Select Committee on the Arctic - Report of Session 2014–15

Responding to a changing Arctic


Chapter 2: Climate change in the Arctic

Climate change is altering the Arctic

16.The Arctic is warming, with average surface air temperatures in the region increasing at around twice the global average rate over the past few decades.6 These rises in temperature have had, and if maintained or increased will continue to have, a number of fundamental effects upon the Arctic environment, both on land and at sea. Environmental and climatic changes in the region will generate changes further afield, including impacts which affect the UK and its weather patterns.

17.This chapter considers climate change in the Arctic, and its potential wider environmental and climatic implications. Subsequent chapters reflect upon Arctic opportunities, risks and challenges which result, primarily, from ongoing climate change in the Arctic, which is credited with increasing the accessibility of the region and heightening interest from non-Arctic states and other actors.

18.As this chapter makes clear, our evidence indicated that considerable uncertainty remains, although with a consensus emerging around the dominant trends of warming and climate change amplification. The relationship between climate change and accessibility in the Arctic is not, therefore, straightforward.

Rising temperatures

19.In its Fifth Assessment Report (2013–14), the Intergovernmental Panel on Climate Change (IPCC) reported that the globally averaged combined land and sea surface temperature warmed between 0.65 and 1.06°C from 1880 to 2012.7 The northern high latitudes, however, have experienced greater warming than the mid-latitudes or the southern high latitudes, as demonstrated in Figure 4. This increased warming at high northern latitudes was predicted in the First Assessment Report (1990) of the IPCC.8

Figure 3: Arctic surface air temperature anomaly over land, 1900–2014

Source: Met Office (2015).

Figure 4: Polar amplification of warming in the last decade

Source: Written evidence from the Norwegian Polar Institute (ARC0061), using NASA Goddard Institute for Space Studies data: http://data.giss.nasa.gov.

20.The evidence we received demonstrated that the average temperature in the Arctic had risen at around twice the global mean in recent decades.9 Dr Ed Hawkins of the University of Reading attributed this to ‘polar amplification’:

“As you warm the planet you melt the ice, as we have been seeing. That reduces the reflectivity of the planet so that more energy is absorbed into the oceans rather than reflected out into space, which amplifies the warming that we are seeing … We expect to see amplified warming in the Arctic in the future, and on top of that we will see random fluctuations that are to a degree essentially unpredictable. They will mask or enhance temperature trends at different times in the future. However, we will see an overall warming with an Arctic amplification”.10

21.At most locations, temperatures measured since 2005 have been higher than at any time in the available historical record. Annual average temperatures across the whole Arctic have been consistently around 1.5°C or more higher than they were from 1961 to 1990.11 We were told that winter is warming faster than summer in the Arctic,12 and that land temperatures have increased at a greater rate than temperatures at sea.13

22.The limitations of past projections of Arctic climate change were consistently emphasised in the evidence we received. Dr Jan-Gunnar Winther of the Norwegian Polar Institute, for example, told us that he was “somewhat worried for future projections” and that researchers had, over the past ten years, “consistently and severely underestimated the rate of change”.14

23.Global temperatures have fluctuated during different historic periods; we received evidence explaining various drivers of these changes and the causes of variability.15 We were informed, however, that the scale of recent warming in the Arctic was important for two reasons: pace, and magnitude:

“There have been rapid changes [before]. However … none of them is as rapid or has this magnitude. There are always small rapid changes but this magnitude of change is very large”.16

24.Greenpeace told us that these changes to the Arctic were “both rapid and fundamental. The data from the scientists about the extent and volume of sea ice tell us that the Arctic is in a pretty bad way. The overall trend is worrying”. They went on to state that the overall picture was “pretty stark” and should compel action.17

25.Our principal focus is upon the effects of these changes on the Arctic environment: rising temperatures have significant impacts upon sea-ice coverage, land ice, permafrost and the oceans more generally. These in turn have implications for ecosystem stability and the animal life that the region sustains on land and sea.

