In this talk at the Edinburgh Climate Change Institute, Julian Caldecott warns of tipping points driven by global heating in the Arctic and other complex Earth systems. These systems have been under stress for decades, due to the heat-trapping effects of excess greenhouse gases. Using the case of the Arctic sea ice ‘death spiral’ since 1979, Julian explains how complex systems under this kind of stress tend to resist change before suddenly tipping into new forms. He then uses his knowledge of government climate aid programmes to show how being aware of mid-century deadlines can help us make better choices in mitigating climate change. Having a dated reference point would make it easier to calculate the true mitigation value of investments, thus helping to buy us time to build a safer and fairer world, one with peace with nature at its heart. But peace with nature needs ecosystem thinking, and this must quickly become normal if system change is to occur. Julian asks challenging questions about ‘business as usual’ climate aid, and offers new solutions in this most vital area of public policy.
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Some of the thinking in the talk is new and unorthodox. It treats Earth systems as complex and assumes that, like other complex systems, they can tip suddenly from one state to another after they have been under stress for a long time. Julian argues that just such a stress is the trapping of heat in the biosphere by greenhouse gases at a concentration in the air above 300 ppm CO2, which has been the case since about 1950. Its direct consequences include rising heat content of the world ocean and increasing global mean surface temperature (GMST). Its indirect consequences include declining polar sea ice volume, melting glaciers, marine and terrestrial heatwaves, weakening ocean currents and changing weather patterns that are often experienced as environmental chaos and usually described as climate change (CC).
The current 1.5 C goal, based on GMST, helps to focus public attention and mobilise action by governments. But it does not reflect the non-linear responses to be expected of a system as complex as the biosphere. The continuity of cause and effect over time, and the prospect of tipping points, challenge the realism of CC mitigation planning and investment assumptions. Improvements can be made by using an estimate of when Earth systems will, with current timing and heating trends, become irreversibly committed to transformational (‘tipping point’) change. This will pre-date the tipping point itself, so estimating when allows us to judge the effectiveness of CC mitigation investments in postponing it. Postponing tipping points is how we can buy ourselves time to make the changes needed for longer-term safety.
But such postponements may well become harder to do over time, as each system becomes steadily more inclined to transform itself. A relevant case is the ice-free Arctic Ocean, anticipated for September 2035 ± 5, which may already be unstoppable and could well drive a dangerous methane surge when it occurs. The mitigation value of delivering avoided net emissions would presumably decline in real terms as the commitment point is approached, either suddenly on its eve or more gradually in the preceding years. Uncertainties abound and call for precautionary thinking about the dates involved and the mitigation value of investments, including the unit value of mitigation returns on those investments. For these purposes, it is more realistic to reduce that value exponentially from now to the commitment point, rather than to assume a change from ‘valuable’ to ‘valueless’ the day before it.
Thus, a dated ‘deadline’ in mid century (2050 ± 10) might be chosen to represent the transformation commitment point of key Earth systems. This is based on the trajectory of change in sea ice minima in the Arctic Ocean, and on the rate and direction of change in other cryosphere (ice-world) and oceanic systems, and in major equatorial forest areas. Whatever the deadline chosen, precautionary investment plans would exponentially reduce the value of each expected mitigation unit as the deadline approaches. Such plans would therefore express all expected emission reductions not in tCO2e but in tCO2edmv, where ‘dmv’ stands for dated mitigation value. This would have the effect of valuing early net emission gains more highly than later ones. This is already in principle a common aim, but a standard metric would allow direct comparison of true cost-effectiveness between alternative investments in practice.
Julian tested the usefulness of this approach with data from projects funded by one EU member state in three developing countries, targeting: avoided deforestation; forest regrowth (also representing tree planting); wind farming (representing renewable energy, RE); and capacity building for economy-wide decarbonisation. Over 21 years with a constant 0.1 exponent used to depreciate mitigation value (such that 1 tCO2edmv in year 1 = 0.41 tCO2edmv in year 10 = 0.14 tCO2edmv in year 21), returns were estimated at 0.90 tCO2edmv/€ for capacity building, with least certainty; at 0.40 tCO2edmv/€ for avoided deforestation, with moderate certainty; at 0.05 tCO2edmv/€ for forest regeneration/planting, with moderate certainty; and at 0.01 tCO2edmv/€ for wind farming, with most certainty.
Among the cases with moderate to most certainty, the much higher mitigation returns from avoided deforestation than from RE and tree planting investments offer a key lesson to mitigation planners. Variation in the certainty of returns is an important factor in choosing the right mix of investments for each location, but so too are the varied co-benefits (biodiversity, adaptation, human rights, sustainable development, etc.) available from different investment strategies. And the biggest risk of all is that transformation commitment points in Earth systems cannot be postponed (or will not, due weak precaution and/or weak leadership).
This all suggests that a key starting point for justifying the expenditure of public mitigation funds lies the calculation of tCO2edmv/€. Once this is done, other factors such as expected co-benefits can be considered in detail. But the initial calculation would require an agreed deadline date (which could be moved by agreement later, if success is achieved), an agreed exponent for converting tCO2e into tCO2edmv, and attention to the comparative valuation of co-benefits for fine-tuning the justification of each investment.