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11 takeaways from the draft UN report on a 1.5C global warming limit

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Climate Home News

Under the Paris Agreement, governments worldwide agreed to hold global warming “well below 2°C” and to aim for 1.5°C.

The inclusion of that second, tougher, goal was a victory for small island states and other countries on the front line of climate change. It was an acknowledgement of fears that higher temperature rise posed an unacceptable threat to their futures.

But the vast bulk of research and analysis prior to 2015 centred on the 2°C threshold, a more established international target. What would it take to bend the curve to 1.5°C?

Enter the Intergovernmental Panel on Climate Change (IPCC). The climate science body agreed to produce a special report on 1.5C, summarising all the available evidence.

Climate Home News has obtained an early version of the five-chapter report, which is due to be finalised in September.

The IPCC stressed it was a work in progress and may change substantially. It is open for review by experts and governments, and may incorporate further studies published by 15 May. Read the draft summary for policymakers in full here.

What is clear from the content so far, though, is there is not much time left. Here are the main takeaways.

1. We’re close to the line

The world has already warmed 1C since pre-industrial times. At the current rate, we will pass 1.5C in the 2040s.

Definitions are important here. This is based on a 30-year average global temperature, centred on the year in question, compared to 1850-1900.

Parts of the world, for shorter periods of time, are almost certain to exceed 1.5C warming sooner than that. The UK Met Office sees a one in 10 chance the global average will flicker over 1.5C within five years.

2. 1.5C is risky

The fingerprints of climate change are already visible on extreme weather events, sea level rise and related impacts on ecosystems and human society. Each notch of warming brings more disruption.

At 1.5C, tropical reefs are at “high risk” of no longer being dominated by corals. The Arctic could become nearly ice-free in September. There will be “fundamental changes in ocean chemistry” that could take millennia to reverse.

3. 2C is riskier

The next half-degree ramps up the risk of flood, drought, water scarcity and intense tropical storms. There are knock-on effects: reduced crop yields, species extinction and transmission of infectious diseases like malaria. And these pressures multiply the threat of hunger, migration and conflict.

An extra 10cm of sea level rise is predicted this century with 2C compared to 1.5C. It also raises the risk of Greenland and West Antarctic ice sheets collapsing over the long term, dooming future generations to multi-metre sea level rise.

4. Poor and coastal communities will be hit hardest

Vulnerable communities are already experiencing threats from climate change. At both 1.5C and 2C these effects scale up. When crops fail, smallhold farmers may lose their livelihoods and be compelled to leave their homes, while the urban poor suffer from food price spikes.

Fishing communities may see their catches dwindle. Coastal settlements are particularly exposed to storm surges and flooding.

5. “Rapid and deep” emissions cuts are needed…

Meeting the 1.5C goal is a huge ask. It implies cutting greenhouse gases faster than ever before across all sectors of the economy.

With the exception of recent upheaval in electricity supplies, the rate of change required “has no documented historic precedents”.

These shifts “require more planning, coordination and disruptive innovation across actors and scales of governance than the spontaneous or coincidental changes observed in the past”. They won’t happen by chance.

6. …and negative emissions…

At the same time, carbon dioxide needs to be sucked out of the atmosphere. It gets little attention from politicians or policymakers, yet every single pathway to 1.5C relies on this to some extent.

Depending on the scenario, 380-1130 gigatonnes of CO2 should be removed. Firstly, this is to cancel out the leftover emissions after everything that can be cut has been cut. Secondly, it makes up for overshooting the emissions limits that would keep temperatures below 1.5C.

The more emissions cuts are delayed, the more rests on negative emissions technology, which could be problematic.

7. …and luck

All of these models are probabilistic: assumptions about population, the economy, climate dynamics, policies and technologies go in and the likely impact on temperatures comes out. Some uncertainties are beyond human control.

Scenarios that give a 66% chance of holding temperature rise below 1.5C throughout this century are “already out of reach”, according to the draft summary.

That leaves a narrow path to walk to stay within the 1.5C threshold, or the prospect of overshooting and using negative emissions to restore the balance by 2100.

8. It’s all about the overshoot

As global warming outpaces efforts to curb it, models increasingly rely on “overshoot” to keep international targets within reach. That goes for 2C as well as 1.5C.

The bigger the overshoot – and scenarios in this report reach up to 1.9C before returning to 1.5C by 2100 – the more drastic action is needed to correct it.

And while temperature rise may be reversible, some impacts are not. An ice sheet cannot un-collapse or an extinct species be brought back to life.

9. Radical action has trade-offs

Scaling up negative emissions in line with the 1.5C goal may clash with efforts to end hunger.

The main two measures relied on to remove CO2 from the air are increasing forest cover and bioenergy with carbon capture and storage (Beccs).