The effects of temperature increases in the Arctic

Changes in Arctic sea ice

26.Arctic sea ice cover expands each winter as sunlight is limited, before shrinking each summer as the sun rises higher in the northern sky. Sea ice is usually at its minimum annual extent in September. Since 1979, with the onset of satellite monitoring, it has been possible to obtain more accurate measurements of the extent of sea ice across the Arctic.

Figure 5: Sea ice extent changes, 1979–2014

Source: Met Office (2015).

27.These measurements show that, at the start of the satellite era, the September minimum sea ice extent was typically around 7.5 million km2. Since then, there has been an underlying downward trend (with some year-to-year variability), with a 13.3 per cent loss of coverage per decade.18 This has resulted in an average minimum ice extent, in recent years, of around 4.5 to 5 million km2; a low point of 3.4 million km2 was reached in 2012. The last eight September minimum sea ice extents have been the lowest on satellite record.19 We were told that summer minima could be at their lowest point for 1500 years.20

Figure 6: September 2014 sea ice extent

Source: Derived from US National Snow and Ice Data Centre: https://nsidc.org.

28.The Arctic Climate Impact Assessment (ACIA) report of the Arctic Council21 in 2004 was the first comprehensive assessment of climate change in the Arctic; this was further expanded in the 2011 Snow, Water, Ice and Permafrost in the Arctic (SWIPA) Report. A key finding of the SWIPA report was that observed reductions in sea ice extent in the Arctic had outpaced the projections from scientific modelling, including those used in the IPCC Fourth Assessment Report22 modelling scenarios.

Figure 7: September 1980 and September 2012 sea ice extents

Source: Derived from US National Snow and Ice Data Centre: https://nsidc.org.

29.A reduction in Arctic sea ice extent could have some potentially beneficial implications, including the opening up of new shipping and trade routes and making some northern communities more accessible to destination-based shipping.23 We were told, however, that the relationship between sea ice reduction and economic opportunities was not simple, with the increasing unpredictability brought about by changes to ice coverage being one limiting factor.24

Figure 8: Multi-year sea ice in the Arctic

Source: US National Oceanic and Atmospheric Administration, Arctic Report Card 2013:
http://www.arctic.noaa.gov/report13/sea_ice.html.

30.Extent is only one measure of Arctic sea ice; the thickness of ice is also important, both as a factor in the total sea ice volume (and thereby an indicator of the rate of change) and because of how it relates to the nature of the ice. Estimating ice thickness—and therefore the overall volume of Arctic ice—is more complicated than measuring surface ice extent, as ice thickness varies across the Arctic depending on a range of conditions, and cannot be continuously assessed.

31.Notwithstanding this limitation, we were told that in the 1980s thick multi-year ice, which persists from one summer season to the next, had covered most of the Arctic Ocean. This had, over the years, been largely replaced with thinner and much less resilient ‘first-year’ ice, which forms in the winter but then typically melts in the summer.25

32.Such a change in the thickness of sea ice means that, taken as a whole, the prospect of significant, rapid melting of the ice becomes more likely. We were told that:

“There is a new Arctic emerging with dominantly thin first-year ice; which also tells us that the situation is more vulnerable since it is easier to melt first-year ice. If the conditions are favourable for ice-melting, in theory, most of this sea ice could melt within one season”.26

33.When taken together, the reduction in the thickness of the ice and the reduction in its spatial extent equate to a substantial loss of Arctic sea ice volume. Professor Peter Wadhams of the University of Cambridge told us that “the volume of summer sea ice in the Arctic went down by 75 per cent in the last 30 years … That is a very serious change, and it is unprecedented, at least in the history of observations and given what we know from sediment cores from the history of the Arctic Ocean. It looks like it is heading in one direction only”.27

34.Atmospheric temperatures are an important driver of these changes. Professor Andy Shepherd of the University of Leeds stated that the majority of changes to sea ice witnessed in “the past 50 or 60 years” could be attributed to greenhouse gas emissions and their effect on temperatures in the Arctic region. Prof Shepherd suggested that the length of the solar melt season had increased by around five days per decade, causing additional melting and retreat of the ice.28

