We Need to Stop Pretending we can Limit Global Warming to 1.5°C
The era of a safe climate is over – now we must confront the reality that we will overshoot and adapt, says top earth system scientist James Dyke
We are not going to limit global warming to 1.5°C. This means we will soon be entering a much warmer and more dangerous world.
The threshold of 1.5°C was the highest ambition of the landmark 2015 Paris Agreement. It was arrived at by a realisation that warming beyond this temperature would produce intolerable suffering to those most exposed to global warming.
So what can we make of politicians who continue to argue that ‘1.5°C is still alive’? Are they misinformed or are they simply lying?
I believe many are in denial about the types of solutions the climate crisis demands. Rather than do the – admittedly – very difficult political work of eking out our supplies of fossil fuels while accelerating a just transition to post-carbon societies, politicians are going all out on technological salvation. This is a new form of climate denial, which involves imagining large-scale carbon dioxide removal that will clean up the carbon pollution that we continue to pump into the atmosphere.
While it may seem much safer to stick to the script and say that it is still physically possible to limit warming to no more than 1.5°C, while pointing out that the scale of change demands much more political will, I believe that this can no longer be a credible response to the climate crisis.
We have warmed the climate by 1.2°C since pre-industrial periods. If emissions stay flat at current levels, then in around nine years the carbon budget for 1.5°C will be exhausted. And, of course, emissions are not flat – they are surging. 2021 saw the second-largest annual increase ever recorded, driven by the rebound in economic activity after Coronavirus lockdowns. We did not ‘build back better’.
The clock has been stuck at five minutes to midnight for decades. Alarms have been continuing to sound. There are only so many times you can hit the snooze button.
Concluding that 1.5°C is over is not a fringe view within climate science.
A 2021 survey by the science journal Nature found that a majority of world-leading climate scientists believe that we are heading towards a catastrophic 3°C of warming by the end of the century. Only 4% surveyed said they thought limiting warming to 1.5°C was likely.
While climate scientists are probably not best placed to comment on the possibility of the social, economic and political transformations required for 1.5°C, they are eminently placed to determine whether plans to limit warming to 1.5°C are plausible. This is because such plans now almost always rely on removing vast amounts of carbon dioxide from the Earth’s atmosphere and burying it in the Earth’s crust, oceans, soil and biomass.
The most optimistic scenario the UN’s Intergovernmental Panel on Climate Change (IPCC) can now offer is overshoot – a situation where temperatures will exceed 1.5°C with planetary-scale carbon removal technologies dragging temperatures back down by the end of the century.
This is now effectively baked in to all net zero policies that attempt to douse the looming threats of global warming with a firehose of acronyms – BECCS (Bioenergy Carbon Capture and Storage), DAC (Direct Air Capture), CCUS (Carbon Capture Utilisation and Storage). But there are serious scientific as well as economic and moral problems with these approaches.
BECCS was once seen as the most promising climate saviour technology. The approach was to essentially burn trees instead of coal in power stations, then capture the carbon dioxide before it left the chimneys, and pump that captured carbon into deep underground storage sites. If the carbon stayed there, this would amount to a flow of carbon dioxide out of the atmosphere. That’s because, as trees grow, they absorb carbon. Capturing and storing the carbon would be a clever way of both producing electricity and reducing the total concentrations of carbon dioxide in the atmosphere.
But the scale of BECC being imagined would require the planting of fast-growing trees up to an area twice the size of India. This could devastate biodiversity, threaten people’s food and water security, and displace them from their lands.
There is also the challenge of how captured carbon can be safely stored. While the idea sounds simple – pumping concentrated carbon dioxide underground into porous rock – getting it to stay there and in large volumes is not trivial.
Pilot carbon storage project have repeatedly missed targets. In principle, there should be space to store hundreds of billions of tonnes of carbon dioxide within rocks. Today we are able to store maybe hundreds of thousands of tonnes. The geoscience and engineering challenges required to scale that up to gigaton storage are staggering.
That’s why high-tech approaches such as DAC do not represent any breakthrough. They do avoid the problems of needing huge amounts of land and water but still face the issue of how to keep carbon dioxide underground essentially forever. And they come at high energy costs – some 2,000 kw/hours required to capture one tonne of carbon dioxide. We need every watt generated by solar, wind and other renewables to replace the coal, oil, and gas that still supply 80% of humanity’s total energy need. In that context, DAC is a very expensive distraction.
The response to these limitations is that BECCS or DAC are really just placeholders for some future solution – and perhaps some breakthrough technology will emerge. But will it emerge in time, at scale, and at feasible economic costs?
