Climate consistency focus (or lack thereof...)

 Just two and a half months to go for finishing 2020, struggling to navigate a pandemic and its consequences, while still failing to gain awareness and develop social responsibility for tackling the climate and ecological crisis that sit at its origin.

Climate breakdown is not anymore a thread comfortably laying into the future (i.e. lending itself to the social irresponsibility of passing it to following generations), but is already happening in front of our eyes: The COVID pandemic, devastating wildfires all across the world (Australia, United States, Brazilian Amazon, artic tundra,…), floods, droughts, bleaching of coral reefs, agricultural yield reduction… All of them unfolding at higher rates than predicted by climate and earth system models. Last year was already 1.3C above pre-industrial levels, so when we speak about the huge socio-economic impacts of going beyond 1.5C global warming we are not talking about an hypothetic far away future, but about the reality of ours and next generation.

I am still surprised on how we insist on keep on fooling ourselves. The carbon budgets are a clear example of this. Here I discussed the climate consistency of the International Energy Agency (IEA) Sustainable Development Scenario from this perspective.

The carbon budget (CB) is a very useful yardstick to measure the climate consistency of how we plan to address the climate crisis. For any given year it states how much carbon dioxide we can still emit in order to keep global warming under a given threshold, and hence is the appropriate reference to check the climate consistency of transition roadmaps by comparing its cumulative emissions with the available carbon budgets.

The most recent consolidated reference from the Intergovernmental Panel in Climate Change (IPCC) is its 2018 Special Report on1.5C (SR1.5). In this report, the IPCC provided a significantly higher estimate of the remaining carbon budgets than the ones being used before, which were those from the IPCC fifth assessment report (AR5) from 2014. Here and here I discussed the very important differences between the carbon budgets in AR5 and SR1.5, as well as its potential implications. For 2021 we will have the sixth assessment report (AR6) from IPCC providing an update of the remaining carbon budget estimates as per the most recent climate simulations.

But let’s just take the current SR1.5 carbon budgets and come back to discus the social license to keep on fooling ourselves. Unfortunately, the IPCC SR1.5 had across its publication process several undefinitions that opened the door to different interpretations regarding the remaining carbon budgets (let’s hope the AR6 overcomes these issues), which subsequently led to develop policy transition roadmaps (like those from the International Energy Agency – IAE- and the International Renewable Energy Agency – IRENA) aligned with the higher boundary of the remaining carbon budgets estimates. These policy roadmaps inform policy-making in most countries, and due to the institutional and social inertia, lock us into transition pathways that can be inconsistent with climate breakdown. This could make us lose the tiny opportunity window still available to mitigate some of the consequences of climate breakdown.

Given the evidence of the already ongoing climate impacts (and the associated underestimate of our capacity to predict them), a basic precautionary principle should provide guidance on how to use the available information on the remaining carbon budgets with social responsibility, and to set the boundaries of the social license on how this is addressed.

Taking as basis the IPCC SR1.5 reported carbon budgets, minimum levels of social responsibility would require:  

•           Use average air temperature instead of mixed air and sea water temperature to characterize climate goals. Sea surface temperature is cooler than air temperature, and hence by mixing both we obtain a lower overall temperature (if we would mix air, water and ice temperature we would still obtain a lower average). Hence, using a mixed (air and sea water) temperature to define the goal for global warming (1.5C or 2C) is equivalent to implicitly admitting a higher warming of the air (and its associated impacts).
•           Including at least the very conservative estimates of Earth system feedbacks provided by IPCC. Earth system feedbacks are difficult to be modeled, and hence, most climate and earth system models do not include them. Yet, we are well aware of the fact that earth system feedbacks exist and that we are getting very close or perhaps already have surpassed the tipping points that trigger some of them. Our modeling abilities do not define reality, but rather the other way around: As we improve modeling skills and capacities, we better reproduce reality. The IPCC SR1.5 provides a very conservative estimate of earth system feedbacks (100 GtCO2 reduction in remaining carbon budgets), but yet this is not included in the reporting of the climate consistency of most transition roadmaps. Let’s hope the IPCC AR6 provides a more thorough evaluation of the likely impact for earth system feedbacks, but up till them at least the low recommendation from IPCC ASR1.5 should be included.
•           In 2019, after the publication of IPCC SR1.5C, one of the main databases for sea surface temperature was updated to correct for measurement errors, which has relevant implications on the remaining carbon budgets. The effect of any update in past measurement errors should be included into the carbon budgets we use to develop transition roadmaps and inform climate policy.

Factoring in these minimum levels of social responsibility in the use of carbon budgets, linear transition pathways provide a very convenient way to visualize and conceptualize the transition implications and its climate consistency. We already used here linear transition pathways to illustrate the climate urgency we are facing. The lineal evolution could seem too idealized and far from real evolutions, but the fact is that the transition roadmaps put forward by the International Renewable Energy Agency in its Global Renewables Outlook and the International Energy Agency in its World Energy Outlook are pretty linear in terms of the proposed emissions mitigation.

Figure-1 below presents different linear transition pathways starting in 2020 (and hence including the emissions reduction effect of the COVID-19 pandemic for 2020) and leading to zero emissions in different time horizons (without including negative emissions). As boundaries of these linear transition pathways, the transitions leading to cumulative emissions equal to the carbon budgets available in 2020 for 1.5C warming with 67% likelihood, 1.5C warming with 50% likelihood and 2C warming with 67% likelihood are also shown.

As we may appreciate, a transition consistent with having a 67% likelihood (it is worth pointing out that this is a rather low likelihood) of limiting global warming below 1.5C would require completing the transition within the following 5 years. Having a 50% likelihood (the flipping of a coin) to limit global warming to 1.5C would require completing the transition within a bit more than one decade. Having a 67% likelihood to limit global warming to 2C would require completing the transition by 2060.

To further document the impact of completing the transition in different time horizons, Figure-2 presents the cumulative emissions of linear transition roadmaps starting in 2020 and reaching zero emissions in different years with the available carbon budgets for different climate goals.

 

Figure-1: Historic evolution of total CO2 emissions up to 2019, linear transitions ending at different years, and limits associated to the 2020 carbon budgets for 1.5C@67%, 1.5C@50% and 2C@67%. 

  

Figure-2: cumulative emissions since 2020 of linear transitions ending at different years, compared with the available 2020 carbon budgets for 1.5C@67%, 1.5C@50% and 2C@67%.

Most the proposed transition roadmaps, and particularly those with the highest impact in crafting climate policy, reach zero emissions by 2060 – 2070, with the recent NZE2050 roadmap from IEA aiming at 2050 (although with a very poor documentation), and all include certain amount of negative emissions technologies. Yet, most of these transition roadmaps are put forward as Paris Agreement compatible or even aligned with a 1.5C global warming.