35.Temperature is not, however, the only causative factor. Changes in ocean circulation also have an impact: we were told that an increase in warm water coming into the Arctic from the Atlantic, and an increased northwards flow from the Bering Strait were acting to reduce sea ice coverage.29 Ice thickness and extent can vary rapidly in response to weather, with seasonal conditions playing an important role in the minimum extent and spatial distribution of ice at the end of summer. In 2007, for example, persistent winds through the summer stacked up the ice, reducing its area to a new minimum record. In 2012, conditions were less favourable to ice retreat through the summer, but a strong cyclone in early August may have helped to break up the ice and enhance melt, resulting in a further record low.30

36.While September ice extent increased in 2013 to 5.1 million km2,31 partly as a result of unusually cool summer conditions, that is nonetheless the seventh lowest extent since satellite records began.32 We were repeatedly told that, while ice extent would continue to vary from year to year, the underlying long-term trend was undoubtedly downwards.33

37.We were told that the Arctic would be considered ‘ice free’ in the summer when ice coverage is less than 1 million km2, and ‘reliably ice free’ when these conditions persist for five summers or more.34 We explored with our witnesses the projections for when these milestones might be passed. The natural variability of oceanic and atmospheric conditions, coupled with continuing uncertainty regarding the intrinsic physics of sea ice and future temperatures, make precise prediction very difficult.35 The extrapolation of trends is made additionally difficult by limitations on the availability of data from before 1979, and the lack of satellite observations for the entire Arctic before 2010.36

38.Notwithstanding these limitations, we were given a range of estimates as to when the Arctic might be ‘ice free’ and ‘reliably ice free’. At one extreme, Prof Wadhams suggested that trends indicated a complete loss of summer sea ice “somewhere between next year and 2020”.37 Others suggested that there was a possibility of occasional ice-free summers in the next 20 to 30 years.38 There was, however, a general consensus that supported the IPCC prediction of a reliably ice-free Arctic summer by 2050–2080, with variability in trends along the way.39

39.While it is not currently possible to predict accurately when the Arctic Ocean will experience summers that are reliably free of sea ice, it is evident that there is a sharp underlying downward trend in sea ice extent and volume. It is a question of ‘when’ rather than ‘if’ the Arctic will be substantially free of sea ice in summer.

The melting of land ice and reduction in snow cover

40.An ice sheet is a continuous thick glacial land ice mass that covers more than 50,000km2. In the past, huge ice sheets covered Canada and Scandinavia; these disappeared due to historic climate change. At present, the only such example in the northern hemisphere is the Greenland ice sheet, which is 1.7 million km2 in extent, up to 3km thick and several million years old. While the melting of sea ice does not affect sea levels, the volume of ice contained in the Greenland ice sheet would, if completely melted, be sufficient to raise global sea levels by 7.4m.40

Figure 9: Loss of mass in the Greenland ice sheet

Monthly mass anomalies (in gigatonnes, Gt) for the Greenland ice sheet since April 2002, estimated from GRACE measurements. The anomalies are expressed as departures from the 2002–2014 mean value for each month. For reference, orange asterisks denote June values (or May for those years when June is missing).

Source: US National Oceanic and Atmospheric Administration, Arctic Report Card 2014: http://www.arctic.noaa.gov/reportcard/greenland_ice_sheet.html.

41.We were told, unequivocally, that the ice sheet is melting, and that this will contribute to rising sea levels:

“It is a very simple formula: if you warm up the ice on land, it flows straight into the oceans. In Greenland, that has been happening at an accelerating rate. The rate of loss from Greenland has increased by a factor of five over the past 20 years and enough ice is being lost to cause [global] sea levels to rise by about one millimetre per year, whereas in the 1980s the contribution was very slight”.41

42.The Greenland ice sheet is the most significant Arctic mass of land ice, but we were told that ice caps and glaciers across the region were also melting. This melting land ice is flowing, initially, into Arctic waters and thereafter will affect sea levels worldwide.42

43.The Arctic Ocean is currently a carbon sink: at low temperature it readily absorbs carbon dioxide from the atmosphere. Increased freshwater flowing into the Ocean from melting land ice may affect the heat balance of the Arctic Ocean.43 Oceanic circulations might also be affected.44 These feedback loops and cycles are considered in further detail in paragraph 60.

