Global warming: Why focusing on 1.5C is flawed 

Limiting global heating to 1.5C will not make the world safe. Instead, we should decide on the tipping points we wish to avoid, write Henry Throp and Laurie Laybourn.

The World Today
Published 29 September 2023 Updated 6 November 2023 3 minute READ

Supercharged by record carbon emissions and an emergent El Niño, the world temporarily passed 1.5C of global heating this year. This doesn’t mean the goal to limit the rise in average global temperature to within 1.5C above the pre-industrial era average set by the Paris Agreement has been lost. That only happens when the temperature stays consistently above the 1.5C limit.

It does, however, mean that the reductions in emissions needed to meet 1.5C are now precipitously steep. This has led to a growing chorus of commentators saying that limiting the global temperature rise to 1.5C is no longer possible. For example, The Economist in 2022, in the run-up to COP27, ran an editorial urging the world to ‘say goodbye to 1.5C’.

Such views have been met with a forceful pushback, including from the head of the UN’s weather agency, who has said that the loss of 1.5C is ‘factually incorrect, and politically it is very wrong … the fact is that the chances of 1.5C are narrowing, but it is still achievable’. This debate will continue with force at COP28 in the United Arab Emirates from the end of November.

It is still physically possible to limit global temperature rises to 1.5C. The UN’s climate science body, the Intergovernmental Panel on Climate Change, says that global heating has reached around 1.1C  and climate science tells us that when emissions stop, the temperature rise will begin to stabilize.

In reality, the debate over whether 1.5C is or isn’t physically possible hides a more fundamental question over the future of climate action. Instead, the debate is about what changes we can and should realize to tackle climate change.

The real debate

While setting an ambition to limit climate change to 1.5C has provided a clearer focus for climate politics, there is little consensus on the specific policies that can then credibly deliver that target. The scientific community is clear that climate action must be faster and more fundamental than is currently being delivered or even considered by governments and companies.

For example, the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services has concluded that only a ‘fundamental, system-wide reorganization across technological, economic and social factors, including paradigms, goals and values’ can avoid the worst. In practice, this would mean the rapid phasing down of the fossil fuel industry and an equally speedy increase in measures to manage demand for energy and other environmental harms.

Major crop-growing regions could be hit simultaneously by climate shocks, causing a global food crisis

Some of those saying it is not possible to limit warming to 1.5C do not think such changes are politically feasible. Others might simply not want these changes to happen, particularly if they disrupt or even destroy business models. This attitude sits behind the fossil fuel industries’ well-publicised efforts to subvert politics and delay emissions reductions, which has harmed chances of limiting warming to 1.5C.

Yet to exceed 1.5C will entail deadly, if not catastrophic, risks. These include crises that afflict entire societies and economic systems, such as the growing chance that major crop-growing regions – ‘breadbaskets’ – could be hit simultaneously by climate shocks, causing a global food crisis.

Perhaps most worryingly, exceeding 1.5C would put the world deep into the zone of risk of triggering climate tipping points. These are abrupt events in which parts of the natural world break down, stressed beyond their limit by climate change and biodiversity loss.

‘Derailment risk’

The reality is that, without global emergency action to reduce emissions, 1.5C of warming will probably be breached sometime in the 2030s. Its political lifespan is likely to be shorter than its scientific one, as the increasing frequency of temporary breaches lends credence to those voices saying that 1.5C is lost.

If the world heads above 1.5C, many of the risks that have been warned of will begin to manifest across the world. Mounting chaos will draw a political response. On the one hand, opportunities will grow to make the connection between worsening impacts and the imperative for rapid decarbonization that stems the flow of chaos. On the other, the severe effects of that chaos will create huge demands on emergency responses and protection measures.

This could present a tension between demands on adaptation and the necessity for accelerating emissions reductions. This has been termed ‘derailment risk’: the escalating symptoms of climate change could get in the way of tackling its root causes. It is imperative that this tension is broken.

A different direction

There is an alternative trajectory. It first requires us to recognize the flaws of 1.5C as the global focal point for action. While providing a far less deadly limit to temperature rises, stopping at 1.5C will not make the world safe. Current temperature rises are already having devastating and unequal impacts across the globe.

Each degree in warming is important, but those that trigger tipping points are more important 

Instead, targets should focus more on the specific threats we wish to avoid. These things include the triggering of tipping points, the failure of breadbaskets and ever more grotesque climate injustices. All these things are still possible below 1.5C.

Falling back on a higher temperature goal, such as 2C, would be a mistake because of the risks we now know lurk around 1.5C. Likewise, the alternative narrative that ‘every degree counts’ is still imprecise. Each degree in warming is important, but those that trigger tipping points are more important than others.

Instead, we should aim to reduce the rate of temperature change to zero and, ultimately, to a negative rate of change, so that global temperature levels are brought down. This will require us to rapidly reach net zero greenhouse gas emissions, then seek further reductions to achieve net negative, where more emissions are being drawn out of the atmosphere than enter it.

A huge gamble

This cannot happen if the net element of emissions reductions is used to justify continued use of fossil fuels with the expectation that those emissions are offset at some point in the future by vast amounts of as-yet unproved carbon capture storage technologies. This expectation currently underpins the actions of  many governments and companies. It is a huge gamble.

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We must be similarly sceptical of solar geo-engineering, such as the injection of sulphur particles into the atmosphere to reflect sunlight – these technologies are unproved and dangerous. The false promises of geo-engineering will be on show at COP28, where we will see the tussle over whether 1.5C is dead or alive grow further.

Instead, these crucial global moments should be used to agree on strategies that better confront the dangerous reality and spur the courage and cooperation needed to realize rapid, equitable climate action.