Some studies estimate that we could be spending trillions of dollars in a desperate attempt to drag temperatures back down to 1.5°C. Will rich, industrialised nations spend that much cash when they cannot even forgo the modest economic impact of not putting the carbon in the atmosphere in the first place?
The response to such questions is that we will be able to afford these eye-watering costs because, in the future, our economies will be so much larger. This can produce the Kafkaesque argument that we must continue to emit carbon dioxide into the atmosphere, because we need to use fossil fuels to maintain economic growth, in order to be able to afford the costs of removing carbon dioxide from the atmosphere.
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Breaking the Silence
If it is now abundantly clear that we are going to exceed 1.5°C, why is there not a deafening shout from academia, activists and politicians about this? I believe that much of the hesitancy stems from being afraid of what comes next.
If we really are destined to pass 1.5°C, what difference does calling the situation early make? Couldn’t it be counter-productive and play into the hands of those who see climate change as only a risk to their profits? Does this mean that we should fall back to 2°C? Or just give up? Would admitting the failures to act in time mean that we are doomed to climate collapse and all is lost?
Our first responsibility must be to tell the truth – as far as we can divine it. To not do so because we fear the consequences is not a defensible position.
When we do pass 1.5°C, and wider society learns that we knew this was very likely to happen but did not clearly say so, we face a crisis of trust. Most academics continue to insist that it is still – barely – physically possible to limit warming to no more than 1.5°C. There are strong incentives to stay behind the invisible line that separates academia from wider social and political concerns, and so to not take a clear position about this.
But we need to clearly acknowledge now that warming will exceed 1.5°C because we are losing vital reaction time by entertaining fantastic scenarios. The sooner we get real about our current situation and what it demands, the better.
We also need to go beyond saying the obvious – that every degree of warming matters – and do the much harder job of understanding why rapid decarbonisation has thus far been so difficult and get around this. We must acknowledge that vastly more effort is needed to protect those most exposed to existing and future global warming.
This does not mean abandoning the Paris Agreement or tearing up net zero policies and climate legislation. It doesn’t mean giving up on reducing greenhouse gas emissions and instead pouring all available resources into adaptation. And it does not mean we are all doomed.
No Safe Overshoot
The world will not end when we warm beyond 1.5°C. What will happen is that more people will suffer and die along with countless other species we share the biosphere with. Some tipping elements in the climate system may be activated such as the disintegration of Greenland and Western Antarctic Ice Sheets.
The good news is that these will take many centuries to completely melt and so the tens of metres of sea level rise expected will happen very slowly.
The bad news is that the more research done on these tipping elements and how they interact, the more dangerous exceeding 1.5°C and 2°C appears.
Our understanding of how the complex Earth system responds to our multiple fronts of assault is far from complete.
The assumption that we can safely overshoot, then recover temperatures back down by the end of the century, is seriously misguided. Alas, this is the story that we are telling ourselves. It allows us to imagine the world continuing essentially unchanged. It also happens to be a story that does not seriously threaten the wealth and power that centuries of fossil fuel use has concentrated into a tiny fraction of humanity.
What is so maddening is that there are alternatives. There is an abundance of theory and arguments that could lead the way. The latest IPCC report had an entire section that doesn’t propose technofixes but instead explores how energy demand could be managed to ensure that everyone has enough to thrive while ensuring the biosphere doesn’t die.
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Some of these ideas sound radical, but they are much more grounded in reality than breathless promises of wonderous machines. Some of it could be described as common sense. One way to rapidly reduce the greenhouse gases that are generated from energy and material consumption is to reduce energy and material consumption. Unfortunately, such a view is tantamount to heresy in climate policy. Growth must be maintained.
The safest, sanest thing to do right now is to stop using fossil fuels as quickly as we can. This will limit warming to as near to 1.5°C as possible. At the same time we need massive investment in adaptation to protect those most vulnerable. There are already enough resources, technology and knowledge to go around – the challenge, of course, is how these are distributed and used to protect people and the biosphere.
We should also urgently explore how natural carbon sinks could be restored and enhanced such as reforestation. This has the potential to drag temperatures back down. But the timescales involved here could be centuries before we are able to return to 1.5°C. We need to understand that it is very likely that we will have to live with whatever warming we produce this century.
Rather than collapse into despair, getting real about 1.5°C should mean we are able to hold open a space of grounded, realistic optimism. What we do matters – our actions count and this becomes more, not less, important once we realise how grave our situation is.
Sometimes we only notice a sound when it stops. The time has come to turn off the alarms, to fully wake up, and listen to the silence it creates. This silence is full of possibilities. We cannot wish away decades of slumber. But we can take an unflinching look into our future and now, finally, do the work to shape it.
Dr James G Dyke is Associate Professor in Earth System Science and assistant director of the Global Systems Institute at the University of Exeter
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