44.In terms of spatial extent, seasonal snow cover is the largest single component of the cryosphere45 and has a mean winter maximum areal extent of 47 million km2.46 On average, across the entire Arctic, the duration of winter snow cover became four days shorter every decade in the period between 1972/73 and 2008/09.47 We were told that snow cover duration reached a record low in 2012.48 The rate of loss of June snow cover extent between 1979 and 2014 was 19.8 per cent per decade, which is greater than the loss of September sea ice extent (-13.3 per cent per decade) over the same period.49

Figure 10: Snow cover changes in the Arctic, 1979–2012

Source: Adapted from C Derksen and R Brown, ‘Spring snow cover extent reductions in the 2008–2012 period exceeding climate model projections’, Geophysical Research Letters, vol 39 issue 19 (2012): http://onlinelibrary.wiley.com/doi/10.1029/2012GL053387/pdf.

The albedo effect

45.Reduced snow cover, the melting of land ice and reductions in sea ice coverage all work to reduce the albedo of the Arctic. Albedo refers to the fraction of solar energy reflected from the Earth back into space, particularly by ice and snow on the surface of the planet. As snow and ice melts, greater extents of darker coloured land and sea are exposed; these surfaces absorb more of the heat of the sun and therefore amplify the effects of warming.50 In other words, loss of snow and ice has not only a direct effect, and impacts on ocean circulation and sea level: it also intensifies climate change by contributing to greater heat absorption.

46.We were told that the amplifying effects of the loss of albedo could have far-reaching consequences. The Arctic Methane Emergency Group told us that recent research had almost doubled the estimate of the effects of albedo loss, and that “The ultimate heat contribution, when the snow and sea ice have disappeared for much of the year, could be equivalent to a doubling of CO2 … Such an addition to the energy balance would kibosh all efforts to keep global warming to a safe level through emissions control”.51

Permafrost melting and infrastructure problems

47.Permafrost is ground that remains frozen for two or more years. IPCC Assessments have consistently highlighted that permafrost will be subject to melting as the Arctic region responds to climate change.52 We were told that, in some parts of the Arctic, permafrost has now disappeared altogether.53 Whilst thawing permafrost can cause some immediate and obvious local impacts, the wider and longer-term effects of this melting are largely unknown and difficult to predict.

48.The most direct indicators of changes in permafrost state are active layer thickness and temperature. The active layer is the top layer of soil and/or rock, sitting above the subsurface permafrost; the active layer thaws during the summer and freezes again during the autumn. In the period between 1998 and 2012 active layer thickness increased across many parts of northern Russia, indicating that more of the permafrost is melting in summer.54 A progressive increase in active layer thickness has also been observed in Nordic countries, including in the Abisko area of Sweden, where permafrost has disappeared altogether from several mire landscapes since 1995.55

49.Permafrost temperature can be used as an indicator of long-term change. In 2013, new record high temperatures at 20 metres of depth were measured at two permafrost observatories on the North Slope of Alaska and in the Canadian High Arctic.56

50.Thawing of permafrost will have local impacts upon infrastructure and the built environment for the foreseeable future, with subsurface movements and melting causing disruption to buildings, pipelines, transport routes and migration routes of animal populations. The 2011 SWIPA report also noted that Arctic ecosystems were affected by habitat changes resulting from permafrost thaw.57

51.Rising temperatures have other impacts on infrastructure: we were told that the period during which ice roads, essential for Arctic land transport in winter months, were usable had reduced by almost two months in recent decades.58 All eight Arctic states are projected to suffer “steep declines” in inland accessibility as a result of lost potential for winter road construction.59

The potential for methane and carbon dioxide release

52.Thawing Arctic permafrost is likely to have global impacts. Frozen soils at higher latitudes are carbon rich as they contain large amounts of dead, but only partially decomposed, plants. As the Arctic warms, however, the frozen soils will melt, allowing micro-organisms to grow. These micro-organisms will break down the plants and release carbon into the atmosphere. This additional carbon in the atmosphere could cause more warming, further melting and, therefore, further carbon release.60

53.Drainage of the thawed zone is very important as the micro-organisms that break down plants work differently in wet and dry conditions.61 If the water drains away, it will allow oxygen into the soils and the micro-organisms will break down the plants aerobically. Aerobic decomposition is rapid and results in CO2 emissions. If water remains and the soils are water logged, this will prevent oxygen entering the soils and the micro-organisms will break down the plants anaerobically. Anaerobic decomposition is slower but results in methane emissions. Methane is a considerably more potent greenhouse gas62 than CO2 and concern has been expressed regarding the long-term implications of methane release for further regional and global warming.

