Search Results for Tag: Sea level
Can we still avert irreversible ice sheet melt?
Earlier this week, I was able to follow up my last talk with Professor Stefan Rahmstorf from the Potsdam Institute for Climate Impact Research (PIK), after he returned from the Paris climate science forum. After the publication of the study he was involved in on paleoclimatic data linking global temperature with sea level rise, and having heard his views on the science consensus ahead of the December UN summit in Paris, I wanted to know how he views the prospects for the polar ice sheets.
A question I return to often is whether anything we do to reduce emissions from now onwards – given that huge damage has already been done by our fossil fuel emissions and that the CO2 will remain in the atmosphere for a very long time to come – can prevent the ice sheets in the Antarctic and Greenland from reaching a “tipping point”.
Professor Rahmstorf gives this definition of a “tipping point” – which can mean different things to different people in different contexts:
“Climate tipping points are points of no return, where you cannot stop a process that has been set in motion. It’s a bit analogous to the situation where you are sitting in a rowing boat and you lean over a bit to one aside and not much happens. Then you lean a bit more and a tipping point comes where the boat simply tips over. One of these points of no return is with our continental ice sheets, where their further melt-down becomes inevitable and unstoppable. And we have to realize that we have enough continental ice on this planet to raise global sea level by more than 60 metres. That means we cannot afford to lose even a very small fraction of that ice without drowning coastal cities and small island nations.”
Is the boat still afloat?
But, of course, we are already losing ice at a worrying rate. Rahmstorf cites recent research showing that at least a part of the West Antarctic ice sheet has already been destabilized.
“We probably have already crossed the tipping point for a part of West Antarctica. That is probably going to already commit us to about three metres of sea level rise.”
Of course this is not likely to happen in the very near future. But the problem with the tipping points is, of course, that there is no going back, as Rahmstorf explains:
“Sea level has already risen 20 centimetres globally since the late 19th century, due to modern global warming, which is very basic physics. It’s melting continental ice sheets. And also the oceans are being heated up, which expands the ocean water, because warm water takes up more space. And by the year 2100, with unmitigated emissions, we are looking at one meter of sea level rise, which already, for vulnerable coastal areas like delta regions, like Bangladesh for example, will dramatically increase the storm surge risk. But sea level rise will not stop in the year 2100, because the ice sheets are actually quite slow to melt, and within the next decades, we will be causing a long-term sea level rise commitment by several metres for every degree of global warming that we cause.”
Greenland – and Miami, St. Petersburg, Bangladesh…
Record melting appears to be happening on Greenland at the moment. I asked Rahmstorf how safe the world’s biggest island and the largest area of freshwater ice in the northern hemisphere (See also the Ice Island in Pictures) is from reaching a point of no return. He wasn’t able to give a reassuring answer:
“We don’t know exactly where the tipping point is for the Greenland ice shield is. The IPPC estimates anywhere between one and four degrees of global warming. We are already at one degree warming, so we may well cross that tipping point in the next decades.
In the review of the relation between global temperature and sea level rise from polar ice disintegration I discussed in the last blog post, Rahmstorf and his colleagues found that just a slight further rise in temperature might equate to a rise in global sea level of up to six metres. I asked him what that would mean for the world right now:
“There would be quite a number of large coastal cities I cannot imagine could still be defended. Think of New York city for example. Or Miami would be one of the first cities to go. St. Petersburg, Alexandria, Manila – you name them. Once you are talking about metres of sea-level rise, the consequences would be quite catastrophic. Especially as it is to be feared that people will not react proactively by move away from the danger zone, but will probably stay in their cities until a major storm surge hits. Like Hurricane Katrina hitting New Orleans, which also was a case where experts had warned for a long time that the city was in danger, once the next hurricane strikes, but people still didn’t act according to the precautionary principle. As they should have, and as we must do to prevent a climatic disaster in future.”
Can we keep the ice chilled?
So what would we have to do to keep sea level in check?
