The world is going to miss the totemic 1.5°C climate target

Three strikes and you’re out is a pretty good rule. And the politicians and negotiators attending the Paris climate summit, “cop21”, in December 2015 were facing their third strike. Their first and second attempts to bind the world into a meaningful pact that would control greenhouse-gas emissions—in Kyoto in 1997 and in Copenhagen in 2009—had failed. If on their third time at bat they could do no better, the world was cooked.

There was thus immense pressure on all at the conference to achieve a robust outcome. And a group of politicians and policymakers representing some of the world’s poorest countries had a very specific and controversial requirement for what it should contain. James Fletcher, of St Lucia, recalls that he and his fellow representatives of Caribbean states were “very clear in our minds that 1.5°C was a red-line item. It was one of the things that we said kind of silently: that we would be prepared to walk away from the negotiations if there was a sign we would not be getting a reference to 1.5°C in the Paris agreement.

”Many island states had the same red line. Their reasoning was simple. For a country like the Maldives, with more than 80% of its land rising less than one metre above sea level, more than 1.5°C (2.7°F) of global warming would see most of its sovereign territory disappear. Some continental countries which felt themselves at particular risk, or felt a particularly strong sense of solidarity, embraced the cause too. Third-strike make-or-break Paris was the perfect place to take a stand.

In the years since they originally signed the un Framework Convention on Climate Change (unfccc), which was negotiated in 1992, the countries of the world had not committed themselves to a temperature target. Part of what mattered about Paris was that they were finally going to do so. The limit most countries, including all the big emitters, had in mind was 2°C. It had become accepted, without any compelling evidence, as a boundary below which global warming, while regrettable, did not constitute “dangerous anthropogenic interference with the climate system”—the thing that the unfccc’s signatories were pledged to avoid. It was also much better than what then seemed on the cards if the world did not act; business-as-usual projections showed temperatures rising 3.5°C or more above the pre-industrial baseline.

Given the predisposition against it by all the large countries, the 1.5 brigade’s tough stance managed to get their ideas further than most observers had expected. The text gavelled into history after two weeks of negotiations went beyond a simple 2°C goal, speaking instead of “Holding the increase in the global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C.” Cue cheers and hugging. “It was one of the rare victories of the poor, vulnerable countries in this arena,” says Saleemul Huq, a veteran of climate negotiations from Bangladesh.

Wishing they were there

In the years since Paris, the 1.5°C target went from something to be pursued to something totemised. A stretch goal has been widely treated as a paramount one.

The process was strengthened by a report published by the Intergovernmental Panel on Climate Change (ipcc) in 2018 which compared what the world might expect at 1.5°C with what 2°C would look like. Even as temperatures crept up by just half a degree, impacts and risks became worse in every possible domain, from fisheries to floods, droughts to decimated ecosystems. In a 2°C world, some 420m additional people would be exposed to record heat, millions more people would have their livelihoods wiped away by higher seas. An ice-free Arctic would be expected once a decade rather than once a century.

As well as looking at impacts, the 2018 report also weighed in on emission pathways. Its conclusions formalised the idea that, in order for the 1.5°C target to be met, net emissions needed to zero out around the middle of the century. The “Net-zero by 2050” mantra galvanised politicians and businesses as well as activists.In 2019 the Science Based Targets initiative, a non-profit project that provides the corporate and financial sectors with guidance and technical assistance on their plans for climate action, launched the “Business ambition for 1.5°C” campaign with 28 early adopters. At last check, 1,558 companies had joined.

In 2019 16% of the global economy was covered by net-zero pledges; by 2021 net-zero-by-2050 pledges covered 70%. “The mobilisation of finance and business is very much driven by the 1.5-degree target,” says Stephanie Maier of Climate Action 100+, an investor-engagement group with 700 members holding nearly $70trn-worth of assets.

The urgency engendered by the 1.5°C target may be one of the reasons why, in the years since Paris, the peak temperatures seen on projections of what will happen if countries honour their pledges have steadily dropped. According to the un Environment Programme (unep) the range of temperatures by 2100 is around 2.8°C under current policies, and 2.4°C if countries live up to all the commitments about future policy made to the unfccc in Paris and since. That is real progress.

At the same time, seeing the target treated as attainable has led many to believe that added political will and increasingly fervent denunciations of fossil fuels can get the range of the possible all the way down to a warming of just 1.5°C. Thus, before the cop26 climate summit it hosted in Glasgow last year, the British government framed its goals for progress in terms of an aim to “keep 1.5 alive”. Two weeks later, it deemed its modest achievements to have provided the life support necessary.

That was, to put it mildly, misleading. This year, as the climate world meets in Sharm el-Sheikh on the Red Sea for cop27, hosted by Egypt, it would be far better to acknowledge that 1.5 is dead.

An emissions pathway with a 50/50 chance of meeting the 1.5°C goal was only just credible at the time of Paris. Seven intervening years of rising emissions mean such pathways are now firmly in the realm of the incredible. The collapse of civilisation might bring it about; so might a comet strike or some other highly unlikely and horrific natural perturbation. Emissions-reduction policies will not, however bravely intended.

Most in the field know this to be true; those who do not, should. Very few say it in public, or on the record. An activist movement based on galvanising enthusiasm is hard put to admit defeat on its chosen goal. Doing so can also feel, to those who care, like giving up on the poorest, who will suffer more than any others after the threshold is breached.

But the truth needs to be faced, and its implications explored. What does the certainty of a post-1.5°C world mean for the planet? Can a world which warms significantly more find its way back? And what will missing a totemic target mean for the credibility and sustainability of continued efforts to limit climate change?

Welcome to the machine

To see why 1.5°C is dead, and also to understand how it contrived to remain plausible for as long as it did, look at what is called the carbon budget: the amount of cumulative carbon-dioxide emissions associated with a specific amount of warming. Such budgets can be estimated pretty well from climate models; they are among their more robust products and among the most useful for policy.

With a sense of the budget in question, other modellers can try and produce emission pathways that deliver what the budget requires, using computer models which couple the climate to the economy which aim to be consistent with the science of both. These don’t allow emission cuts to increase arbitrarily, but only at rates consistent with possible investment and other constraints such as maintaining reasonable supplies of energy.

According to the ipcc the budget for a 50% chance of avoiding more than 1.5°C of warming is 2,890bn tonnes of carbon dioxide. Some 2,390bn of this had already been emitted by 2019. That left a pre-pandemic carbon budget of 500bn tonnes. Since then, a further 40bn tonnes has been emitted each year, roughly, leaving less than 400bn tonnes in the budget.

What sort of scenarios can be imagined for spending such a sum of smoke?

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