54.Permafrost covers over 16 per cent of the Earth’s total land surface63 and the landscape is highly variable, making it difficult to predict how the water of the thawing soils will respond. There is, therefore, a high degree of uncertainty over the actual and relative amounts of CO2 and methane that will be released from the permafrost, and the feedback effect that this may have.

55.The projections of future temperature and climate change made by the IPCC to date do not take account of the effects of melting permafrost and the potential climate feedback that may result. This has resulted in some criticism of the projections, and the emissions targets that are derived from them.64 The United Nations Environmental Programme (UNEP) has previously recommended that the IPCC should produce a special report on the effects of permafrost carbon feedback.65

56.A related issue concerns the release of methane from the Arctic seabed. As oceanic temperatures increase, there is a concern that methane trapped within the Arctic seabed will be released into the atmosphere, causing still further warming. The Arctic Methane Emergency Group stated that observations showed that this was already happening.66 Prof Wadhams told us:

“This is a much more serious and immediate problem than methane emissions from tundra, and it is going to build up to be an extremely serious problem … over the next few decades. The immediate fear is the emission of methane from shallow offshore waters off the east Siberian shelf in the Arctic in the summer … This is an unprecedented situation: the retreat of sea ice in the summer leading to warmer offshore waters over the shallow shelves of the Arctic, which is leading to offshore permafrost thawing, which is leading to a methane hydrate release as methane … It is probably the most important problem that we are facing in the Arctic, and we need to study it most strongly”.67

57.The Natural Environment Research Council (NERC) Arctic Office told us however that there is “no clear evidence of significant methane emissions reaching the atmosphere. The vast majority of methane appears to be oxidised within the water column”.68 The Met Office identified methane emissions from terrestrial and marine sources as an “important data gap”.69 The British Antarctic Survey (BAS) also acknowledged that research and knowledge in this field was lacking:

“The quantification of methane in near-surface terrestrial permafrost and marine sediments is only poorly assessed. The hypothesis that warming of the atmosphere, permafrost and/or coastal seas could release considerable quantities of this potent greenhouse gas, which would constitute a strong positive feedback amplifying climate change, will not be tested until more data on the distribution and release of methane has been acquired”.70

58.The potential for significant amounts of carbon dioxide and methane to be released from the Arctic permafrost and seabed, as a result of rising temperatures, is acknowledged but not yet fully measured or understood. Further research is required if the risks associated with these issues are to be fully calculated and planned for, both in the Arctic and beyond. We recommend that NERC should ensure that this issue is considered in any new dedicated Arctic research programme.

Further Arctic impacts of a changing climate

Ocean temperatures and ocean acidification

59.As mentioned in paragraph 43, the colder waters of the Arctic are able to absorb more CO2 than warmer regions. Uptake of CO2, however, also makes water more acidic (lower pH values). Arctic waters are currently experiencing widespread and rapid ocean acidification, which has the potential to affect many ecosystems and biological processes negatively, including shell formation and calcification of coral and marine plankton species. We were told that the Arctic Ocean had experienced long term declines in seawater pH and that these changes could have implications for marine ecosystems.71 A recent report by the Arctic Council concerning ocean acidification concluded that:

“The Arctic Ocean is rapidly accumulating carbon dioxide leading to increased ocean acidification—a long-term decline in seawater pH. This ongoing change impacts Arctic marine ecosystems that are already affected by rising temperatures and melting sea ice.

