The Liverpool View: Climate change threat is real

Dr Hannah Levis, Reader in Ophthalmic Bioengineering, Eye & Vision Sciences

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Phil Woodworth is a visiting Professor in the University of Liverpool’s School of Environmental Sciences

“Last week saw the publication of the 5th Assessment Report of Working Group I of the Intergovernmental Panel on Climate Change, usually called just the ‘IPCC Report’. The findings extend and strengthen those of the 4th Report six years ago.

The atmosphere and ocean have warmed significantly during the 20th century due to the radiative forcing of greenhouse gases that are unquestionably of human origin. Arctic sea ice is in retreat, ice sheets in Greenland and Antarctica and mountain glaciers on each continent are thinning, and sea level has risen by about 20 cm. Studies suggest that sea level could continue to rise by up to 82 cm for the period 2081-2100 compared to the period 1986-2005, depending on a likely range for the world’s future carbon emissions.

Central importance of oceans

The oceans are of central importance in this research, having absorbed over 90 % of the increase in the energy (heat content) of the atmosphere-ocean system due to the warming. So, questions of how the oceans actually work have never been more important in considering how life on this planet will have to change and adapt in the future. The National Oceanography Centre (NOC), based on the Liverpool campus, and the Ocean Sciences group of the University’s School of Environmental Sciences play important roles in this research, particularly with regard to sea level change.

At NOC, we operate a monitoring system of the level of the seas around UK coasts (www.ntslf.org), including a station at Gladstone Dock at Liverpool which has one of the longest sea level records in the world. This system is designed primarily for the monitoring of wintertime floods, and has existed since the devastating storm surge in eastern England and the Netherlands in 1953. However, the same data collected over many years provide information for research into climate change.

”With the use of sea level data collated at Liverpool, the IPCC 5th Report concluded that global mean sea level has risen at an average rate of 1.9 mm/year since the start of the 20th century”
NOC also has stations for monitoring sea level in the South Atlantic, Antarctica and Gibraltar, all of which are components of the Global Sea Level Observing System. Data from all these stations go into the Permanent Service for Mean Sea Level databank (PSMSL, www.psmsl.org), hosted at NOC, which is the primary source of information on long-term global ‘mean sea level’ change used by the IPCC.

With the use of sea level data collated at Liverpool, the IPCC 5th Report concluded that global mean sea level has risen at an average rate of 1.9 mm/year since the start of the 20th century, but with considerable regional variations linked to the way that the ocean circulation has adjusted. At the coast, the observed sea level change will be a combination of this regional sea level change and change in the level of the land that the observer is sitting on. Land level change can be positive or negative (emergence and submergence) due to regional and local geological processes. For example, in northern Sweden, where the land is still popping up following the removal of the great ice sheets after the last Ice Age, the effects of present-day sea level rise are minimal compared to those of Glacial Adjustment. However, in low-lying areas such as Bangladesh, which is in a submerging river delta, sea level rise is already having major impacts.

SeaLevel-1wCompilations of global sea level (m) estimated from historical and paleo data, and melded with future predictions for low (blue line) and high (red line) emission scenarios. The historical data includes tide gauge data collated at Liverpool (PSMSL) and reconstructions from salt marshes (purple symbols). Reproduced from the IPCC report

For most people who live near the coast, there will be less interest in the slow changes in the mean levels of the ocean taking place on timescales of decades or centuries than in the sometimes dramatic extreme events (storm surges) caused by winter storms. As far as we know, the increase of the extreme sea levels that have occurred during storms during the last few decades have been similar to those in mean sea levels, rather than due to changes in the frequency of the storms themselves. For many parts of the UK coast, the increase in mean sea level during the 20th century (about 20 cm) will have doubled the risk of flooding.

So how much more frequently are you likely to be flooded in future? The answer to this question depends on exactly where you live, and the statistics of tides and storm surges in your area. But, as a general rule, one can say that changes in flood frequency have a logarithmic relationship to mean sea level change.

”For many parts of the UK coast, the increase in mean sea level during the 20th century (about 20 cm) will have doubled the risk of flooding”
Using the above example, if mean sea level changes by 80 cm in the future then that would increase the frequency of flooding by a factor of 24 = 16. In other parts of the world, such as the flat coastal delta of Bangladesh, or coral islands which have elevations of only 1-2 m, then the impacts could be considerably larger. Studies of the likely impacts are the responsibility of the IPCC Working Group II, the final report of which is planned in 2014.

NOC had major inputs to the IPCC 5th Report, providing lead and contributing authors and a review editor to two of its thirteen chapters. The inputs were possible because of the expertise that exists in NOC in Liverpool in Sea Level Science. One of the largest sea level groups in the world is based here, collaborating closely with scientists in the School of Environmental Sciences which has its own expertise in topics such as how the oceans are warming and the mechanisms for exchange of carbon between the atmosphere, land and ocean. In addition, NOC plays an important role in advising on Government policy (Defra, DECC, DfID) on issues such as coastal protection, and has played a major part in studies such as Thames Estuary 2100 in considering how London can continue to be effectively protected from flooding.”

Do you want to know more?

Register at www.psmsl.org for a workshop celebrating the 80th anniversary of the PSMSL, to be held on 28-29 October in the Victoria Building in Liverpool.

This workshop will contain several extensive review talks of the IPCC Report by some of the world’s leading climate scientists.

