History is full of people who predicted Armageddon. It never happened.
These false prophets of the past may comfort us when we hear scientists predicting catastrophes relating to climate change, biodiversity decline, food and water shortages; all of which are coming unless we change course from ‘business-as-usual’ (BAU). So many dire predictions have been proven to be wrong, won’t that also be true for climate change projections?
Some may also think, to misquote Shakespeare, that some scientists are ‘gilding the lily’ to simply get noticed or to get more research funding (two commonly proposed climate conspiracies).
And, after all, who can reliably predict the future?
With all predictions, we need to keep our brain cells on full alert and start by asking three sensible questions.
First, who is making these predictions? That is, are the person(s) well qualified to make such a statement? Is it in their area of expertise? And, what’s their track record from previous predictions?
Second, are these predictions ‘scientific’? That is, are they based on data, evidence and/or models that are verifiable, consistent, and replicable? And is there a well-understood, tested, and logically consistent scientific framework, with a falsifiable hypothesis, that supports the prediction(s)? And
Third, how credible are alternative predictions? That is, are there other alternative futures or predictions that are plausible and, equally or more likely?
These questions are not exhaustive but are sufficient to ‘falsify’ many, but not all, predictions.
So far, so good. But what if the ‘predictions’ are uncertain in terms of the timing and the magnitude of the impact(s) and are contingent on what happens in both the present and the future? In other words, how do we evaluate or test an uncertain prediction contingent on actions today and tomorrow? In such situations, it’s not about a single prediction. Rather, we are evaluating a series of projection(s) where each projection depends on what is assumed or estimated about key drivers that result in change, called a scenario.
For some projections there can be many possibilities (and sometimes thousands), each of which depends on a different scenario based on assumed or estimated drivers. For example, if we assume technological change is either slow, medium, or fast, we could have three different projections about the future depending on the assumed technological change (slow, medium, or fast). We may choose to give greater weight to one of the projections; for example, we think that rapid technological change is much more likely, but each projection is equally valid for the assumed scenario (slow, medium, or fast technological change).
In more complicated scenario projections, there may be multiple factors or drivers, not just one, assumed or estimated where, for each set of values for each driver, there is a separate scenario. Thus, choosing the preferred or the most likely projections out of the many possibilities requires judgement. When there are many projections (and even a single prediction), best practice would include the presentation of a distribution of outcomes from all possible projections with frequencies provided for the different outcomes.
In addition, an understanding of the robustness of the projections is valuable when deciding on what confidence we may have in the projections. Typically, the more robust (or less responsive) are the projected outcomes to large changes in the assumed or estimated possible scenarios (e.g., technological change), the more confident we should be as to the likely futures projected across the possible scenarios.
The judgement on projections is not whether they are true or not, which is the primary issue about an individual prediction about the future (eg, the world will end on 21st April 2025), but rather, do these projections provide insights or useful information about a possible future, contingent on a series of actions. For example, many different projections exist of what will happen to the Earth’s average surface temperature depending on what happens to future greenhouse gas emissions.
Projecting climate change
Global warming projections have been grouped into what are called Representative Concentration Pathways (RCPs) that depend on radiative forcing, a measure of planetary energy imbalance or how much is energy is coming from the sun in solar radiation versus the energy transmitted back into space in the form of infrared radiation, defined by Watts (W) per square metre (m2).
There are four core projections 8.5, 6, 4.5 and 2.6 W/m2 defined where the higher the W/m2 the greater is the energy imbalance relative to pre-industrial period (1850) because of a larger concentration of greenhouse gases in the atmosphere.
To better understand what climate change projections tell us and what the uncertainty is around such projections, we can review RCP 6.0 which is a high emissions and low mitigation scenario. For this scenario, atmospheric CO2 concentration rise to 670 ppm (parts per million) by 2100 from the current value of 420 ppm and its pre-industrial value of 280 ppm.
RCP 6.0 climate models project an increase in average surface (on land and sea combined) temperature of 2.20 C greater relative to 2020, or about 3.50 C higher than pre-industrial temperatures. Under this RCP 6.0 scenario, average surface temperatures may be up to 40 C greater than it was in 2000 by the year 2300; what can only be described as catastrophic climate change. In such a Hothouse Earth scenario, with this atmospheric CO2 concentration, there would eventually be no Amazon rainforest, no coral reefs, massive ice melt and sea-level rise, and parts of the world which are currently inhabited by hundreds of millions of people, possibly billions, would be unhabitable without artificial cooling.
In 2023 we cannot know the atmospheric concentration of CO2 by 2100 and, thus, the likely change in temperature. Nevertheless, we can provide a range of possible values based on current climate change policies, if these policies were to be maintained.
Based on the current trajectories, average surface temperature by 2100 would increase by about 2.80 C above pre-industrial levels with a 90% probability the range is from 2.10 C to 3.90 C. Notably, there is, at most, a 5% probability that the average surface temperature increase will only be less than 20 C.
None of these projections, alarming as they are, consider the possibility of ‘accelerated warming’ projected by some leading climate scientists that is contested by other climate scientists but is consistent with rapid warming in the oceans heat content. In this much worse case, average surface temperatures increase at 0.270C per decade due to ‘fast feedback’ between temperature change and energy imbalance, rather than the 1970-2010 warming rate of 0.180 C per decade.
The key point of the climate change projections is that what we do from this point forward in terms climate change policies, the levels of emissions, etc, will determine the speed and magnitude of climate change. While climate change policies between now and 2100 are highly uncertain, this does not mean there is any uncertainty about the eventual impact of CO2 emissions on atmospheric CO2 concentrations. Nor is the biggest uncertainty about the range of average surface temperature increases by 2100, or later, from higher carbon dioxide concentrations.