“Emissions would have to be close to zero by mid-century, so we are not talking about small cosmetic adjustments, but a transformation of our energy system, decarbonization, that is getting out of the carbon-based energy system. The good news is that the technologies to do that are available. It’s all about mustering the political will. And, of course, fighting the particular interests which are opposing this transformation.”
Stefen Rahmstorf is not one of those scientists who prefer to sit on the fence and leave the interpretation of his research and their implications up to the politicians. He is convinced only rapid action to stop emissions can prevent catastrophic climate change – including the melt of the polar ice.
I have interviewed him on previous occasions in the last few years. This time, I was surprised by his optimistic stance on whether the international community can still do anything in time to stop global warming from reaching the dangerous level of two degrees (or even one point five, as Rahmstorf and others say would be far preferable):
“There’s still a good chance that a strong agreement coming out of the Paris summit in December could mean we could avoid the Greenland tipping point. I am cautiously optimistic that Paris will reach a meaningful agreement, not necessarily one that guarantees that we will stay below two degrees global warming, but one that will be seen in hindsight as a real turning point, from where emissions started to fall soon after. The key point is – the sooner we stop global warming, the better the chances are that we avoid future critical tipping points.”
All we need, says Rahmstorf, is the political will to make use of the technologies available, take on the fossil fuels lobby, and clean up our energy system.
Listen to my interview with Stefan Rahmstorf on DW’s Living Planet this week.
DateJuly 17, 2015 | 2:57 pm
TagsAntarctic, Arctic, Climate, Greenland, ice, irreversible ice melt, PIK, Rahmstorf, Sea level, tipping points
Polar ice set for six-metre sea level rise?
Small increases in global average temperature may eventually lead to sea level rise of six metres or more, according to evidence from past warm periods in Earth’s history.
That was the worrying message from a paper published in the journal Science this week. The researchers, part of the international “Past Global Changes” project, analysed sea levels during several warm periods in Earth’s recent history, when global average temperatures were similar to today or slightly warmer – around 1°C above pre-industrial temperatures.
I was able to talk briefly to one of the authors, Stefan Rahmstorf from the Potsdam Institute for Climate Impact Research (PIK), who was in Paris at the international scientific conference “Our common future under climate change” this week. (The article I wrote on that event, billed as the biggest climate science gathering ahead of the key COP in Paris in December, and the full interview with Rahmstorf are online now).
Rahmstorf described the new study on polar ice sheet disintegration and sea level as “a review of our state of knowledge about past changes in sea level in earth’s history, especially looking at all the data we have on past warm periods, due to the natural cycles of climate – the ice age cycles – that come from the earth’s orbit.”
He went on: ”We have had warmer times in the past, the last one was about 120,000 years ago, and we find that invariably, during these warmer times, the sea level was much higher. It was at least about six meters higher than today, even though temperatures were only a little bit higher, maybe one to three degrees warmer – depending on what period you are looking at – compared to the pre-industrial climate.”
Bad news for coastal dwellers
Not happy reading for anyone living close to the coast, if you look at temperature development today:
“Basically the message is: the kind of climate we are moving towards now – even if we limit warming to two degrees – has in the past always been associated with a sea level several metres higher, which would of course have catastrophic consequences for many coastal cities and small island nations.”
With warming currently on course to reach four degrees and more by the end of this century if greenhouse gas emissions continue on their present trajectory, this message adds yet another piece of evidence to motivate the world’s governments to come up with a new World Climate Agreement at the UN Paris summit at the end of the year – and to get moving towards a zero-carbon economy asap.
The interdisciplinary team of scientists concluded that during the last interglacial warm period between ice ages 125,000 years ago, the global average temperature was similar to the present, and this was linked to a sea-level rise of 6 to 9 metres, caused by melting ice in Greenland and Antarctica. Around 400,000 years ago, when global average temperatures were estimated to be between 1 to 2 degrees Celsius higher than –pre-industrial levels, sea level reached 6 to 13 meters higher. The lead author of the study, Andrea Dutton from the University of Florida, told journalists global average temperatures were similar to today during these recent interglacial periods, but polar temperatures were slightly higher. However, she stressed: “The poles are on course to experience similar temperatures in the coming decades”.