The following people contributed to this article: Dr Svetlana Jevrejeva (National Oceanography Centre, IPCC lead author for sea level change), Professor Chris Hughes (joint University of Liverpool and National Oceanography Centre) and Professor Ric Williams (School of Environmental Sciences, University of Liverpool)

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3 thoughts on “The Liverpool View: Climate change threat is real

  1. Carl Inist

    I agree with Ric Williams that the IPCC is a substantial ‘exercise’, but that is as far as my agreement goes I am afraid…the exercise is a political one harnessed by the UN to slowly convince the masses of uneducated or unwilling to undertake factual research sheeple that they are responsible for societies ills (largely brought about by capitalist corporations, which seem to wilfully destroy whole ecosystems in the name of the almighty shareholder profit). “Taxation and destruction of rights to occupy certain indigenous lands should ensue in order to save our planet” is the basic rhetoric of the UN. Of course none of the preaching that emanates from the so-called ‘contributing experts’ to the IPCC’s cause (mostly comprised of scientists and politicians feathering their own potentially insignificant nests, if it weren’t for our flagrant disregard for the planet : ) is based wholly on the scientific facts as they stand. The data is manipulated in order to reinforce the point the politicians and scientific scaremongers wish to make. Any factual science presented to the IPCC is ‘cherry picked’ and edited during behind closed doors review processes, prior to anything ever being published. If we take the sea level graph presented in this article for instance it proves my point nicely. We know that we are at present in one of the many interglacial periods that have occurred over the millennia. How? From the varied paleo-scientific proxies used to track the Earth’s climate from time zero until just over a century ago when instrument technology invention and advancements allowed for resolution of data that was once both temporally and spatially sparce to improve hugely. Go back just a few centuries from present and we have the medieval warm period, conveniently discarded from many of the IPCC reports, particularly when Climate Change was known as Global Warming! Even accounting for standard error in estimation of proxy records, mean sea level was greater than it is today (see Dr Jeff Masters Wunderblog). Go back farther to the last Ice Age and sea levels dropped dramatically, back farther still to Mesozoic era’s and sea levels were far higher than they are today. So what do these long timescale perturbations tell us, well that undoubtedly sea levels will rise and fall as long as natural astronomical forcings and internal Earth system feedbacks (in particular linked to the global mass distribution of water in its various states – the IPCC does at least acknowledge that water is the most potent greenhouse gas) conspire to create climate changes. Eureka. However until scientific evidence exists proving unequivocally that the dinosaurs invented the internal combustion engine or that Richard I had a private jet, I fail to see the link between atmosphere and ocean warming of the 20th century due to radiative forcing of GH gas from human origin, especially given that we are also wholly aware that levels of the next most potent GHG’s (CO2 and CH4) have also been proven to be much higher than todays levels in historic records. One must assume without the influence of man made pollution no doubt? And before any ‘rate of change’ arguments are filtered my way, let us wait until we have another comparable interglacial era in the Earth’s ongoing journey with matching analytical resolution in the data before we go preaching any mainstream media type ‘highest since records began’ spiel. As a free, organic being of this Earth, I’m with Colin on this one Professor, cow farts and respiration are not destroying the planet, elitist incapacity to conserve (or financial greed) certainly might be!

  2. Ric Williams

    In response to the comment by Colin Johnson:

    1. The IPCC report is a substantial exercise, involving a total of 209 Lead Authors and 50 Review Editors from 39 countries and more than 600 Contributing Authors from 32 countries contributed to the preparation of Working Group I AR5. Whatever was done for the publicity, this report cannot be dismissed so tritely.
    2. It is correct that aerosols can perhaps partly offset the greenhouse warming, which is why volcanic emissions often lead to short term cooling, part of the reason for fluctuations in the warming of the planet.
    However, whether we wish to live in a smog-covered planet is another matter.
    3. There are still serious questions about how climate change and variability are operating. However, some very basic physics and chemistry predicts more carbon dioxide (like other triatomic gases, such as water vapour) lead to a warmer surface temperature. There is no other serious explanation of why the planet has warmed over the last 50 years, why the Arctic summer sea ice and many glaciers are retreating, and why global sea level is rising. So while some people prefer to ignore the advice of experts, there are serious risks in doing so.
    4. Taking another health analogy, forty years ago there was a similar campaign, drawing on the advice of experts, that smoking was harmful to your health, now we are starting to see the benefits of that health policy. In a similar way, we need to be thinking of how we want the planet to be in 40 years time.

  3. Colin Johnson

    If I recall correctly was it not the IPCC that used summer photographs of melting ice flows, polar bear as an extra, but claimed them to be winter shots, to justify and inflate their argument on climate warming. With stunts like that how are we supposed to trust “proffesional” guidance. I am not really into the global warming movement but I think I overheard a comment by an enviromentalist on a program on the television this past week where she commented the burning of fossil fuels caused polution which ‘bonded’ with water vapour in the atmosphere to cause a smog screen which would sheild the Earth from the Sun’s rays, I would presume if correct then does this indicate we should go back to coal fires to create a global sheild to stop Global warming. Another of my favourite anecdotes relate to the harmful effects of Salt, for years the experts told us it’s harmful you must reduce your intake but now low and behold the experts tell us another study revokes this thinking. Perhaps we should make our own minds up on these matters and take the experts with a ‘pinch of salt’.

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