September 25, 2019

expert reaction to the Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC)

The Intergovernmental Panel on Climate Change (IPCC) has published a report on the Ocean and Cryosphere in a Changing Climate (SROCC).

Prof Andrew Shepherd, Director of the Centre for Polar Observation and Modelling, University of Leeds, said:

“2019 has been a bad year for Earth’s ice; we’ve seen sharp reductions in the extent of sea ice in Antarctica for the first time, record summer melting in Greenland, and the complete loss of mountain glaciers in Iceland. 

“And yet these changes are not unexpected; we have had satellite measurements and climate models for nearly three decades – a generation – and we are still reporting the changes as if they are news.

“The real concern is for Antarctica and Greenland, because it has become increasingly clear that their ice losses are tracking towards the upper range of the IPCC’s predictions.

“So we need to start planning for 20 to 30 cm more sea level rise than is currently expected, and we also need to fix those models to make sure they don’t underestimate the impacts of global warming in future.”

Dr Arnaud Czaja, Reader in Physical Oceanography at Imperial College London, said:

“The report highlights how all people on Earth depend directly or indirectly on the ocean and the cryosphere: just think of the impact of Arctic sea ice reduction (about 50% of Summer sea ice loss over the last decades!) on the lives of the indigenous people of the Arctic, or how all of us are benefiting from the buffering role that the ocean is playing in storing heat and carbon globally.

“But this buffering role also comes with a cost for us: directly in terms of thermal expansion and as a result rising sea levels (the report illustrates how coastal cities will see a “once in a hundred year event” occur once a year in the next few decades); and also indirectly by affecting dramatically marine ecosystems (estimates shown indicate a decline of more than 30% in total animal biomass over the 21^st century over most ocean basins) and, ultimately, fisheries and the food source of millions of people.”

Prof Peter Wadhams, Professor of Ocean Physics at the University of Cambridge, said:

“There is no mention anywhere in this report of a very serious threat facing mankind, the release of methane from the seabed of the Arctic continental shelf seas. As the Arctic sea ice retreats the newly ice-free coastal seas are warmed to several degrees C, and the seabed layer of protective permafrost thaws. This is a serious omission.

“The underlying methane, in the form of methane hydrates, is released and forms rising plumes which vent to the atmosphere. It has been projected that if 50 GT of methane were released (a mere 8% of the content in the sediment) the result would be a global temperature rise of 0.6 C (Hope et al., Nature, 2013).

“There are many reliable field observations of increasing fluxes of methane (Shakhova, Semiletov, Nature, Science) so this has to be classed as (a) a current phenomenon which must be mentioned, (b) an existential threat to the planet originating in the cryosphere. Why then is it completely neglected in the summary for policymakers?”

Professor Grant Bigg, Professor of Earth System Science at the University of Sheffield, said: 

“What is very striking about this report is the degree to which change in so many environmental characteristics will occur despite even the best efforts to control emissions. Melt of the Earth’s glaciers and sea-ice will continue over the next few decades, leading to flooding hazards and ecosystem changes, sea level will continue to rise, ocean corals will continue to be stressed through increasing temperatures – these are just a selection of changes that will occur by 2050 even if the Earth’s warming is restricted to 1.5C. Environmental change will increasingly challenge governmental efforts to cut emissions and produce adaptation strategies.”

Prof David Vaughan, Director of Science at the British Antarctic Survey, said:

“The IPCC SROCC team highlighted a tripling of ice loss from Antarctica over the period 2007-2016, relative to 1997-2006 and similar from Greenland.  This is an extraordinary response in ice sheets that not so long ago we imagined too huge, too old and too slow to respond so quickly to climate change.  

“The report emphasises the urgent requirement for new science in the polar regions, and today in UK, US, Germany, Sweden and Korea, scientists are preparing the most ambitious joint field campaign in the history of Antarctic research (see www.thwaitesglacier.org). In just a few weeks, these researchers will be deployed to West Antarctica to begin their work to understand the changes in the oceans that have contributed to this accelerating ice-loss in this region and to help reduce uncertainty in Antarctica’s future contribution to global sea-level change.   

