Increasing swings in extreme weather are happening globally: it is clear that climate change is underway. If I was a gambling person, what odds would be favourable enough to place a bet that we would reach the global target of net-zero greenhouse gases by the end of the century?
Taking up a pen and paper I started carry out a back-of-the-envelope calculation to estimate the odds of reaching net-zero greenhouse gases by the end of the century. As Sir David Attenborough constantly reminds us, greenhouse gases are driving climate change which is a product of human activity. To get a handle on calculating our impact, I broke it into the following factors: population growth, technology development, climate policy, energy transition, and geopolitical stability.
The current global population is around 8 billion people. The best estimates give a spread of between 7 billion and 10 billion by the end the century. Therefore, I would give it a probability of about 50%, that the population will stabilise at around the current size and therefore its contribution to green house gases stabilise. Next is technology development which covers AI, biotechnology, green technology, and probably technology that we haven’t dreamed of yet. However, based on the speed of adopting new technology, which is always slower than we think because of high initial costs and the lack of skills to implement it, then it could take tens of years to stabile greenhouse gases, therefore I put it at a probability of 30%. Now for the one that is in the headlines most climate policy. The Paris Agreement set the global climate goals: limiting global warming to well below 2°C above industrial levels, preferably limiting the increase to 1.5°C and achieve net-zero global greenhouse gases in the second half of the 21st century. As of 2024, 140 countries have set net zero targets including: EU, UK, USA, Japan, and South Korea by 2050, China by 2060 and India by 2070. The current status is that the global greenhouse gases are still not declining fast enough to stay below 1.5°C, and it is currently estimated at 1.2°C, therefore it would be fair to conclude that climate policies are not working effectively, and therefore the probability of success is around 30%. Next is the energy transitions from oil based to clean sources such as electric sources of energy. Currently, only ~15% of global primary energy, that is, total energy used across all sectors, including heat and transport, comes from clean sources. Most applications such as transport, heating, and industry still rely heavily on fossil fuels. Although many businesses are giving out optimistic messages about the transition, I am not as hopeful that it will be fast enough to stabilise greenhouse gases, so I put the probability at 50%. Finally, geopolitical stability which is difficult to assess. If people are busy fighting for their survival then greenhouse gases and climate change isn’t a priority. There is more conflict in the world than reported in the media. For example, in 2023 about 14% of the world’s population lived within 5 km of a violent conflict. Therefore, I gave the probability of 30% that geopolitics will distract from work on reducing greenhouse gases and therefore it will not stabilise by the end of the century. Pulling all of the factors together to calculate the overall probability of reaching net-zero by the end of the century gives: \(0.5 \times 0.3 \times 0.3 \times 0.5 \times 0.3 = 0.00675\) or approximately 1 in 150 *chance that we will reach net zero by the end of the century - not good odds!.
Of course the above are all guesstimates supported by a lot of hand waving. But the key point is that there are many complex factors involved in reducing the greenhouse gases to net-zero. For example even if we were very optimistic about the success of each factor and recalculated e.g. \(0.9 \times 0.9 \times 0.9 \times 0.9 \times 0.9 = 0.59\) or which is only an evens change of reaching net zero. Global leadership needs to be made more accountable at reaching net-zero, honest about the success of reducing greenhouse gases to net zero, and put more effort into mitigating the effects of green house gases that are already built in to climate change. What bookmaker would give us favourable odds for achieving that?
* To convert from a probability to odds, divide the probability by one minus that probability. So if the probability is 0.00675, then the odds are 0.00675/(1-0.00675) or approximately ‘1 to 150’