Rather, much of the uncertainty about what the future holds is about what we choose to do, collectively, in emissions reductions. That is, increasing the atmospheric concentration of greenhouse gases has already warmed our planet, and will continue to do so. This is a certainty. In other words, without a change in the current trajectory of greenhouse gas emissions to 2100, we will have a much warmer planet along with all that this entails including more intense and more frequent temperate extremes and storm events, sea-level rise, biodiversity loss, and so forth.
Net Zero and hot air
Given the sobering climate change projections we might think this would shock almostall of us into collective action and force our governments to change the current emissions trajectory. In fact, while many countries have agreed to ‘Net Zero by 2050’, greenhouse gas emissions continue to rise globally (including in 2022 in countries like Australia and Canada that have committed to substantial reductions in emissions by 2030).
Net Zero means that ‘negative’ emissions, such as from carbon sequestration from, say, growing forests, can offset actual emissions. If carbon sequestration at the scale required were possible by 2050, or earlier, Net Zero by 2050 could be feasible target. Unfortunately, it’s not. This’s because the required scale of carbon sequestration, either organically (eg, trees or algae) or via machines (eg, direct air capture technologies), and to safely store this carbon for a long time is massive. Notwithstanding the fact that the number of trees in the world continues to decline, there is simply not enough land available to grow, say, an additional one trillion trees and have sufficient food to feed the world. That is, much of the claimed potential scale of carbon sequestration from trees is simply ‘hot air’.
To understand the sequestration challenge, to sequester 10 Gigatons of carbon dioxide per year, currently less than a third of current annual global emissions from fossil fuels, would be at a scale that is orders of magnitude greater than the annual amount of oil extracted globally. It’s science fiction, at least over the next couple of decades, to expect negative emissions to be at sufficient scale to make a material difference to deliver net emissions by 2050. That is, Net Zero by 2050 can only happen if current emissions almost completely decline, as shown by the International Energy Agency.
What’s worse, ‘Net Zero by 2050’ is incentivizing a ‘burn now, pay later’ approach to the trajectory of greenhouse gas emissions because its sells the falsehood that negative emissions can take care of the climate change problem ‘down the road’.
So, what do we know, more or less, for sure?
First, the world is getting hotter, at a faster rate, and this will not be stopped unless we, collectively, bring our greenhouse emissions close to zero.
Second, maintaining or increasing greenhouse emissions will result in substantial temperature increases within coming decades that entails substantial costs and risks (possibly even catastrophic) to people, plants and animals from weather extremes and sea-level rise.
Third, carbon sequestration, over the coming few decades will only make, at best, a very marginal contribution to lowering atmospheric greenhouse gas concentrations.
Fourth, despite the rhetoric and a very real energy transition towards renewables, the world’s greenhouse gas emissions will continue to rise to at least 2030.
These are our future certainties under business-as-usual.
Why are we, as a species, so blind to the very large costs and risks of BAU?
Multiple explanations have been provided for our ‘lemming like’ behavior including ignorance (eg, we don’t know or we think we don’t know what will happen), selfishness (eg, we don’t care what happens in the future), short-termism (eg, we don’t want to pay today for a benefit sometime in the future), and blind optimism (eg, technology will fix it). Some may even believe that geoengineering may reverse the problems of climate change but this poses its own risks (and these are potentially enormous).
Paradoxically, some climate scientists may have contributed to an inadequate sense of urgency with claims, as late as 2023, of a ‘final warning’ that average surface warming can still be constrained to 1.50C. Pretending there is any chance of keeping warming to 1.50C to avoid people getting discouraged about mitigation diminishes trust with climate scientists when this possibility is well past. Such an approach that seeks to focus more on the ‘relative good news’, such as reporting more on climate change scenarios of less than 20C, and less on the more likely and higher temperature scenarios, is counterproductive.
In BAU we believe
Rearguard actions by those with most to lose (eg, fossil fuel companies) have also prevented meaningful policies to reduce greenhouse gas emissions through their large influence on decision-makers. Indeed, no more striking evidence of their impact on the climate change debate was the appointment as President of the United Nations’ climate conference in 2023, the 28th Conference of the Parties (COP), the head of a state oil company that pumps more than 2 million barrels of oil per day. And someone who claims that COP28 will “…keep [a temperature rise above pre-industrial levels of] 1.5C within reach…”.
Some of those who want to go slow on mitigation of greenhouse emissions (or stop altogether) have created false doubts and uncertainties among decision-makers and the general population about the effects of climate change. At the same time, some have resorted to ‘greenwashing’ to falsely burnish their credentials on mitigation.
In some countries, such as the United States, climate change propaganda has contributed to almost one in three Americans stating, in 2023, that either climate change is not too important (17%) or no action should be undertaken in terms of climate change (11%). Further, 14% of Americans believe there is no solid evidence that climate change is happening and, of these people, 67% have little or no trust in climate scientists.
Views that are contrary to well-documented scientific evidence, including indisputable measures of rising global temperatures, may be an extreme form of presentism when it can be hard, or impossible, to construct a future that is radically different to the present or past. It may also represent a form of ahistoricism where past events are seen to have little or no impact on the present and its equivalent, present actions have no impact on the future.
Whatever the explanation, the false belief in the safety of BAU is widespread, or in in a less extreme BAU with tweaks (eg, with carbon offsets) is alive and well. This belief is that, despite all the evidence, greenhouse gas emissions can continue to increase (or even peak) and the world can deliver Net Zero by 2050.
Either this view changes or our planet will continue rapidly warming. The choice is ours.