Arctic Ocean acidification has the potential to affect both commercial fisheries that are important to northern economies, and marine resources that are used by Arctic indigenous people”.72

60.Concerns were also expressed regarding longer term reductions in the capacity of the Arctic Ocean to absorb CO2. The Arctic Ocean is a region of deep-water formation, meaning that any CO2 absorbed in high latitude waters is transported down to depth and removed from contact with the atmosphere, potentially for thousands of years.73 We were told that influxes of freshwater from melting land ice mean that a continued freshening of the Arctic Ocean is likely to be observed, and that such freshening would reduce the density of the water in the Arctic. A reduction in density would slow the rate of deep-water formation.74 A warming climate may, therefore, decrease the deep-water formation of the Arctic Ocean, with negative implications for CO2 absorption and carbon storage in the ocean.75

61.The general paucity of knowledge regarding the sinking of carbon in the Arctic, and its wider implications, was also consistently emphasised in the evidence that we received.76 It is clear that further research is required to understand these important issues.

Arctic Ocean turbulence

62.The water column within the Arctic Ocean is highly stratified, with layers of water from different sources and with different levels of salinity, density and temperature overlying each other. Because currents in the Arctic are relatively slow, with water circulating at approximately 1–2cm per second, this stratification tends to be relatively stable.

63.A reduction in sea ice coverage exposes the ocean to direct forcing by the wind, allowing the wind to transmit momentum directly to the ocean circulation. We were told that this could potentially increase turbulence within the ocean, causing different layers of water to mix and causing heat stored in deeper waters to reach the ocean surface.77

64.This would have the potential to act as another feedback mechanism, with increased surface water temperature leading to increased further loss of sea ice. Dr Sheldon Bacon of the National Oceanography Centre, who observed that ocean ‘spin-up’ had already been witnessed in the Arctic Ocean north of Alaska, outlined the potential implications:

“If you enable a mechanism to mix heat up from below towards the surface, the confidently predicted seasonal decline of sea ice could very rapidly transform into a continuous absence through accessing the large subsurface reservoir of heat”.78

Impacts beyond the Arctic

Potential effects upon the ocean circulation

65.Although representing only three per cent of the global ocean area, the Arctic Ocean receives ten per cent of the global total river flows.79 Freshwater influx from major rivers that flow into the Arctic Ocean and from melting land ice has increased markedly over the past two decades.80 We were told that an “enormous volume” of freshwater has now accumulated in the Beaufort Sea, with anticyclonic wind patterns and ocean currents acting to concentrate freshwater in this location.81 Should these environmental restraints weaken or disappear, there is the potential for substantial volumes of freshwater to be released from the Arctic Ocean into other oceans.

66.We were told that such a release could have potential implications for the large scale ocean circulation which currently draws warm Atlantic waters northwards towards the Arctic Ocean82, where they sink below colder Arctic waters. This movement of water influences the distribution of heat around the planet; as warm waters, for instance, pass by the UK, westerly winds extract heat from the ocean. The ocean cools, the atmosphere warms, and this contributes to the UK experiencing a relatively benign climate as compared to nations at comparable latitudes.

67.We were told that models were limited in their capacity to predict changes to the circulation; Dr Richard Wood of the Met Office suggested that “The idea of a rapid collapse or shutdown is something that has happened in the past, but the consensus is that it is very unlikely over the 21st century”. He went on to suggest that “a few” model simulations suggested that a collapse was possible in the 22nd century.83

68.Disturbance to, or a slowdown of, this ocean circulation therefore has the potential to cause an overall cooling of the climate of the UK. The British Antarctic Survey (BAS) told us that this was an area of active and urgent research.84

Potential changes to the jet stream

69.The jet stream is the term commonly used to describe high altitude winds which affect weather patterns in the northern hemisphere; it is fuelled, in part, by differentials in temperature between mid and high latitudes. As Arctic temperatures rise, and the temperature differential between mid-latitudes and the Arctic accordingly reduces, there is the potential for the jet stream to slow down.85

70.As the jet stream slows, there is the potential for it to meander, and to drift further southwards, causing changes in the distribution of temperature and precipitation patterns. This could have significant impacts for the weather of the UK; we were told that likely consequences could include heat waves in the summer and increased snow and heavy rain in winter.86 There is also the potential for extreme weather to persist in one place for longer than would usually be the case87; changes to the jet stream have been identified as causative factors in the 2013–14 ‘Arctic blast’ in Canada and the northern US.88 Dr Nalân Koç of the Norwegian Polar Institute told us that:

