How to reach „Climate Resilient Development”? Professor Hans-Otto Pörtner on consequences of global warming

How to reach „Climate Resilient Development”? Professor Hans-Otto Pörtner on consequences of global warming

Professor Pörtner, first of all, we would like to thank you for accepting our invitation to the Sustainable Economy Summit and agreeing to this interview. Could you briefly describe what is your field of expertise as a scientist?

I’m a trained physiologist and ecologist and have been researching the impacts of climate change on ocean life for more than 25 years at the Alfred Wegener Institute for Polar and Marine Research in Bremerhaven, Germany. My work focuses on how ocean warming, ocean acidification, and the increasing lack of oxygen are affecting vital biochemical processes in marine life. Therefore, we analyse the changes in the genome, at the cellular and whole organism level as well as shifts at the species and population level and within entire ecosystems. Our findings are crucial if we want to understand how marine life is changing due to climate change.

As an expert on the matter of climate change and its impact on marine ecosystems, what do you consider to be a crucial factor influencing the biodiversity of seas and oceans?

Climate change is one of many interacting drivers of change in our ocean. It combines with other stressors such as overfishing, habitat destruction, and pollution, amplifying the overall risks to ecosystems and people. Together, they cause even more damage than each one of those stressors alone. Five years ago, when the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES) published its “Global Assessment Report on Biodiversity and Ecosystem Services”, experts concluded that climate change was responsible for about 20 percent of biodiversity decline in our ocean. This share has increased dramatically since then I think, especially due to increased ocean warming. Our world has just experienced record sea surface temperatures for more than 365 days in a row. For many warm-water corals and other immobile organisms, this heat has already been deadly. Others are losing habitat and migrating poleward in order to stay in their preferred temperature ranges. Temperature is currently the key driver of change in the ocean, increasing acidification and oxygen loss are exacerbating the impact of warming.

Do the environmental changes affect wildlife from different climate zones in the same way?

Each species lives in a specific temperature range that it has adapted to – meaning that individuals grow and reproduce best if the surrounding temperature stays within this thermal window. Increasing temperatures and extreme events such as droughts, floods, and heatwaves are exposing plants and animals to life-threatening conditions everywhere, including in the ocean. These include climatic conditions not experienced for at least tens of thousands of years. Observed increases in their frequency and intensity of climate extremes are starting to exceed the ability of many species to adapt. Based on increased observations and a better understanding of processes, we know now that the extent and magnitude of climate change impacts on nature are greater than previously assessed. The impacts we see today develop much faster, they are more disruptive and more widespread than we expected 20 years ago. For numerous ecosystems, climate change impacts are an additional stress and even a deadly burden, depending on the degree of global warming.

In your opinion, what are the most pressing challenges induced by climate change?

Climate change is a threat to human well-being and the health of the planet. Global warming of 1.15°C has already caused dangerous and widespread disruption in nature and affected the lives of billions of people, despite efforts to adapt. About half of the plants, animals, and marine species studied globally are moving poleward or, on land, to higher altitudes to find conditions they can survive in. Increasing extremes have exposed millions of people to acute food and water shortages, particularly in Africa, Asia, Central and South America, on small islands, and in the Arctic. And the number of days, when people cannot work outside due to deadly heat and humidity is rising, especially in the Tropics. These three examples show that climate change has become an existential threat. To avoid mounting losses, urgent action is required to adapt to climate change, at the same time as making rapid, deep cuts in greenhouse gas emissions. Securing a liveable future for all is already challenging at current global warming levels. The prospects of what we call “Climate Resilient Development” will be further limited if global warming exceeds 1.5°C. And it will not be possible in some regions if warming exceeds 2°C. 

In one of your interviews, you mention that the climate, biodiversity, and human society are intertwined. Could you elaborate on this connection?

Climate, nature, and human society are closely interlinked and affect and support each other in various ways. For example, human actions result in emissions of greenhouse gases which cause global warming and climate change. At the same time, we are polluting, overexploiting, and destroying vast areas of land, freshwater, and ocean ecosystems. This weakens the ability of these ecosystems to regulate climate and provide food, clean water, cooling, and other services that human life depends upon.

Without healthy and functioning ecosystems, human societies have fewer options to adapt to a changing climate. In addition, nature is under pressure and therefore has a decreased capacity to withstand weather and climate extremes such as heat, storms, sea level rise, or acidification and oxygen loss in the ocean. The degradation of ecosystems, including from further warming, can release carbon dioxide and other greenhouse gases, and thus further escalate climate change and its impacts. This gives rise to a vicious cycle that increases current and future risks for people and nature and prevents us from reaching Sustainable Development Goals such as “zero hunger”, “no poverty” or “sustainable cities and communities”.

