After all, haven’t we already figured that out? It turns out that obtaining a complete picture of how our oceans have been changing is not a simple task, yet is vital for making future projections. In a paper published in Nature this week, my research group developed a more accurate yardstick for measuring rising sea levels, offering clues to a discrepancy that scientists have grappled with for years and potentially insight into future projections of the rise in sea levels.
Sea-level observations over the 20th century come from tide-gauge records, which, in their simplest form, are essentially yardsticks attached to coastlines around the world. The global coverage of these measurements is limited, particularly at the start of the 20th century and in the southern hemisphere. Additionally, even the most complete records can include significant gaps in time. The incompleteness of these records makes obtaining estimates of global mean sea level very difficult.
The latest report from the Intergovernmental Panel on Climate Change (IPCC) included two different estimates of the global increase in sea level over the 20th century. The first estimate came from a suite of previously published studies that analyzed the tide-gauge observations directly. The 1901-1990 rate obtained using these approaches falls in the range of 1.5 to 2 millimeters per year.
The second estimate was computed by adding estimates from individual sources, such as melting water from ice on land and expansion of the ocean. This “bottom-up” approach produced a lower rate of 1 to 1.2 millimeters per year over the same time period.
Explaining the difference between these two different estimates has been a pressing issue within the sea-level community. Most scientists believe the higher estimate derived from tide-gauge records, but they have questioned the lower “bottom-up” estimate.
One possible explanation is that estimates of Greenland and Antarctic melting over the century may have been underestimated. Measurements of ice sheet mass balances have traditionally come from ground-based measurements and satellite observations. However, these observations are also very limited.
That’s when we started to ask ourselves whether or not it was possible to use sea-level observations to try to estimate how much individual ice sheets and glaciers have been melting. Could we use tide-gauge observations over the 20th century to infer how individual contributions combine to produce the global increase in sea levels?
Addressing this question turned out to be much more challenging than any of us initially thought. The physics that allows us to tackle this problem comes down to understanding why sea level at one tide gauge is different than sea level at another.
There are a variety of factors that affect local sea level measurements. These include ongoing effects due to the last ice age, heating and expansion of the ocean due to global warming, changes in ocean circulation and present-day melting of land ice.
All of these processes produce unique patterns, or “fingerprints,” of sea-level change that we can model and predict. Our goal has been to infer the individual contributions to sea level by looking for these fingerprints in the tide-gauge records. This type of “fingerprinting” analysis had been applied to paleo sea-level records, but no one had attempted to look for these predicted patterns in 20th-century sea-level observations.
Developing a way to fingerprint modern sea-level records involved drawing on data analysis and statistical techniques common in other fields such as engineering, economics and meteorology. We brought together these techniques and applied them, for the first time, to the field of sea-level research.
Essentially, our method extracts global information from the limited local observations. Once we began applying our statistical approach to tide-gauge records, we realized that we could add all of our estimated individual contributions to produce a record of global mean sea-level change over time. We assumed that our estimate would agree with the previously published results, but what we found was actually quite different.
The results of our analysis show that the previous estimate for 1901-1990 was too high. We estimate a 1901-1990 “sea-level rise” rate of 1.2 millimeters per year, down from 1.5 millimeters per year. In fact, our lower estimate agrees with the “bottom-up” approach presented in the IPCC. It closes “the sea-level budget” gap by eliminating the discrepancy between the two different types of measurements.
While this may initially appear to be a positive result – that the rise in sea levels was slower last century – it isn’t necessarily. When we look at sea-level rise in the last few decades, we find that our 1993-2010 rate of 3 millimeters per year agrees with previously published results. Using our model, this means that the rate of global sea-level rise has increased not by a factor of two (three divided 1.5 millimeters per year) but rather by a factor of 2.5 (three divided by 1.2 millimeters per year).
That implies that the rate of global sea-level rise is 25% higher in recent decades – a substantial increase. And this revision may affect projections of future sea-level rise.
