A note of caution

I am truly astonished. Doubly astonished. There is the original paper in Nature magazine, Emissions – the ‘business as usual’ story is misleading by Zeke Hausfather & Glen P. Peters. This is what classical empiricists have been saying all along regarding AGW. Saying and then being pilloried as climate-deniers or science-deniers. It is a topsy-turvy world where those demanding the rigor of science are being attacked as science-deniers.

From the article.

Stop using the worst-case scenario for climate warming as the most likely outcome — more-realistic baselines make for better policy.

More than a decade ago, climate scientists and energy modellers made a choice about how to describe the effects of emissions on Earth’s future climate. That choice has had unintended consequences which today are hotly debated. With the Sixth Assessment Report (AR6) from the Intergovernmental Panel on Climate Change (IPCC) moving into its final stages in 2020, there is now a rare opportunity to reboot.

In the lead-up to the 2014 IPCC Fifth Assessment Report (AR5), researchers developed four scenarios for what might happen to greenhouse-gas emissions and climate warming by 2100. They gave these scenarios a catchy title: Representative Concentration Pathways (RCPs)1. One describes a world in which global warming is kept well below 2 °C relative to pre-industrial temperatures (as nations later pledged to do under the Paris climate agreement in 2015); it is called RCP2.6. Another paints a dystopian future that is fossil-fuel intensive and excludes any climate mitigation policies, leading to nearly 5 °C of warming by the end of the century2,3. That one is named RCP8.5.

RCP8.5 was intended to explore an unlikely high-risk future2. But it has been widely used by some experts, policymakers and the media as something else entirely: as a likely ‘business as usual’ outcome. A sizeable portion of the literature on climate impacts refers to RCP8.5 as business as usual, implying that it is probable in the absence of stringent climate mitigation. The media then often amplifies this message, sometimes without communicating the nuances. This results in further confusion regarding probable emissions outcomes, because many climate researchers are not familiar with the details of these scenarios in the energy-modelling literature.

This is particularly problematic when the worst-case scenario is contrasted with the most optimistic one, especially in high-profile scholarly work. This includes studies by the IPCC, such as AR5 and last year’s special report on the impact of climate change on the ocean and cryosphere4. The focus becomes the extremes, rather than the multitude of more likely pathways in between.

Happily — and that’s a word we climatologists rarely get to use — the world imagined in RCP8.5 is one that, in our view, becomes increasingly implausible with every passing year5. Emission pathways to get to RCP8.5 generally require an unprecedented fivefold increase in coal use by the end of the century, an amount larger than some estimates of recoverable coal reserves6. It is thought that global coal use peaked in 2013, and although increases are still possible, many energy forecasts expect it to flatline over the next few decades7. Furthermore, the falling cost of clean energy sources is a trend that is unlikely to reverse, even in the absence of new climate policies7.

My position has been that we are attempting, with climate, to model a grossly complex system of loose and tightly coupled complex subsystems with very imprecise and largely incomplete data frequently compounded by motivated and/or careless human error.

The models themselves have built-in biases which are hard to disentangle.

Explicitly, climate change is constant, it consists of micro-, local, and regional climate change as well as global, it entails subsystems of complexity which we poorly understand (ocean heat absorption, ocean currents, cloud cover, solar cycles, land use impact, etc.) and chemistry effects which are poorly mapped between lab and experience.

Because of poor, incomplete, and imprecise data, we have a difficult time measuring the actual global temperature history much less monitoring it even today. On an uncertain data base, we layer a poorly validated and extremely sensitive complex modeling, which produces outcomes most people do not comprehend.

That has been pretty much the classical empiricist case and at last someone seems to be making it in Nature. Not quite as forcefully, but there it is. Astonishing that it exists at all.

No, the world is not going to end in twelve years. No, our major cities are not going to be under water. No, we probably can probably only affect things at the margin after taking into account the existing natural processes.

Which doesn't mean we should do nothing. We should seek cleaner energy sources, we should seek ways to reduce resource consumption (without degrading human well-being). But no, we don't need to adopt central planning to do this within a twelve year window. Hitchhiker's Guide to the Galaxy advice remains true. Don't Panic!

Experiment, test, refine, improve, and most of all let free people create imaginative new solutions adopted at their own volition.

Most astonishing beyond the paper is that it is reported in that bastion of technocratic central planning ideology, the BBC. Climate change: Worst emissions scenario 'misleading' by Matt McGrath.

Does this mean that our projections about future temperature rises are wrong?
Not necessarily.

This new work questions the chances of very high future emissions because renewable energy is now much cheaper, and competing with coal.

So rather than a world that warms by 6C, it should mean that the world will warm by around 3C based on current policies that countries have signed up to.

The melting of Arctic ice could speed up the warming of the world
However, the authors are at pains to point out that the lower temperatures aren't guaranteed.

Still not really engaging with the underlying reality. These are human-crafted statistical models subject to subtle biases and mistaken assumptions. What is the temperature going to be a hundred years from now? A thousand? Ten thousand? Well it will be different from today even were there no people because of differences in solar cycle and other natural systemic variations.

How much warmer/colder might it be due to human actions? That's the question and about which we are still spit-balling. We have a hard enough time measuring the past and forecasting the natural future. Differentiating the possible human contribution is excruciating and we are certainly not there yet.

The BBC and Nature are to be commended on finally introducing some modicum of empirical caution to the hysteria of the past decade.

Strikingly, I have seen nothing in the American press about the paper and the caution. Perhaps it is just buried by the impeachment and the Iowa debacle and other pressing social reporting. Or perhaps the AGW religion in the mass media is more resistant to blasphemy.

Still, fantastic to see the caution in Nature.