The IPCC’s recently-released report, Climate Change 2021: the Physical Science Basis has issued the strongest call yet for urgent and deep cuts to be made to global greenhouse gas emissions.
The Working Group I Report says the window in which to deliver the “deep emissions cuts” needed to prevent the worst impacts of climate change is closing rapidly.
A key message from the report is that rapid reductions in emissions are required this decade to prevent long-term ecological and climate breakdown, with every fraction of a degree making a huge difference in avoiding a climate disaster.
The IPCC’s report five emission scenarios
The report examines five illustrative scenarios, which are:
- Doubling of carbon emissions by 2050
- Doubling of carbon emissions by 2100
- Carbon emissions stay at current levels to mid-century
- Net-zero after 2050, and net negative emissions later in the century
- Net-zero around 2050, and net negative emissions later in the century
The bad news is that in all five scenarios, the best estimate is that we will pass 1.5C in the 2030s, even under the rapid mitigation scenarios.
The lowest scenario for carbon emissions was designed to create a pathway to limit warming to 1.5C. So, if your organisation is committed to reach net-zero by around mid-century, then this scenario is the only one realistically available, provided you act now to reduce your emissions significantly this decade.
So how much carbon can we still emit under a 1.5C scenario? This is what the next section on the remaining carbon budget will answer.
Carbon budget – how much carbon can we still emit?
The main driver of long-term warming is the total cumulative emissions of greenhouse gases over time. Carbon budgets are based on the fact that the amount of global warming can be approximated to cumulative carbon emissions.
We have a 50/50 chance to limit warming to 1.5C if we stay within a global carbon budget of 500 billion tonnes. At pre-pandemic global emission rates, this gives us under 11 years before we exceed 1.5C.
If we want a better chance – two in three – of achieving around 1.5C of warming by mid-century, then we can emit just 400 billion tonnes globally, and we have even less time to act.
Scenarios versus risk management
The problem with using these scenarios is that organisations tend to overlook the uncertainty that is involved with these scenarios. To say that we can emit 500 billion tonnes of carbon and still stay at around 1.5C of warming is incorrect – it simply gives a 50/50 chance that this will be the outcome. And at 400 billion tonnes, we have a two thirds chance of getting to around 1.5C.
Those odds are OK but not great. If a new product or service had a one-in-two or a one-in-three chance of being unsuccessful, you might want to invest further resources in a solution to ensure a higher chance of success. It should be the same for your business’ climate response.
Where to from here?
If we make deep cuts to emissions now, and keep going to rapidly decarbonise by 2040 or earlier then we may have a chance of keeping temperature increase to a safe level. We only have a small carbon budget remaining to limit warming to 1.5C. Meeting this goal is still achievable if we act quickly and decisively.
Starting today, making deep emissions cuts, and persisting on this path for years is the only response from governments and business that can achieve this.
So what immediate three steps can you take in your business?
1) Set a net-zero target that recognises the climate emergency
2) Develop a comprehensive carbon footprint and plan to decarbonise rapidly
3) Don’t wait – implement your plan
 IPCC, 2021: Summary for Policymakers. In: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S. L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M. I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T. K. Maycock, T. Waterfield, O. Yelekçi, R. Yu and B. Zhou (eds.)]. Cambridge University Press. In Press, Figure SPM.8: Selected indicators of global climate change under the five illustrative scenarios used in this report
 Graphs from IPCC, 2021: Summary for Policymakers. In: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S. L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M. I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T. K. Maycock, T. Waterfield, Yelekçi, R. Yu and B. Zhou (eds.)]. Cambridge University Press. In Press, Figure SPM.8: Selected indicators of global climate change under the five illustrative scenarios used in this report
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