“And on Thursday, in Liverpool, the UK’s new Polar Research vessel the RRS Sir David Attenborough will be named by Duchess of Cambridge. This ship will deliver research on ocean change, sea-level rise and polar ecosystems and in coming decades and it will be witness to the dramatic changes IPCC has forecast.”

Dr Ali Mashayek, Lecturer & NERC Research Fellow at Imperial College London, said:

“This report highlights three fundamental issues that characterise most of the ongoing analyses and discussions on climate change. First, climate change impacts are wide ranging and highly non-local, affecting terrestrial and marine life from polar regions to equatorial oceans, from coastal regions to abyssal oceans. They do not recognise political borders and are often non-discriminatory with respect to human, animal and plant populations. Second, the impacts of climate change are long lasting and will extend well beyond 2100 even in the best-case scenario in which we reach net zero emissions by 2050. The slower we react, the more severe and long lasting the consequences will be. And third, the nature, spatiotemporal patterns and severity of climate change impacts are inherently difficult to predict due to the complexity of the tightly coupled physical, biological and biochemical components of the climate system.  All three of these issues highlight the urgent need for collective effort on global scale in which research, industry, policy making, and public education and engagement all act in a coordinated fashion towards a common goal. 

“One of the key messages of this report is that the adverse impacts of climate change are complex and, at time, coupled. As an example, consider the acceleration of sea level rise due to ice loss in Greenland and Antarctica. The global patterns of sea level rise are complex and some of the most significantly impacted regions are densely populated countries which have been exposed to increased flooding and threats to their food security and availability and quality of water resources. The severity of such impacts is expected to increase even if we achieve net zero emissions by 2050. Non-climate human activities, such as population growth, only complicates the problem as it demands more resources in already over-stressed regions. For example, in coastal tropical regions, population growth has led to significant areal decreases in coastal ecosystems such as seagrass meadows and mangrove forests. Such ecosystems, under attack by both climate change and population growth, are key to protecting the coastal regions against impacts of sea level rise, such as flooding, and play a key role in sustaining the food chain that facilitate sustainable fishing practices. The complexity of these problems provides a great opportunity for creativity and innovative solutions that can mitigate climate change while allowing for sustainable growth in local populations and economies.

“The report highlights the fact that while the oceans play a key role in climate change mitigation by absorbing a significant fraction of the anthropogenic carbon and heat, they also allow for rapid propagation of adverse impacts of climate change across the globe. Ice loss in polar regions impacts the tropics by exacerbating sea level rise and changes to tropical dynamics due to climate change can alter the ocean meridional circulation, which transports heat from the equator to the poles, thereby impacting the polar climates. Global ocean basins, through occupying 71% of the Earth’s surface and their coupling to the atmosphere, cryosphere and land, make sure that the impacts of climate change will be felt around the globe from the poles to the equator and from the coastal regions to the abyssal ocean. Climate change impacts will be realised on time scales ranging from few decades to several millennia, implying that the impacts are forthcoming, if not already here, and will last deep into the future.”

Dr Yves Plancherel, Lecturer at the Grantham Institute for Climate Change & the Environment, Imperial College London, said:

“Many of the ocean threats discussed in the report are a direct consequence of excess greenhouse gases in the atmosphere. To address these issues, we must reduce carbon dioxide emissions now.

“While engineering solutions are sometimes proposed in the hope of treating one symptom or another, these are for the most part false-good ideas, costly remedies advocated for by people who do not understand the whole problem. Better to cure the carbon disease directly than try to treat each symptom of the disease as they appear. The ocean is critically under-sampled, under-explored and under-studied; the more we look, the more symptoms we find. However, the more we look, the more reasons we find also to protect it.

“Thankfully, some problems, such as overfishing, have easy solutions.  Overfishing could be immediately addressed through simple policy making, better management, setting up marine protected areas, and a will to enforce these rules. That latter point is key.”

