The world will soon shoot past 1.5°C. What does this mean?

Did you know that global heating will unavoidably soar past the 1.5°C temperature goal over the next three to four years? This is certain, despite our efforts to address the climate crisis.

In fact, a recent United Nations report found that with current climate and energy policies, the world is on track to heat 2.6°C above industrial levels by the end of this century. This is well beyond the Paris Agreement target of 1.5°C, and we know the dangerous consequences: more forest fires, extreme weather, loss of nature and rising seas.

Governments, scientists and communities affected by climate change are meeting this week in the Turkish city of Antalya for COP31, the annual UN climate conference. Australia is leading the negotiations as part of a compromise deal struck with Turkey at last year’s meeting.

At COP31, expect to see a strong push for action to keep 1.5°C “within reach”. This means that even if the world temporarily overshoots 1.5°C, emissions cuts and massive carbon removal could, theoretically at least, bring temperatures back down by the end of the century.

So, why is the 1.5°C target so significant? And how was this goal decided?

Where did 1.5°C come from?

In the 1990s and early 2000s, scientists and policymakers aspired to limit global warming to no more than 2°C above pre-industrial levels. But by the mid-2000s, there were concerns that limiting global warming to 2°C was going to be very challenging, if not unachievable.

Before 2015, the 1.5°C target received little attention in UN climate negotiations, with structured discussions only during 2013-15. In fact, its inclusion in the Paris Agreement – the international treaty to cut emissions — was pushed by an informal coalition of small island nations, supported most prominently by the European Union and the United States. Known as the High Ambition Coalition, this group said 1.5°C was the only target that could give citizens from their nations a future.

Following the Paris Agreement, the United Nations Framework Convention on Climate Change immediately requested a special report on the implications of the 1.5°C target. It found major differences in the risks to natural and human systems between 1.5°C and 2°C.

So this more ambitious 1.5°C target came largely as a condition of small-island states accepting the Paris Agreement. It was acclaimed by some as a target set by the people, which superseded the 2°C target that resulted from sustained scientific and policy discussions.

Overshooting 1.5°C

A recent UN report confirmed that global emissions reductions have not been enough to stop global warming passing 1.5°C in the next few years.

While calls for the 1.5°C target came from the coalition of small island states, UN assessment reports published after the Paris Agreement showed it would be largely impossible to prevent global warming passing 1.5°C. Instead, they predicted temporary overshoot scenarios, where 1.5°C was initially exceeded and large-scale carbon dioxide removal used to bring temperatures back down by the end of this century.

The fact we are soon to cross 1.5°C is consistent with science that has been developed over the past decade. But it remains devastating to small island nations around the world, which are feeling the impacts of climate change and sea-level rise.

Importantly, every additional degree brings us closer to potential “tipping points” – where the complex systems we rely on, such as climates and ecosystems, can abruptly shift once a critical threshold is crossed. These include changes in the ocean currents that bring warmth to northern Europe and increased emissions from thawing permafrost.

Is it realistic to remove that much carbon?

The only way to reverse temperature increases once we overshoot 1.5°C is through deep emissions cuts and large-scale carbon dioxide removal. If we overshoot beyond 1.8°C, the science suggests it will be very difficult, if not impossible, to engineer a temperature decline. This is because of the extraordinary quantities of carbon dioxide removal required.

There are clear limits to the amount of carbon that can be removed from the atmosphere. The UN’s Intergovernmental Panel on Climate Change estimated that for every 1,000 gigatonnes (billion metric tonnes) of carbon dioxide emitted, the global mean temperature increases by 0.45°C. This means, for example, we would need to remove 660 gigatonnes of carbon dioxide to correct an overshoot of 0.3°C. The more we go over our targets, the harder, longer and more costly it will be to return. At some point, damage becomes irreversible.

To put that in context, the global reforestation and the establishment of new forests captures and stores 2.2 gigatonnes of carbon dioxide each year, mainly in China, Europe and the US. This is equivalent to about a 5% carbon offset of current carbon dioxide emissions from fossil fuel.

It’s possible to increase forest area, but there are limits to how much land can be reforested without negative impacts on biodiversity, water availability and rural and Indigenous communities.

Meanwhile, technological solutions such as direct air capture provide only 0.002 billion tonnes of carbon removal annually. These technologies have the capacity to grow, but will need considerable development to reduce their cost and energy use.

The best chance we have

Over more than 30 years, the COP process has been central to making climate action a near-universal commitment. The Paris Agreement created a process for countries to continually strengthen their pledges to cut emissions, and improved transparency.

These annual summits have also created a crucial platform to pressure governments and foster cooperation, particularly between developed and developing nations. The exponential global growth in clean energy owes much of its success to government policies steered by UN summit negotiations.

While the UN’s climate agenda has not moved at the necessary speed, there is no alternative forum to these summits that offers a way to ratchet up global climate ambition.

This year, COP31 has the opportunity to turn the soon-to-be-crossed 1.5°C Paris Agreement target into more aggressive policies for faster emission cuts, and ensure the flow of finance to support sustainable development for all nations.