The Arctic is currently warming faster than the global average. IPCC estimates indicate that it could be almost two degrees warmer by 2100 compared with the temperature from 1986 to 2005 – IF the two-degree target is adhered to. Otherwise, it could rise by as much as 7.5°C.
Speed of sea level rise hard to predict
The authors of the study stress that the further back you go (they tried to estimate sea level as long as three million years ago), the more difficult it gets to calculate precisely how high sea level was, given that geological forces push and pull the Earth’s surface and can also cause vertical movement measuring tens of metres. This makes it hard to separate the geological changes in shoreline position from sea level rise caused by polar ice sheet disintegration.
Still, the authors point out that small temperature rises of between one and three degrees were, in the past, like today, linked with magnified temperature increases in the polar regions, which lasted over many thousands of years.
They conclude that even keeping to the overall two-degree warming limit is no guarantee: “Even this level sustained over a long period of time carries substantial risk of unmanageable sea level rise, not least because carbon dioxide remains in the atmosphere for over a thousand years”.
The researchers are not able to say how fast sea levels rose in the past, which would be a key piece of information for planning adaptation. Further research will be necessary for that.
Co-author Anders Carlson of Oregon State University says by confirming that our present climate is warming to a level associated with significant polar ice-sheet loss in the past, the study us providing “perhaps the most societally relevant information the paleo record can provide”.
Carlson heads the PALSEA2 Working Group, hosted by the Past Global Changes (PAGES) project, which used computer models and evidence from around the globe to come up with the conclusions in the study.
Stefan Rahmstorf draws a clear conclusion from the results of this research and other recent studies on instabilities in the Antarctic ice sheet and changes in ocean currents:
“This really calls for limiting warming to 1.5 degrees. And it is still feasible to limit warming to 1.5 degrees. But that requires a much stronger political will than we currently have”.
Still, the Potsdam professor is more optimistic than he used to be that advances in renewable energy and other technologies and growing awareness of the negative impacts climate change is already having around the globe could mean the UN Paris conference at the end of the year will mark a turning point.
Not that he thinks Paris can “do it all”. As you’ll see if you read my interview with him, he is hoping for the start of a process similar to the Montreal Protocol, where the original agreement was not too strong, but worked eventually by toughening up as it went along. Now that would be really good news. He told me it was time to “turn the tide of rising emissions”. Here’s hoping it happens in time to keep the sea level around the world well below that six metres that were there in the past.
DateJuly 10, 2015 | 2:30 pm
Ice paradoxes from pole to pole
Returning after a longish break with little access to news and data, there are several ice and snow stories jumping out of my mailbox at me. I’ve picked out two which those of a skeptical persuasion might say disprove some key climate assumptions, but which actually, in fact, confirm some trends and predictions.
Worrying, but not unexpected, are the latest measurements of the extent of the Arctic sea ice. In February, the experts at the National Snow and Ice Data Center (NSIDC) based in Boulder, Colorado, noted a record for the lowest observed maximum sea ice extent. Although it seems the sea ice did grow at some points during March, the overall for the month was the lowest recorded since satellite measurements began in 1979. The average extent for the month was 14.39 million square km – some 1.13 million square km below the 1981-2010 long-term average. The previous March low of 14.45 million square km was recorded in 2006.
In the Arctic Journal, Kevin McGwin quotes Andy Mahoney, a geophycisist with the Sea Ice Group at the University of Alaska Fairbanks, as saying the irregular pattern, with a kind of “double dip”, with the ice decreasing, increasing, then decreasing again, is “a pretty unusual event, regardless of the reason”. Normally, the ice levels would increase to the seasonal maximum first in March, then decline.
One reason, Mahoney says, could be the wind blowing ice into the regions where ice growth was observed, according to the NDSIC the Bering Sea, Davis Strait and around Labrador.
No contradiction to climate warming theory
The NSDIC says warm conditions in the Bering Sea and the Russian Sea of Okhotsk contributed to the record low winter ice maximum.