Dr Helene Hewitt, head of the Ocean Modelling group at The Met Office, said:

“With increasing climate change, it is becoming extremely hard for the planet to retain its naturally-occurring reservoirs of ice – known to climate scientists as the cryosphere.

“Meltwater from glaciers and ice-sheets entering the ocean has now become the dominant source of global sea level rise, overtaking the thermal expansion of water as the principal driver of rising sea levels.

“Under all greenhouse gas emission scenarios, sea levels are expected to continue rising. Although projections show there is an obvious reduction in rise following the greatest cuts in emissions.

“Today’s report makes a very strong link between future rises in sea levels and increased coastal flood risk with extreme sea level events that are historically rare becoming more common by 2100.

“Around the UK coasts, UKCP climate projections show that sea levels will continue to rise, with a possible increase in London of 115cm under the worst-case greenhouse gas emission scenario by 2100.”

Prof Jonathan Bamber, Director of the Bristol Glaciology Centre at the University of Bristol, said:

“The evidence is clearer than ever that most parts of the cryosphere and oceans are responding to anthropogenic-driven global warming and this is evident in this latest IPCC report.

“The result is that ice is going to disappear faster than ever: some mountain regions such as the Alps could be almost completely deglaciated by 2100. Sea level rise is projected to continue whatever the emission scenario and for something like business-as-usual the future for low lying coastal communities looks extremely bleak. The consequences will be felt by all of us.

“No one who has been paying attention needs another wake-up call about how bad things could get but, if they did, there is plenty to be concerned about for the future of humanity and social order from the headlines in this report.”

Dr Kate Hendry, Associate Professor of Geochemistry at the University of Bristol, said:

“The polar regions are the most rapidly changing places on Earth, with some parts warming at rates about double that of the global average. In the Arctic for example, the sea ice has retreated rapidly, and there’s less-and-less multi-year ice; the Arctic ocean warmed and acidified, nutrient cycling is changing, and the marine ecosystem is in transition. Each of these changes has direct consequences for the Indigenous populations, and exert influences worldwide through climatic and socio-economic drivers. There is a pressing need to understand how land ice, sea ice and the oceans are interacting under future scenarios, and the potential impact of these fundamental changes in global climate, productivity and economies on human populations both locally and globally.

“The new IPCC SROCC Summary for Policy Makers document is going to be a critical source of information for scientists on the policy-relevant questions surrounding changes in the Arctic and Antarctic, and the “third pole” mountain glaciers. As scientists, it’s going to be essential for us to align our own priorities to answer these questions, as shifts in polar systems are accelerating. Importantly for UK science in particular, the SPM release is coincident with the launch of our new polar research vessel, the RRS Sir David Attenborough; the marine science and glaciology communities need to identify the key policy-relevant research targets for this new capability.

“However, we – as scientists – should no longer work in our ‘silos’. Collaboration between scientific disciplines and between countries is going to be essential to face the logistical and geopolitical challenges ahead. And the scientific community is recognising this reality.

“In recent years, there have been more large, multinational programs to understand the Arctic and Antarctic, embodied by the ice-drift projects led by Norwegian Polar Institute in 2015 (the Norwegian Young sea ICE cruise, N-ICE2015) and the ongoing Multi-Disciplinary drifting Observatory for the study of Arctic Climate programme (MOSAiC) led by the Alfred Wegener Institute in Germany. These programs – gargantuan endeavours to understand seasonal and spatial variability in the Arctic Ocean – are only possible through international and cross-discipline collaboration. With such effort and cost (ships, research stations, satellites, robotics) it’s more crucial than ever that we that we fill in the most important gaps in our knowledge by addressing the questions that really matter to humanity.”

Special Report on the Ocean and Cryosphere in a Changing Climate (SROCC) was published by the IPCC at 10am UK time on Wednesday 25 September 2019.

Declared interests

Dr Hewitt is a coordinating lead author on the IPCC’s upcoming Sixth Assessment Report (2021)