The latter, which involves burning wood or other plant matter to generate electricity and pumping the emissions underground, is particularly controversial. Both require large amounts of land, potentially conflicting with food production.

“There is a high chance that the levels of CO2 removal implied in the scenarios might not be feasible due the required scale and speed of deployment required and trade-offs with sustainable development objectives,” the draft states.

The report does not make a judgement on which poses a greater threat to global food supply: bioenergy demand or 2C warming.

10. Beware techno-fixes

The draft takes a sceptical line on solar geoengineering, a prospective technology to cool the planet by reflecting heat into space.

Ethical implications, governance issues and public resistance could make it “economically, socially and institutionally infeasible”.

11. Prepare for social change

As much as any technology, 1.5C depends on people changing their behaviour.

That means the rich eating less meat, using energy sparingly and forgoing private cars. And it means tackling institutional barriers to action like public attitudes, lack of resources or special interests.

Source: Climate Home NewsReproduced with permission.  

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  • Joe

    I love that mention in point 11. “…people changing their behaviour.” I like to think I am a bit of an optimist but I just can’t see the masses in Australia changing their behaviour anytime soon, not at least voluntarily. We already have a ‘climate emergency’ but people seem to rather oblivious to it all…the future can take care of itself sort of attitude. The meaningful change in people’s daily lives will only come when the crisis is on the doorstep and that my friends will be far too late in climate change affairs. I’m 60 years young and won’t be around too much longer but my nephews and nieces have no such luxury…..good luck to them with the future.

    • Elizabeth Stewart

      What we need is governments which provide incentives to change behaviour. In Australia, our problem is 2 entrenched major political parties which have vested interests in stalling – one acting on behalf of the owners of fossil fuel enterprises; the other acting on behalf of their workers. Unless this changes, nothing else will.

      • Joe

        I think the term commonly used to describe ‘stalling’ is…kicking the can down the road. In relation to climate change it will be the generation that follows that has no choice but to adapt as best they can to what the current generation has bequeathed them. We have a climate emergency, the scientists have warned us for over 20 years and yet we still have resistance to change and where change is happening it is not nearly enough or quick enough. The COALition are climate criminals in my opinion and should be prosecuted.

  • john

    The problem is this NO one cares.
    No honestly no person cares because the majority of people living on earth at this moment cares.
    DO you honestly think anyone is going to do anything ?
    NO
    Yes it depresses me too.
    But that is the situation we are faced with.

  • Julia Mercado

    Read this in light of the water issues in S. Africa – where straight in your face crises loomed, and the populace was still skeptical/unbelieving that THEY needed to change their behavior. Not very encouraging. Better messaging will only be met with the same skepticism.

    • Joe

      South Africa has had a long drought and Cape Town is the so called ground zero. And yesterday I saw an update on affairs in Cape Town. Only weeks ago ‘Zero Day’, where the private taps would be turned off, was to be in April. But because of the last minute emergency water saving measures that have been brought in this year the authorities ‘moved’ Zero Day to…June and hailed this as some sort of triumph. I love the thinking, NOT. Climate change has affected the rainfall across South Africa but “…people changing their behaviour” did not mirror the change in water circumstances until it has been forced upon them as we now see in Cape Town.

      • itdoesntaddup

        Fake news. The reality is that the relative drought in Cape Town is nothing unusual – there have been several similar periods over the past 100 years with low rainfall over several consecutive years. The problem has been caused by

        a) rapidly rising population;
        b) failure to expand reservoir resources;
        c) failure to maintain the system, leading to extensive leakage losses.

        This has not been helped by extensive corruption and embezzlement of public money, or at the least, diversion of public money to other causes. It is a matter of great convenience to be able to blame these political failings on “climate change”, so as to deflect attention away from the combination of incompetence, corruption and theft.

  • Fake Prosecutor

    Human overpopulation is the primary cause of the problem. Until we address population we have little chance of avoiding disaster.

  • George Darroch

    Can we stop pretending? Please.

    Enough of the denialism from the climate community. We are on emissions trajectory for 3-7C above our 1950-1980 climate, and no country on earth has made emissions reductions consistent with 1.5C.

    All that the low targets do is give comfort to do-nothing politicians who think that they can do it easily, without upsetting or offending any industries or groups of voters. It’s not correct, and it’s not helpful.

    • Joe

      There has to be some hope. The alternative is to just give up which really is not an option. The 1.5 degree aim is unachievable and with the world’s emissions still increasing you would have to say that the 2 degree limit is a rather optimistic target. Talking the talk is one thing but perhaps when the environmental changes really start to impact walking the walk will finally happen….nothing like an immediate crisis to focus the mind and spirit into action.