scenarios now require an immediate trend breach – this is the biggest challenge mankind has ever faced:
Considering a slightly [but much disputed – as it still excludes biosphere carbon feedbacks!] more optimistic climate sensitivity range in the IPCC AR5 WG1 report of September 2013 (same report, but the part about the physics of climate change) IPCC WG3 in their sub report about climate mitigation now state a somewhat higher confidence that ‘the old 450 Scenario’ (seen here as the light-blue range of 430-480 ppm) offers stabilisation of greenhouse gas concentration at a level that will prevent warming of more than 2 degrees Celsius, on average – as is the official climate target of the international community. Higher GHG concentration, like the dark-blue 480-530 ppm CO2 equivalent scenario offer swiftly decreasing chances warming will be limited to 2 degrees, especially when there’s an early ‘overshoot’ – that is, the longer we postpone action (say another 10 years) – the less likely higher GHG concentration stabilisation scenarios (by 2100) will still be able to be effective (and of course also the smaller the chance this stabilisation will be achieved at all, as the graph clearly shows even pathways towards 720-1000 ppm require immediate stabilisation of global emissions over the current decade.
Conclusion: to get to the relatively safe 430-480 ppm stabilisation scenario we need to bridge an emissions gap with business as usual (the current trend) of well over 600 ppm – as we are now heading towards well over 1000 ppm.
Even the reckless/‘less ambitious’ stabilisation scenarios all require an immediate trend breach – leading to at least a global emissions plateau over the next decade, halting the (currently still accelerating!) annual growth in global emissions.
Big things need to happen globally in the next couple of years – including a global clamp down* on the fossil fuels industry, in all scenarios – as a minimum.
[*) Low-carbon energy sources need to be stepped up drastically in all these scenarios IPCC states – for instance even the scenario leading to 580-720 ppm CO2 equivalents requites a growth of low-carbon energy of 190 percent between 2010 and 2050 – and that is the scenario that leads to several degrees of warming, and likely activation of positive climate feedbacks, so far from the official 2 degrees target. The 430-480 Scenario needs the low-carbon energy share to more than quadruple globally, in the 40 years between 2010 and 2050.]
We are really talking about the biggest challenge mankind has ever faced.
© Rolf Schuttenhelm | www.bitsofscience.org