Skip to main content

Why climate 'uncertainty' is no excuse for doing nothing

By Richard Pancost, University of Bristol and Stephan Lewandowsky, University of Bristol

Former environment minister Owen Paterson has called for the UK to scrap its climate change targets. In a speech to the Global Warming Policy Foundation, he cited “considerable uncertainty” over the impact of carbon emissions on global warming, a line that was displayed prominently in coverage by the Telegraph and the Daily Mail.

Paterson is far from alone: climate change debate has been suffused with appeals to “uncertainty” to delay policy action. Who hasn’t heard politicians or media personalities use uncertainty associated with some aspects of climate change to claim that the science is “not settled”?

Over in the US, this sort of thinking pops up quite often in the opinion pages of The Wall Street Journal. Its most recent article, by Professor Judith Curry, concludes that the ostensibly slowed rate of recent warming gives us “more time to find ways to decarbonise the economy affordably.”

At first glance, avoiding interference with the global economy may seem advisable when there is uncertainty about the future rate of warming or the severity of its consequences.

So let’s do nothing. WSJ

But delaying action because the facts are presumed to be unreliable reflects a misunderstanding of the science of uncertainty. Simply because a crucial parameter such as the climate system’s sensitivity to greenhouse gas emissions is expressed as a range – for example, that under some emissions scenarios we will experience 2.6°C to 4.8ºC of global warming or 0.3 to 1.7 m of sea level rise by 2100 – does not mean that the underlying science is poorly understood. We are very confident that temperatures and sea levels will rise by a considerable amount.

Perhaps more importantly, just because some aspects of climate change are difficult to predict (will your county experience more intense floods in a warmer world, or will the floods occur down the road?) does not negate our wider understanding of the climate. We can’t yet predict the floods of the future but we do know that precipitation will be more intense because more water will be stored in the atmosphere on a warmer planet.

This idea of uncertainty might be embedded deeply within science but is no one’s friend and it should be minimised to the greatest extent possible. It is an impetus to mitigative action rather than a reason for complacency.

Uncertainty means greater risk

There are three key aspects of scientific uncertainty surrounding climate change projections that exacerbate rather than ameliorate the risks to our future.

First, uncertainty has an asymmetrical effect on many climatic quantities. For example, a quantity known as Earth system sensitivity, which tells us how much the planet warms for each doubling of atmospheric carbon dioxide concentration, has been estimated to be between 1.5°C to 4.5ºC. However, it is highly unlikely, given the well-established understanding of how carbon dioxide absorbs long-wave radiation, that this value can be below 1ºC. There is a possibility, however, that sensitivity could be higher than 4.5ºC. For fundamental mathematical reasons, the uncertainty favours greater, rather than smaller, climate impacts than a simple range suggests.

Second, the uncertainty in our projections makes adaptation to climate change more expensive and challenging. Suppose we need to build flood defences for a coastal English town. If we could forecast a 1m sea level rise by 2100 without any uncertainty, the town could confidently build flood barriers 1m higher than they are today. However, although sea levels are most likely to rise by about 1m, we’re really looking at a range between 0.3m and 1.7m. Therefore, flood defences must be at least 1.7m higher than today – 70cm higher than they could be in the absence of uncertainty. And as uncertainty increases, so does the required height of flood defences for non-negotiable mathematical reasons.

And the problem doesn’t end there, as there is further uncertainty in forecasts of rainfall occurrence, intensity and storm surges. This could ultimately mandate a 2 to 3m-high flood defence to stay on the safe side, even if the most likely prediction is for only a 1m sea-level rise. Even then, as most uncertainty ranges are for 95% confidence, there is a 5% chance that those walls would still be too low. Maybe a town is willing to accept a 5% chance of a breach, but a nuclear power station cannot to take such risks.

Finally, some global warming consequences are associated with deep, so-called systemic uncertainty. For example, the combined impact on coral reefs of warmer oceans, more acidic waters and coastal run-off that becomes more silt-choked from more intense rainfalls is very difficult to predict. But we do know, from decades of study of complex systems, that those deep uncertainties may camouflage particularly grave risks. This is particularly concerning given that more than 2.6 billion people depend on the oceans as their primary source of protein.