The overall downward trajectory, however, is clear. The brief increase in March is not a sign that the sea ice is recovering. Mahoney told the Arctic Journal parts of Alaska had seen abnormally high temperatures this winter, which was in line with the overall seasonal ice observations.
“What drives the maximum extent is what happens at the margins, and they can grow and retreat due to short-term variants. The conditions in the central Arctic, far from the action, are indicative of the warm year we’ve had in Alaska,” he said. Barrow, on Alaska’s northern coast, far away from the southern margin, for example, saw a lot of broken ice this winter, according to Maloney.
WWF expressed concerned about the latest figures:
“This is not a record to be proud of. Low sea ice can create a series of reactions that further threaten the Arctic and the rest of the globe,” said Alexander Shestakov, Director, WWF Global Arctic Programme.
“This chilling news from the Arctic should be a wakeup call for all of us,” said Samantha Smith, the leader of WWF’s Global Climate and Energy Initiative. She stresses the need to cut global emissions to halt the Arctic melt.
The proportion of thick Arctic ice that lasts multiple years has dwindled over the past two decades. A recent study shows that Arctic sea ice has thinned by 65 per cent since 1975, leaving ice that is more susceptible to melting.
Writing for Alaska Dispatch News (AND), Yereth Rosen notes that the most dramatic changes in the Arctic sea ice extent have been in the melt season, not in the period of maximum winter coverage. He quotes NSIDC scientist Julienne Strove, who led a study published last year in Geophysical Research Letters which showed the open-water season is lengthening, mostly because of extended melt in summer and autumn. So is this additional winter record a sign of more melting to come? Only time will tell, but the signs are not looking good.
A story from the opposite pole has also attracted attention. It says climate change is actually increasing the amount of snow in the Antarctic. Puzzling? Not necessarily.
More heat, more snow?
An international study headed by Germany’s Potsdam Institute for Climate Impact research (PIK) comes to the conclusion that every degree of regional warming could increase snowfall there by around five percent. The estimate is based on ice cores and climate modeling.
The information adds a new element to calculations of how much the Antarctic will contribute to global sea level rise. Some people might assume more snow would stop the Antarctic from losing mass. In fact the increasing weight of new snow and ice can make it slide towards the coast and into the ocean faster. In this connection, you might like to read some more stories on these Antarctic issues:
Anders Levermann, one of the new study authors, whom I have spoken to several times on the effects of climate change on the Antarctic and global sea levels, says the latest results back up earlier conclusions that the Antarctic will lose more ice than it will gain and thus have a major influence on global sea level. Levermann, from PIK, is also one of the lead authors of the sea-level chapter of the IPCC report. He stresses that the latest study just provides yet another piece of the “jigsaw puzzle” coming together on how global sea level is likely to develop in the future.
If the world leaders called on to come up with a new world climate agreement at the end of this year need any more motivation, this scientific research from both ends of the world should really give them an extra push.
DateApril 10, 2015 | 3:01 pm
The Arctic on the UN agenda
To those of us who deal with the Arctic on a regular basis, the significance of the melting ice for the UN climate negotiations and vice versa is abundantly clear. But not everybody understands all the connections. A major media event like this week’s New York climate summit hosted by the UN Secretary General Ban Ki Moon in person was a fine chance to focus attention on the need to protect the Arctic. Greenpeace made good use of it, handing over a petition with six million signatures just ahead of the big event, and with hundreds of thousands gathered in New York for the Climate March.
It was timely in more ways than one, just as the latest sea ice figures were published to confirm the melting trend.
The petition calls for long-term protection of the Arctic, with the region warming more than twice as fast as the global average and opening the high north to shipping and commercial exploitation. Greenpeace and other groups are calling for a ban on oil exploration, which could endanger the fragile ecosystem. Experts also have safety concerns about increased shipping.
Commercial development versus environment
Earlier this month, a survey showed that 74% of people in 30 countries support the creation of a protected Arctic Sanctuary in the international waters surrounding the North Pole. The study was commissioned by Greenpeace and carried out by Canadian company, RIWI. Around the same time, the Arctic Council, which combines the Arctic states and indigenous peoples’ representatives, currently chaired by Canada, supported the founding of a new business grouping, the Arctic Economic Council. Its aim is to promote the commercial development of the Arctic region. I wrote about this here on the Ice Blog and on the DW website.
