COP28 gave us something we can work with, but it is not enough

A marine scientist from Kasetsart University takes photos of green sea water caused by plankton bloom known to kill marine life, at Chonburi's coastline, Thailand, September 14, 2023

A marine scientist from Kasetsart University takes photos of green sea water caused by plankton bloom known to kill marine life, at Chonburi's coastline, Thailand, September 14, 2023. REUTERS/Athit Perawongmetha

Keeping the planet within ‘safe’ warming limits will require dealing with other planetary boundaries being crossed

Johan Rockström is director of the Potsdam Institute for Climate Impact Research (PIK).

As the dust settles on the COP28 climate talks, with a welcome but heavily overdue agreement to shift away from fossil fuels, it’s time to take stock of where we stand on the state of a planet in peril.

The focus in Dubai was to hold alive the limit of 1.5 degrees Celsius of global warming, as breaching this climate boundary is likely to trigger multiple tipping points.

Currently we are following a path to disaster, which would take us to around 2.7C of global warming above pre-industrial levels by the end of this century.

This would not only exacerbate the already-palpable increase in devastating extreme weather events, but it would also represent a perturbation of the climate so extreme that one third of the global population – more than 2 billion people – would be living in regions where average temperatures lie outside the human climate niche.

On current projections, we are likely to breach the ‘safe’ 1.5C limit of warming in the next 10-15 years which will be an unparalleled stress test for our planet.

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Earth’s natural defences, spearheaded by the buffering capacity of the biosphere, the part of the earth where living things exist, will be essential to fend off systemic change that could compromise the conditions that have allowed humans to thrive.

The most recent assessment of the health of our planet shows that decarbonising the global energy system alone will not be enough. In September of this year, we published the third scientific assessment of the state of the planet, concluding that six of nine planetary boundaries have been breached.

The planetary boundaries are the environmental processes and systems underpinning the stability, functioning and life-support capacity of the Earth system, of which climate change is one. Others include biosphere integrity, land system change, ocean acidification and ‘biogeochemical flows,’ or how water and key elements like phosphorous flow between living organisms and the environment.

That six of nine planetary boundaries are breached is a dire warning signal to the world.

In its most narrow climate terms, this tells us that we are deep into the climate crisis, experiencing climate extremes as we reach the warmest temperatures on Earth over the past 110,000 years. At the same time, Earth is losing its stability and buffering capacity – the ability to dampen the stress caused by global warming. This is extremely worrying.

We know that it is only healthy oceans and natural systems that can buffer over 50% of CO2 emissions from fossil-fuel burning and over 90% of heat. Breaching biosphere boundaries weakens Earth's capacity to buffer stress and threatens stability.

Understanding the interplay of these boundaries, especially climate change and loss of biodiversity, is key. Pushing too far on the boundaries relating to land, biodiversity, nutrients, water, and pollutants, can, on its own, push Earth through the 1.5C limit.

Although our knowledge of how this will play out is evolving constantly, we know that the risk of destabilising our planet as a whole is now rising sharply.

The latest science foresees a likely risk of crossing certain tipping points if we pass 1.5C, including the irreversible melting of the Greenland and West Antarctic ice sheets, committing Earth's oceans to a 10-metre (33-foot) sea level rise, as well as the loss of livelihoods for hundreds of millions of people who depend on coastal tropical reef ecosystems, and feedbacks being triggered that would accelerate warming further.   

With the breaching of planetary boundaries, the ability of Earth to adapt to and buffer the pressure of unrelenting human activity, while still maintaining the conditions under which humans have developed and flourished, is waning.

Our planetary systems do not operate in isolation – crossing one can put others at risk. As a global community, the way we manage these risks needs to be much more integrated to reflect this interconnectedness.

On a more hopeful note, we have evidence that despite the pressures we have placed on the planet, Earth still holds a significant degree of resilience, continuing to buffer the climate and ecological abuse posed by unsustainable human enterprise.

Proof of this is presented in the 2023 global carbon budget which shows that the Earth system, despite indications of weakened carbon uptake capacity, particularly on land (due to droughts, fires, disease, and unsustainable exploitation), continues to be ‘our best friend’ by absorbing approximately 50% of the CO2 emitted from human sources.

Becoming stewards of all the planetary boundaries, and thereby restoring Earth’s resilience, is our window of opportunity for a safe landing for humanity on a manageable planet. In fact, the emerging best possible future for humanity is to cope with a period of (very likely) inevitable overshoot before returning to a world within a safe 1.5°C by 2100.

What is it that will bring us back from overshoot? Well, it is quite straightforward.

We need to decarbonise the world economy by 2050, cutting emissions by half each decade starting with 2030. We need to return to a safe operating space on terrestrial and ocean planetary boundaries, while hoping that no tipping points are permanently crossed. And we need to start scaling carbon dioxide removal technologies, as nature cannot restore energy balance on Earth alone.

Ultimately, it is very likely that the ocean will determine whether or not we can cool the planet after overshoot. That in turn hinges on the biological, physical and chemical health of our marine systems on Earth.

We have a window of opportunity for a safe landing, but it is closing quickly.

Any views expressed in this opinion piece are those of the author and not of Context or the Thomson Reuters Foundation.


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