The Precautionary Principle

Climate change scientists have estimated the impact of climate change on food, water, ecosystems, extreme weather events, and the risk of abrupt and irreversible changes (source) . In Figure 1, negative changes are coloured with an increasing intensity of red for each increase in global temperatures above pre-industrial levels. Neutral changes are coloured yellow, and positive changes are coloured green.

Figure 1: Impact of climate change

Reports by the IPCC are couched in terms of risk and probability because any field of science does not and cannot provide absolute certainty. All knowledge based on science is provisional. What distinguishes genuine science from pseudoscience is its willingness to allow evidence to confirm or challenge its theories. A strong pattern of climate science has developed over the last number of decades. With each increase in the understanding of our global climate systems, the more dire are the conclusions of climate scientists as to where our global climate system is currently heading due to insufficient action to reduce greenhouse gas emissions. Taleb and colleagues (2014) summarise the Precautionary Principle as follows:

“The precautionary principle (PP) states that if an action or policy has a suspected risk of causing severe harm to the public domain (affecting general health or the environment globally), the action should not be taken in the absence of scientific near-certainty about its safety. Under these conditions, the burden of proof about absence of harm falls on those proposing an action, not those opposing it.”

Figure 2: Climate change forms an existential threat

The action of burning fossil fuels accompanied by greenhouse gas emissions to the atmosphere falls well within the category of applying the Precautionary Principle because failure to cease burning fossil fuels sufficiently quickly would result in an existential threat to all forms of life on Earth. When confronted by a lack of absolute certainty, and especially when risks involve existential threats, the Precautionary Principle as adopted by the United Nations must be abided by all nations, including New Zealand.

There are some who advocate deliberately seeding the atmosphere with SO2 so as to reverse global warming. Such an action could have dire consequences and should be contemplated only if all other climate mitigation options are exhausted. The precautionary principle dictates that the best action to mitigate the impact of climate change is to reduce our CO2 emissions.

We have a choice to make here for the sake of the survival of our own species and all other species on Earth. The choice we have is either a Hothouse Earth where we are currently heading or a Stabilized Earth. Lack of absolute certainty must not be allowed to be an excuse for any further delays in necessary action to mitigate the impact of climate change. The longer we delay action, the greater is the risk of a Hothouse Earth.

Climate change has been globally acknowledged and accepted as being an existential threat to humans and other life forms. Virtually every nation in the world agreed to work together to achieve net zero greenhouse gas emissions by 2050 in the 2015 Paris Agreement. The 2015 Paris Agreement was adopted by a resolution of the United Nations General Assembly.

Figure 3: Adoption of the Paris Agreement

The target of the 2015 Paris Agreement was to hold the global average temperature to well below 2°C above pre-industrial levels and to pursue efforts to limit the temperature increases to 1.5°C. Reductions would be undertaken in accordance with the best science and on the basis of equity. It was recognised that the less-developed nations would require financial assistance from the well-developed nations. The 2015 Paris Agreement recognised that business-as-usual emissions of greenhouse gases must be curbed. Adoption of a carbon budget was agreed upon. The budget is an annual reducing budget, the total size of which is represented by the area under the curve of projected reductions in carbon dioxide emissions as shown in Figure 4 below. In 2015, the carbon budget targeted to decline to net zero by 2050 was deemed to be sufficient mitigation.

Figure 4: Carbon budget required to mitigate the impact of climate change

Subsequent research by the IPCC has revised the urgency to reduce greenhouse gas emissions. The IPCC AR6 Report of 2021 indicates that the remaining carbon budget required to remain within 1.5° C of global warming with 66% probability is 400 billion tonnes of CO2 and 300 billion tonnes with 83% probability. On a 400 billion tonnes carbon budget, an average country share of the global carbon budget would run out in 9 years. In other words, we need to target zero carbon emissions by 2030 and not by 2050. For a high polluting country such as the United Kingdom, its share of the carbon budget would run out in 3 years at current rates of use (Chancel 2021)
Any level of greenhouse gas emissions accumulates in the atmosphere. Despite international agreements to adopt zero carbon budgets with declining annual levels of greenhouse gas emissions, global annual greenhouse gas emissions have started to increase again after a brief decline due to reduced economic during the peak of our recent COVID pandemic (https://www.co2.earth). Business-as-usual growth in the use of fossil fuels for energy must not continue if we are to mitigate the impact of human induced climate change.

Climate Action Tracker recently published a November 2024 update. In November 2024, climate warming was 1.44°C above pre-industrial levels and 2024 was the warmest year since 1880 (Climate Action Tracker). In a best-case optimistic scenario which assumes full implementation of all announced targets, our climate would be heading towards 1.9°C and as high as 2.4°C above pre-industrial levels by 2100. More commitment is required to keep under 1.5°C.

Figure 5: Warming Projections Global Update November 2024 (Insert)

In a real-world action scenario based on current policies, our climate would be heading towards 2.7°C and as high as 3.4°C above pre-industrial levels by 2100. This scenario represents a severe existential threat to all life forms on Earth. Urgent action is now more than ever necessary. Climate change is not going to go away, and the longer we delay in reducing our greenhouse gas emissions, the more greenhouse gases accumulate in the atmosphere and the more dire the impact of climate change becomes.

In order to avoid the prospect of a hot-house Earth, we need to reduce and eliminate our use of fossil fuels as an energy source. But we are totally reliant on high grade energy and materials for our survival. We have a choice here.

Unless we are prepared to adopt a hunter-gatherer existence, we have no choice but to transition from fossil fuels to high grade renewable energy and infrastructure.

Figure 6: Our energy choice

We have a choice to make here for the sake of the survival of our own species and all other species on Earth.

The choice we have is either a Hothouse Earth where we are currently heading or a Stabilized Earth.

Lack of absolute certainty must not be allowed to be an excuse for any further delays in necessary action to mitigate the impact of climate change.

The longer we delay action, the greater is the risk of a Hothouse Earth.

In order to avoid the prospect of a hot-house Earth, we need to reduce and eliminate our use of fossil fuels as an energy source