Global responsibility for the Arctic
The UN Secretary General accepted the Greenpeace petition saying:
“I receive this as a common commitment toward our common future, protecting our environment, not only in the Arctic, but all over the world.”
Ban Ki-moon said he would consider convening an international summit to discuss the issue of Arctic protection. He also expressed a desire to travel aboard one of the organisation’s campaigning ships in the Arctic in the near future.
Greenpeace Executive Director Kumi Naidoo, who was part of the delegation, said: “The Arctic represents a defining test for those attending the summit in New York”.
He said leaders should bear in mind that concern for the rapid warming of the world was not consistent with planning oil and gas development in the melting Arctic.
The small delegation that met Ban Ki Moon included Indigenous rights activist and Saami politician Josefina Skerk, who last year trekked to the North Pole to declare the top of the world ‘the common heritage of everyone on earth’.
Skerk, a member of the Saami Parliament, said: “We, who want to continue living in the North, are gravely concerned about climate change and the destructive industries that are closing in. My people know and understand the Arctic, and it is changing in a manner, which threatens not just our survival, but the survival of people all over the world.”
Skerk said humans had created the crisis and had to take action to solve it.
“I urge the Arctic countries in particular to take a giant step up and I think the world needs to pay much closer attention to ensure that it happens. They might as well start here in New York.”
From Kiribati to Svalbard and New York
Melting ice especially from the Arctic Greenland ice sheet is raising sea levels around the globe, endangering low-lying areas. At the weekend, the President of Kiribati, Anote Tong, ended a Greenpeace-organized tour of glaciers in Norway’s Svalbard Archipelago. He said the trip to the Arctic ice had made a deep impression on him, which he would share with world leaders at the U.N. climate summit:
“It’s a very fascinating sight. In spite of that, what I feel very deeply is the sense of threat,” Tong said. “If all of that ice would disappear, it would end up eroding our shores.”
Kiribati is a group of 33 coral atolls located about halfway between Hawaii and Australia. Many of its atolls rise just a few feet above sea level.
In last year’s report by the Intergovernmental Panel on Climate Change (IPCC), experts concluded oceans could rise by as much as 1 meter (3.3 feet) by the end of this century if no action is taken to cut the greenhouse gas emissions causing global warming.
“It won’t take a lot of sea level rise to affect our islands,” Tong said. “We are already having problems.”
Sea ice minimum confirms melting trend
The New York summit coincides with the annual announcement of the minimum sea ice for the year, as the summer season comes to an end. The sea ice – in contrast to glaciers on land – does not influence global sea level, but is regarded as a key indicator of how climate change is affecting the region. This year the figure announced by the US National Snow and Ice Data Centre (NSIDC) was 5.01 million square kilometers. The figure is the sixth lowest extent since records began.
The minimum ever recorded at the North Pole was 3.29m sq km in 2012 – and the eight lowest years have been the last eight years.
Ice levels in the Arctic have recovered from their all-time low, but are still on a shrinking trend, said Julienne Stroeve of the National Snow and Ice Data Centre. ”We have been telling this story for a long time, and we are still telling it,” she said.
NSIDC records showed that, this year, ice momentarily dipped below 5million sq km to 4.98m on 16 September, but the official figure is taken from a five day average.
Satellite data shows that one part of the Laptev Sea was completely clear from sea ice for the first time this summer. One of the most important questions for climate scientists is how soon the Arctic will experience its first sea ice-free summer.
Rod Downie, head of WWF UK’s polar programme, said that this year’s new Arctic minimum should prompt new action from the leaders meeting in New York. He stressed the connection between the Arctic and weather conditions in other parts of the world:
“As David Cameron prepares to meet other global leaders at the UN climate change summit in New York, the increased frequency of extreme weather that is predicted for the UK as a result of a warming Arctic should serve as a reminder that we need urgent action now to tackle climate change,” he said.