By Carling Hay, Harvard University
This article was originally published on The Conversation.
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This in the year that the UN climate change circus will pitch its tents in Paris. December’s Conference of the Parties will be the first time individual nations submit their proposals for their carbon emission reduction targets. Sparks are sure to fly.
The research, published in the journal Science, should focus the minds of delegates and their nations as it lays out in authoritative fashion how far we are driving the climate and other vital Earth systems beyond any safe operating space. The paper, headed by Will Steffen of the Australian National University and Stockholm Resilience Centre, concludes that our industrialised civilisation is driving a number of key planetary processes into areas of high risk.
It argues climate change along with “biodiversity integrity” should be recognised as core elements of the Earth system. These are two of nine planetary boundaries that we must remain within if we are to avoid undermining the biophysical systems our species depends upon.
The original planetary boundaries were conceived in 2009 by a team lead by Johan Rockstrom, also of the Stockholm Resilience Centre. Together with his co-authors, Rockstrom produced a list of nine human-driven changes to the Earth’s system: climate change, ocean acidification, stratospheric ozone depletion, alteration of nitrogen and phosphorus cycling, freshwater consumption, land use change, biodiversity loss, aerosol and chemical pollution. Each of these nine, if driven hard enough, could alter the planet to the point where it becomes a much less hospitable place on which to live.
The past 11,000 years have seen a remarkably stable climate. The name given to this most recent geological epoch is the Holocene. It is perhaps no coincidence that human civilisation emerged during this period of stability. What is certain is that our civilisation is in very important ways dependent on the Earth system remaining within or at least approximately near Holocene conditions.
This is why Rockstrom and co looked at human impacts in these nine different areas. They wanted to consider the risk of humans bringing about the end of the Holocene. Some would argue that we have already entered a new geological epoch – the Anthropocene – which recognises that Homo sapiens have become a planet-altering species. But the planetary boundaries concepts doesn’t just attempt to quantify human impacts. It seeks to understand how they may affect human welfare now, and in the future.
It’s been a stable 11,000 years.
Steffen et al
The 2009 paper proved to be very influential, but it also attracted a fair amount of criticism. For example, it has been argued that some of the boundaries are not in fact global in scale. There are very large regional variations in consumption of freshwater and phosphorus fertiliser pollution, for instance.
Phosphorous pollution in croplands.
Steffen et al
That means that while globally we may be in the green, there could be an increasing number of regions that are deep in the red.
The latest research develops the methodology so that it now includes regional evaluations. For example it assesses basin-level freshwater use and biome-level species extinction rates. It also includes a new boundary of “novel entities” – new forms of life and novel compounds the likes of which the Earth system has not experienced and so impact of which is extremely challenging to assess. Ozone-depleting CFCs are perhaps the best example of how a seemingly inert substance can produce planetary damage.
Tree cover remaining in the world’s major forest biomes.
Steffen et al
The paper also gives an update on where we stand on some of the planetary boundaries. At first sight, it looks as though there may be some good news in that climate change is no longer in the red. But then closer inspection reveals that a new yellow “zone of uncertainty with increasing risk” has been added to the previous green and red classification.
2/9ths into the red.
Steffen et al
Climate change impacts are firmly within this new yellow zone. Our atmosphere currently has about 400 parts per million (ppm) of carbon dioxide. To recover back to the green zone we still need to get back to 350ppm – the same precautionary boundary as before.
Perhaps most importantly the research produces a two-tier hierarchy in which climate change and biosphere integrity are recognised as the core planetary boundaries through which the others operate. This makes sense: life and climate are the main columns buttressing our continual existence within the Holocene. Weakening them risks amplifying other stresses on other boundaries.
And so to the very bad news. Given the importance of biodiversity to the functioning of the Earth’s climate and the other planetary boundaries, it is with real dismay that this study adds yet more evidence to the already burgeoning pile that concludes we appear to be doing our best to destroy it as fast as we possibly can.