Similarly, warming of Arctic permafrost could promote the growth of CO2-sequestering plants, the release of warming-accelerating methane, or both. Warm worlds with very high levels of carbon dioxide did exist in the very distant past and these earlier worlds provide some insight into the response of the Earth system; however, we are accelerating into this new world at a rate that is unprecedented in Earth history, creating additional layers of complexity and uncertainty.

Uncertainty does not imply ignorance

Increasingly, arguments against climate mitigation are phrased as “I accept that humans are increasing CO2 levels and that this will cause some warming but climate is so complicated we cannot understand what the impacts of that warming will be.”

Well if we can’t be certain… Telegraph

This argument is incorrect – uncertainty does not imply ignorance. Indeed, whatever we don’t know mandates caution. No parent would argue “I accept that if my child kicks lions, this will irritate them, but a range of factors will dictate how the lions respond; therefore I will not stop my child from kicking lions.”

The deeper the uncertainty, the more greenhouse gas emissions should be perceived as a wild and poorly understood gamble. By extension, the only unequivocal tool for minimising climate change uncertainty is to decrease our greenhouse gas emissions.

The Conversation

Richard Pancost receives funding from the NERC, the EU and the Leverhulme Trust.

Stephan Lewandowsky receives funding from the Australian Research Council, the World University Network, and the Royal Society.

This article was originally published on The Conversation. Read the original article.

Comments

Popular posts from this blog

Bristol Future’s magical places: Sustainability through the eyes of the community

“What is science? Why do we do it?”. I ask these questions to my students a lot, in fact, I spend a lot of time asking myself the same thing.

And of course, as much as philosophy of science has thankfully graced us with a lot of scholars, academics and researchers who have discussed, and even provided answers to these questions, sometimes, when you are buried under piles of papers, staring at your screen for hours and hours on end, it doesn’t feel very science-y, does it?

 As a child I always imagined the scientist constantly surrounded by super cool things like the towers around Nicola Tesla, or Cousteau being surrounded by all those underwater wonders. Reality though, as it often does, may significantly differ from your early life expectations. I should have guessed that Ts and Cs would apply… Because there is nothing magnificent about looking for that one bug in your code that made your entire run plot the earth inside out and upside down, at least not for me.

I know for myself, I…

The Diamond Battery – your ideas for future energy generation

On Friday 25th November, at the Cabot Institute Annual Lecture, a new energy technology was unveiled that uses diamonds to generate electricity from nuclear waste. Researchers at the University of Bristol, led by Prof. Tom Scott, have created a prototype battery that incorporates radioactive Nickel-63 into a diamond, which is then able to generate a small electrical current.
Details of this technology can be found in our official press release here: http://www.bristol.ac.uk/news/2016/november/diamond-power.html.
Despite the low power of the batteries (relative to current technologies), they could have an exceptionally long lifespan, taking 5730 years to reach 50% battery power. Because of this, Professor Tom Scott explains:
“We envision these batteries to be used in situations where it is not feasible to charge or replace conventional batteries. Obvious applications would be in low-power electrical devices where long life of the energy source is needed, such as pacemakers, satellite…

Dadaism in Disaster Risk Reduction: Reflections against method

Reflections and introductions: A volta The volta is a poetic device, closely but not solely, associated with the Shakespearean sonnet, used to enact a dramatic change in thought or emotion. Concomitant with this theme is that March is a month with symbolic links to change and new life. The Romans famously preferred to initiate the most significant socio-political manoeuvres of the empire during the first month of their calendar, mensis Martius. A month that marked the oncoming of spring, the weakening of winter’s grip on the land and a time for new life.
The need for change Having very recently attended the March UKADR conference, organised by the Cabot Institute here in Bristol, I did so with some hope and anticipation. Hope and anticipation for displays and discussions that conscientiously touched upon this volta, this need for change in how we study the dynamics of natural hazards. The conference itself was very agreeable, it had great sandwiches, with much stimulating discussion …