The summit was a major PR event to draw attention to the need for urgent and substantial climate action. The accompanying protests around the globe show people are not happy with the slow pace of the climate talks and their governments’ efforts to reduce emissions. Of course there was little in the way of concrete pledges. Still, on the whole, I see it as a successful step on the way to a new climate agreement because it has put the spotlight on climate change at a time where international conflicts are dominating the news agenda.
More commentary on the summit from me here:
DateSeptember 24, 2014 | 2:22 pm
TagsArctic, Ban Ki-Moon, Climate, CO2, Emissions, Greenpeace, ice, New York, sea ice, Sea level, UN, UN talks, WWF
Polar Ice at UN Bonn Climate Talks
The delegates to the UN climate meeting currently taking place here in Bonn are receiving an urgent appeal from polar scientists to cut emissions to slow polar ice melt and give low-lying coastal regions more time to adapt to rising sea levels.
I was very interested to hear about a side-event being held here this evening, at which the authors of this year’s key studies on developments in the Antarctic will be explaining the connections between melting polar ice and climate change impacts like rising seas, affecting regions as diverse as small island states, Bangladesh or Florida in the USA.
I interviewed Anders Levermann from PIK, the Potsdam Institute for Climate Impacts Research and Pam Pearson, Director of ICCI, the International Cryosphere Climate Initiative, both in Bonn for the event.
The ICCI decided to bring the cryosphere into the Bonn talks to sensitize delegates to the dramatic developments in the Antarctic in particular, says Pearson. Ice Blog readers (and I was so delighted to hear Pam herself is one!) will remember posts earlier this year on melting in the East and West Antarctic. I also covered these in articles for DW. The shocking thing is that the Antarctic, even East Antarctica, which was until relatively recently considered so cold it had to be safe from global warming, is already being affected by climate change. The papers on the West Antarctic even described the melt trend as “irreversible”.
“We have entered an era of irreversible climate change”.
Today, Anders Levermann, author of the East Antarctic paper and one of the world’s leading Antarctic researchers, told me “we have entered a new era of climate change, witnessed the tipping of the West Antarctic ice sheet, and this is irreversible”.
That should really shock people into action, you would think. But climate negotiations are moving, as one of the experts said to me at the meeting “at a glacial pace”. As we can see in Antarctica, though, and Greenland and other regions, those glaciers are speeding up. Maybe there is hope for the climate talks yet!
The announcements by the USA and China on possible emissions cuts have brought a new “buzz” to the Bonn conference. The fact that the key emitters could finally be getting the message and preparing to move, with the impacts of climate change hitting their own countries, has to be a positive signal. Pearson confirmed to me that people in the sunshine state of Florida, where she lives, had become more aware of the importance of melting ice caps with increasing floods and storms.
As Levermann says, Antarctica and Greenland have a huge potential to raise sea level further than previously anticipated. He was lead author on the IPCC report chapter on sea level rise. The latest IPCC report factored in some of the likely impacts from melting ice in these regions for the first time. Of course the latest research was not yet included. For the 21st century forecast, this will not make a lot of difference, says Levermann. But the fact that this irreversible Antarctic melt is now underway will make a big difference to coming generations.
There are those who dispute whether the warming of the ocean, which is causing the Antarctic melt (unlike the surface melt on Greenland) is man-made. Levermann does not rule out natural variation as a possible influence. But ultimately, he says, that is irrelevant. Greenhouse gas emissions and so human interference are warming the planet, and any further warming, whatever the cause, will speed up ice melt. So cutting emissions is the way to slow it down and, Pearson adds, gives people time to adapt to rising seas.
The combination of models based on the principles of physics, using a higher resolution than ever before, and evidence from ice cores showing what happened in the past, make for a high degree of certainty about these ice developments, says Levermann.
“The level of warming will determine the rate with which we discharge West Antarctica, and we can still prevent the tipping of East Antarctica”, the cryosphere experts told us here in Bonn.
That is a huge responsibility. Here’s hoping the message will make it into the hearts and minds of those negotiating the future of the earth’s climate and the governments they represent.
DateJune 13, 2014 | 2:34 pm