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Balancing climate and development goals

Lei Duan, Juan Moreno-Cruz, and Ken Caldeira · Environmental Research Letters 15, 124057 · 2020

Key finding. If every country begins decarbonizing in 2020 at 2% per year, the world warms about 2.0 °C relative to pre-industrial; if countries instead begin only once per-capita GDP exceeds $10,000, less than 0.3 °C of additional warming results — despite more than half the world's population currently living in countries below that income threshold.

A line plot of additional global temperature increase in degrees Celsius against the cumulative percentage of world population, with five curves for decarbonization rates of 0, 1, 2, 4, and 8 per cent per year. The curves stay near zero across the poorest 40 per cent of the world's population, step up to about 0.4 °C at the point marking a per-capita income of 10,000 dollars per year covering roughly 55 per cent of people, and reach about 1.0 °C at the 20,000 dollar mark near 85 per cent.
Additional warming attributable to letting countries develop before they decarbonize, plotted cumulatively by population. More than half the world's population can be exempted for well under half a degree, because emissions are concentrated among the wealthy rather than the numerous. Figure 3 from Duan et al. (2020), Environmental Research Letters 15, 124057. Reproduced under CC BY 4.0. Extracted from the published PDF and resized for web display.

What question did this research address?

The richest countries face the challenge of decarbonizing their energy systems. The poorest face the challenge of providing energy services at all. Those are different problems, and it is not obvious that the same policy serves both.

This paper asked a bounded version of the question: what would the climate consequences be if only richer countries focused on decarbonization, and poorer countries focused on providing energy services until they became wealthy enough to switch?

What did we find?

The scenarios let CO2 emissions follow a historical trend and then decline once a country reaches a specified income level, with a central assumption that decarbonization proceeds at 2 per cent per year once it starts.

With all countries starting in 2020, expected warming is about 2.0 °C above pre-industrial levels.

Tying the start of decarbonization to a per-capita GDP threshold of $10,000 adds less than 0.3 °C of warming on top of that.

The reason the penalty is small is that emissions are concentrated among the wealthy. Although over half the world's population lives below the threshold, their direct CO2 emissions while they remain poor are a small share of the global total.

Why does it matter?

The result dissolves an apparent conflict. Climate goals and development goals are often presented as competing claims on the same budget, but on these numbers allowing poorer countries to develop first costs remarkably little warming.

It also relocates the obligation. If the climate consequence of poor countries developing is small, then the emissions that determine the outcome belong to wealthy countries, and the argument that global mitigation requires universal simultaneous action does not hold.

Citation

Lei Duan, Juan Moreno-Cruz, and Ken Caldeira (2020). Balancing climate and development goals. Environmental Research Letters 15, 124057.

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