But there is also good news: Understanding these interdependencies between climate, nature, and people, enables us to break the vicious cycle that escalates climate change and its impacts and to re-balance the system(s). When we stop looking at the individual parts in isolation and start thinking of the whole picture – treating climate, people, and nature as interdependent building blocks of life on Earth – we will be better able to reduce global warming and climate risks, and improve the resilience of human societies and nature.

In what way did your work on the Intergovernmental Panel on Climate Change (IPCC) influence your understanding of the urgency and importance of addressing climate change?

I have been involved in IPCC Assessments since 2003 – first as a Lead Author for the Special Report on Carbon Dioxide Capture and Storage in the 4th Assessment Cycle, then in the 5th Assessment Cycle as a Coordinating Lead Author of the Ocean chapter in the Working Group II report. In the 6th Assessment Cycle, I was elected as Co-Chair of Working Group II which focuses on climate change impacts, adaptation, and vulnerability. With each role and task, my knowledge and understanding of the Earth system and its changing climate grew. The science is clear: Climate change risks and impacts will grow exponentially with each additional fraction of warming. We are running out of time to prevent drastic changes and to secure a liveable future for all. Climate change and the loss of biodiversity are the two most pressing issues of our time and we should invest whatever it takes to stop and reverse them. 

What are the key findings of the IPCC Sixth Assessment Report that you have largely contributed to?

An IPCC Assessment is done by three Working Groups and each of them has hundreds of authors who work voluntarily. In the Sixth Assessment Cycle, our team of Working Group II made a huge effort to highlight the interlinkages between nature, climate, and people in each of our report’s chapters. In addition, we showed which adaptation options are feasible and would create co-benefits for climate, people, and nature. And we describe what it takes to get on the path toward climate-resilient development – a task identified by close cooperation across various scientific disciplines.

What role does education have in addressing climate change? Do you think that the level of awareness of the ongoing environmental shift is sufficient?

Knowing the causes and impacts of climate change is crucial if we want to limit global warming successfully. In a world of multiple crises, every action, every choice, and every decision matters because each of them can take us away from, or towards, a climate-resilient sustainable world. However, effective climate action ranks low on the priority list of many decision-makers, possibly due to the lack of understanding of the challenges involved. The existential topics of climate change, biodiversity loss and pollution should be cross-cutting in all education systems, so people understand better which priorities need to be met. Mostly due to economic reasons, policymakers agree on compromises that cost us precious time, as we have seen during COP28 in Dubai, where governments could not agree on the urgently needed phase-out of fossil fuels. The inconvenient truth is that we are not on track to achieve a climate-resilient, sustainable world that would secure a liveable future for us, our children, and future generations.

You have recently been awarded the Planetary Health Award in recognition of your achievements. Do you feel that your field of study earns enough credit?

I was very honoured to receive this award. But I think that I speak for many researchers when I say that effective science-based action against climate change, biodiversity loss, pollution and poverty would be the best recognition a climate scientist could ask for.

Looking ahead, what are your hopes with regard to nullifying the negative impact of climate change?

Climate change is happening much faster than we previously thought. Considering the current long-lasting ocean record temperatures, it even seems like the Earth system is already moving into uncharted territory. Any further delay in concerted global action will miss a brief and rapidly closing window. We need to limit global warming as close as possible to 1.5 degrees Celsius because we do not have any other option to keep planet Earth a liveable space for all of us.

Prof. Dr. Hans-Otto Pörtner, marine biologist and Co-Chair of IPCC Working Group II in the Sixth Assessment Cycle (2015-2023)

Hans-Otto Pörtner is a physiologist and marine biologist. He conducted research for more than 25 years at the Alfred Wegener Institute in Bremerhaven and is one of the world’s best-known experts on the effects of climate change on marine life and beyond.

His career began in Münster and Düsseldorf, where he studied biology and obtained his doctorate in 1983. After research stays in Göttingen and Canada, he habilitated in Düsseldorf in 1990. From 1995 to 2023, he headed the research group for Integrative Ecophysiology at the Alfred Wegener Institute.

During his career, he has investigated how ocean warming, ocean acidification and oxygen depletion affect the biochemical processes of marine life. His pioneering findings on climate change impacts on marine organisms have earned him worldwide recognition. As Co-chair of IPCC Working Group II, he made a significant contribution to the 6th IPCC Assessment Report. Hans-Otto Pörtner is an elected member of the European Academy of Sciences and was appointed by the German government to its Advisory Council on Global Change (WBGU) in 2020.

Last Updated on April 22, 2024 by Anastazja Lach