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Replanting trees is one of the better ways to remove carbon from the atmosphere. CIFOR/Flickr, CC BY-NC-ND

Keeping warming below 1.5°C is possible - but we can’t rely on removing carbon from the atmosphere

This week international leaders are meeting in Marrakech to thrash out how to achieve the Paris climate agreement, which came into force on Friday. The Marrakech meeting is the 22nd Congress of Parties (or COP22) to the United Nation’s climate convention. One of the key goals of the agreement is to limit global warming to well below 2°C, and aim to limit warming to 1.5°C.

With global greenhouse gas emissions still rising, this is a daunting task. Numerous models, including recent research, suggest we will not be able to achieve this without removing large amounts of greenhouse gases from the atmosphere later this century (known as “negative emissions”).

But scientists are becoming increasingly sceptical of the concept, as it may create more problems than it solves, or fail to deliver. Instead, we need to ramp up action before 2020, before even the earliest targets of the Paris Agreement.

Going negative

Some models suggest that up to 1 trillion tonnes of carbon dioxide needs to be removed from the atmosphere to meet the 1.5°C goal.

This idea is increasingly being called out as a risky and “highly speculative” strategy to limit warming to 1.5°C, as it puts food security and biodiversity at risk, and may not even be possible to deliver. The Convention on Biodiversity has also now weighed in on the issue, declaring that carbon removal techniques are highly uncertain.

A recent report from the Stockholm Environment Institute (SEI), summarised here, argues that the scale of negative emissions assumed by many climate models is improbably high.

The key components of negative emissions are reducing deforestation, planting trees, and an untested technology called “bioenergy with carbon capture and storage” or BECCS. The involves burning plant matter to produce energy, capturing the waste CO₂, and then storing it underground. The result is less CO₂ in the atmosphere.

But there are several problems with these strategies. For one, the scale of land required for the expected level of negative emissions suggests serious social and ecological risks, since land plays a crucial role in food security, livelihoods and biodiversity conversation.

Indeed, the scale of bioenergy supply in many cases is equivalent to the current global harvest of all biomass – for food, feed, and fibre - assuming a doubling of human harvest of biomass by 2050.

The SEI paper argues that the risks and uncertainties associated with negative emissions could lock us into much higher levels of warming than intended, substantially undermining society’s overall mitigation efforts.

Better ways to remove carbon

So does all of this mean the 1.5°C goal is out of reach? Some may think so.

However, the SEI analysis finds that if emissions were cut sufficiently quickly and ambitiously, we wouldn’t need to rely so much on negative emissions. We could also choose negative emissions methods with lower impacts on biodiversity, resource demands, and livelihoods.

The SEI analysis optimistically suggests that a maximum of 370 billion to 480 billion tonnes of CO₂ could be removed without exceeding biophysical, technological and social constraints. This would be done through protecting forests and allowing degraded forests to regenerate, along with some reforestation.

Even that would be extremely challenging to achieve, but done right, for example through community forestry and agro-ecological farming,, climate mitigation and sustainable development could go together.

In fact, securing land rights of indigenous peoples and local communities who protect and preserve the carbon stocks in forests is one of the most cost-effective forms of climate mitigation we have, with obvious social co-benefits.

Scaling up

The real threat of negative emissions is the potential to delay emissions reduction into the future. Many modelled pathways for 1.5°C that include substantial negative emissions suggest that emissions do not begin to decline until the late 2020s.

But limiting negative emissions to lower levels would require immediate global mitigation on a scale greatly exceeding that which has so far been pledged by nations under the Paris Agreement.

We cannot wait until 2020 to speed up global action on climate change - less action now will mean more work later.

Key for strengthening pre-2020 action in Marrakech will be a facilitative dialogue on enhancing ambition and support and a high level ministerial meeting on increased ambition of 2020 commitments under the Kyoto Protocol.

Many countries, including Australia, still have completely inadequate targets for 2020, making arguments about whether they are on track to meet them or not moot.

The Moroccan government has dubbed Marrakech the “action COP”. Action here must focus on the urgent need for global emissions to begin declining before 2020, and on the finance needed to deliver it. This includes scaling up the rollout of renewable energy, halting and reversing the loss of the world’s forests, and tackling rich world consumption patterns to ensure equitable mitigation pathways.

Limiting global warming to 1.5°C is not only possible, it is the only chance of survival for the most vulnerable communities around the world, who are increasingly exposed to rising sea levels, drought and food shortages.

As Erik Solheim, head of the UN Environment Program (UNEP), and Jacqueline McGlade, UNEP’s chief scientist, wrote in a recent report, those most vulnerable “take little comfort from agreements to adopt mitigation measures and finance adaptation in the future. They need action today”.

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