Professor Hans-Otto Pörtner is a climatologist, an oceans’ expert and co-chair on the International Panel on Climate Change (IPCC) Sixth Assessment Report, in particular the volume on impacts, adaption and vulnerability. In an exclusive interview with Horizon Magazine ahead of COP27 in Sharm-El-Sheik in Egypt, Prof Pörtner discusses climate change evidence from IPCC reports and his own view that not enough is being done.
How has the evidence for climate change shifted in recent years?
Until a few years ago, people would say that there may be a natural component to climate change. But the evidence is unequivocal now that the climate change we’re seeing now and have seen since pre-industrial times is entirely human-made. We are very confident of that.
How are the oceans impacted by climate change?
At one time, people thought that we could dispose of excess carbon dioxide in the ocean to get rid of it. This was not a good idea, because there are direct impacts on ocean ecosystems. The three climate change impact drivers in the ocean are temperature extremes, low oxygen levels and high CO2 levels – we call these the deadly trio.
This combination has been seen in mass extinction events in Earth’s history, where climate extremes have been a major driver of species extinctions, observed in the marine fossil record.
Has the influence of climate change on the oceans been overlooked?
It has been reported on by the IPCC, but not gained as much attention as what is happening on land, such as say, crop production or extreme weather events. During the last few COPs, there’s been an effort to bring the oceans more into the climate discussion. Sea and ice cover almost 80% of the planet, and the ocean is very relevant for the human population in terms of extreme weather events, floods and fisheries.
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The evidence is unequivocal now that the climate change we’re seeing now and have seen since pre-industrial times is entirely human-made.
What has climate change meant for animal species?
Observations are telling us that species are on the move, further north or further south to higher latitudes. We are starting to see processes similar to previous evolutionary crises, when species moved out of the tropics, and the tropics became devoid of higher life during the Permian-Triassic mass extinction event. We have started that process, with climate change just adding to the destructive influence humankind is having on nature.
We also see reductions in fish stocks in the ocean, which will continue, depending on the degree of climate change. We can’t project fully yet what ecosystems will look like in several decades, but certainly this turnover in the system is not good for productivity and not good for fisheries.
Do you think public opinion has shifted?
The mobilisation of the younger generation, which was a consequence of ‘the 1.5°C report’ (follow the link to find the IPCC special report entitled Global Warming of 1.5°C) has helped to move the agenda forward. Unfortunately, as soon as people’s economic interests are tied to old models, it becomes more challenging.
Hans-Otto Pörtner © Kerstin Rolfes/Alfred-Wegener-Institut
What insights did the latest reports from the International Panel on Climate Change (IPCC) offer?
The risk estimates in previous IPCC reports were a little too conservative, we know now that risk develops more strongly with warming. Also, there is a clear differentiation now to be made between 1.5°C of warming and 2°C, as this relatively small temperature change means a lot in terms of impact.
Just consider this last summer how much damage climate change has done in the Northern Hemisphere. And the Southern Hemisphere too – I just saw today that another huge weather system is over the east coast of Australia, which is expecting heavy precipitation and flooding.
The most recent assessment says the likelihood of extreme weather events is several-fold higher with climate change. Our ambitions to restrict warming to 1.5°C should be strengthened.
Have the IPCC and scientists been too cautious in the past in their reports?
There has been a certain hesitation to get into stronger statements and we are not supposed to be prescriptive about policy, which may make us appear to be too conservative. Also, it has been about developing a consensus across a large group of people. From report to report, we may have lagged somewhat behind in terms of making fully realistic projections and the climate impacts have come faster than we thought and have been more hefty than we had thought.
What positive effects have the IPCC reports had?
The answer must be that the effect on policy and society has not been strong enough. The setting of international goals has been okay, but the implementation has always been too slow.
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Subsidies for fossil fuels need to be shifted away from fossil fuels to renewables. Putting solar panels on half of the world’s roofs would satisfy energy demands.
How should we understand adaptation to climate change?
We know that we already have about 1.2 °C of global warming, and clearly the natural world and human society is going to have to adapt to this change. Not doing anything about climate change is not an option. We might adapt by installing better insulation in our house or highly efficient air conditioning. Adaptation, though, can also include mitigation measures such as reducing activities that cause more emissions.
Sometimes adaptive measures work against us – such as if you build a hard wall on the seashore to protect yourself from sea level rises, when this is clearly bad for the ecosystem outside that wall, because space is shrinking and species cannot move inland with the rising water level. Also, such hard protection measures can cause surprises when the water goes over the wall. Better to use natural systems for coastal adaptation.
Has there been enough urgency and progress made at previous COPs?
Too little has happened. There has been a tendency to solve short-term issues without considering the long-term implications, for example by compromising with lobbyists and thereby watering down climate and biodiversity targets. Subsidies for fossil fuels need to be shifted away from fossil fuels to renewables, and bureaucratic hurdles removed for building wind farms and solar panel installations. Putting solar panels on half of the world’s roofs would satisfy energy demands.
What is the best outcome you can hope for from COP27 in Egypt this year?
That we move away from a north-south divide when discussing losses and damages and towards a position of shared responsibility with respect to how we are going to secure a liveable future for the planet concerning its ecosystems and human societies.
In principle, everybody should be making contributions to a pot of money where countries can get support for transitioning into a society built on renewables, not fossil fuels. International solidarity and justice as well as making contributions according to past and current emissions should be guiding principles when setting up a system where no country gets left behind.
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