Extinction rates are very hard to measure but the background rate – the rate at which species would be lost in the absence of human impacts – is something like ten a year per million species. Current extinction rates are anywhere between 100 to 1000 times higher than that. We are possibly in the middle of one of the great mass extinctions in the history of life on Earth.
By James Dyke, University of Southampton
This article was originally published on The Conversation.
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According to Pew Research, 72% of internet users in the US search for health information. In the UK, the Office for National Statistics said health made up 43% of searches in 2013. The empowering of patients to understand and manage their own health is an important issue at a time when departments are under increased pressure.
The NHS is keen to encourage the public to take better care of their health, to know how to spot the early symptoms of bowel cancer for example. But given that inaccurate online information is now just part and parcel of the web, should a universal quality kitemark be applied to good sources to help health consumers make better decisions?
There has been no shortage of articles written about the problems of accessing poor health information on the web. One paper in the Lancet in 1998 quoted a US public health official as saying: “Trying to get information from the internet is like drinking from a fire hose, and you don’t even know what the source of the water is.” Seventeen years on this problem still remains.
Many people – and patients – don’t realise the origins of some of this health information, just that it was on the first page of Google’s search results. This equates to the idea that a page-rank relates to quality, yet many good health organisations and charities don’t have the resources to optimise their search results position.
All too often searches take users to results such as Yahoo Answers, or some spurious website that claims to sell the product from an online snake oil salesman that can cure them of their ailments. Their existence proves there is very much a market for health cures that have no clinical evidence as to their effectiveness.
Very little attention is also paid to factors such as authorship, web links, date of publication, who is behind the website and whether they have ties to commercial companies. Web 2.0 and social media not only allowed consumers to find information on the web and discuss it, but made it far easier for anyone with a motive to publish, a potentially dangerous scenario in a healthcare context.
There are high-quality health information websites that offer comprehensive services from symptom checkers to peer-support groups. Despite this, the issue still remains, that aside from those like NHS Choices and Boots WebMD how do patients know which websites to trust? Comprehensive health websites built on knowledge and impartiality such as Patient.co.uk and Netdoctor and, in the US, the Mayo Clinic, vie for attention among the many forums, blogs and websites providing inaccurate and potentially harmful information.
So what can be done to give users more trust in particular websites? The NHS could encourage users to access and critique good health information – the NHS have already done this by targeting marketing towards specific health groups. Then there is The Information Standard – a certification programme run by NHS England for organisations who produce evidence-based healthcare information for the public. This could also be more widely spread to online content and promoted. Gaining the kitemark requires that information is clear, accurate, balanced and up-to-date.
Another non-for-profit organisation that tries to separate the good from the bad, similar to The Information Standard, is Health on the Net. HON were founded 20 years ago in Geneva and also provide a kitemark for quality information on the web.
The problem for both of these certifications is that most patients are probably not aware of them, despite The Information Standard certifying 250 health-related websites and HON 5,000. And a small badge at the foot of a web page means users are no more likely to be pay heed than to the terms and conditions of Facebook.
Digital literacy remains a big challenge in modern society. Many socio-economic groups are either excluded from using the web or do not have the level of skills to critique and assess online information. Applying quality standards or kitemarks on a site can only do half of the job. In an age where web users become increasingly impatient to find information it becomes also becomes increasingly important for them to have clear signposting.
For patients already in contact with services, front-line healthcare staff – perhaps with some training – could help to teach patients how and where to find the best information about their conditions and symptoms and how to critique the results they find.
Health consumers all want different things from the web, some search for health information for assurance, others for discussion, some for answers and knowledge. Official health campaigns encouraging people to be aware of potential symptoms is good, but teaching them where to access good information for multiple conditions any time is surely better.
At least through a programme of information education and the development of UK health web standards not unlike the Health on the Net organisation, patients could confidently gain a better understanding of their symptoms and conditions and use this knowledge to improve their health.
By Andy Tattersall, University of Sheffield
This article was originally published on The Conversation.
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