“We can surely say that the Arctic is influencing climate patterns well beyond the boundaries of the Arctic itself. It is having an impact on the whole northern hemisphere”.89

Conclusions

71.The Arctic region is at the frontline of climate change and is being affected more rapidly by climate change than other parts of the globe. Particular concerns exist over melting land ice and a consequent rise in sea levels, as well as diminishing sea ice and melting permafrost. Loss of sea ice is expected to continue in the Arctic Ocean, with open water contributing to the further amplification of climate change. Physical, ecological, economic and geopolitical changesboth negative and positiveare arising as a result of the changing Arctic climate, and polar warming will have an impact upon ecosystem dynamics and human communities. While reductions in sea ice extent will make access to parts of the marine Arctic easier in future, changes such as permafrost and ice road melting may make investment in the terrestrial Arctic more difficult at least in the medium term, although there may be countervailing factors: the jury is out.

72.Understanding of the effects of climate change upon the Arctic and their causes in many places is lacking or severely limited. A great deal of further research is still required in order to assess and understand the effects and implications of Arctic climate change.

73.The impacts of Arctic changes are considered in the remaining chapters of this report. The consequences of climate change in the Arctic will bring opportunities, costs and risks, all of which will need addressing and managing.

6 AMAP, Snow, Water, Ice and Permafrost in the Arctic (SWIPA): Climate Change and the Cryosphere (2011): http://www.amap.no/documents/download/1448 [accessed 19 February 2015]

7 IPCC, Fifth Assessment Report, 2014

8 IPCC, First Assessment Report, 1990

9 Written evidence from Prof Terry Callaghan (ARC0030), WWF-UK (ARC0050), Dr Ed Hawkins, Dr Sheldon Bacon and Prof Chris Rapley (ARC0013), the Geological Society (ARC0031), and the National Centre for Atmospheric Science (ARC0021). We were told that these measurements were usually based on land temperature data; measurements of temperature over the Arctic Ocean were more limited.

10 Q 18 (Dr Ed Hawkins)

11 AMAP, Snow, Water, Ice and Permafrost in the Arctic (SWIPA): Climate Change and the Cryosphere (2011): http://www.amap.no/documents/download/1448 [accessed 19 February 2015]. See also: AMAP, Arctic Climate Issues 2011: Changes in Arctic Snow, Water, Ice and Permafrost (2012): http://www.amap.no/documents/doc/arctic-climate-issues-2011-changes-in-arctic-snow-water-ice-and-permafrost/129 [accessed 19 February 2015]

12 Written evidence from Prof Terry Callaghan (ARC0030)

13 Q 17 (Dr Ed Hawkins)

14 Q 85 (Dr Jan-Gunnar Winther). See also written evidence from Prof Andy Shepherd (ARC0045)

15 QQ 17–19 (Prof Chris Rapley, Dr Ed Hawkins)

16 Q 93 (Dr Nalân Koç)

17 Q 174 (Ben Ayliffe)

18 Written evidence from WWF-UK (ARC0050), and Dr Ed Hawkins, Dr Sheldon Bacon and Prof Chris Rapley (ARC0013). The loss is relative to the 1981–2010 average. The maximum extent of winter ice has decreased by around three to four per cent per decade over the same period.

19 Written evidence from WWF-UK (ARC0050)

20 Written evidence from Dr Ed Hawkins, Dr Sheldon Bacon and Prof Chris Rapley (ARC0013)

21 See Chapter 3.

22 IPCC, Fourth Assessment Report, 2007

23 These matters are discussed further in Chapter 5.

24 Written evidence from Lloyd’s Register (ARC0048)

25 Q 83 (Dr Nalân Koç), written evidence from the Natural Environment Research Council (NERC) Arctic Office (ARC0028)

26 Q 83 (Dr Nalân Koç)

27 Q 30 (Prof Peter Wadhams)

28 Q 30 (Prof Andy Shepherd)

29 Q 30 (Prof Peter Wadhams)

30 National Snow & Ice Data Center (NSIDC), ‘A summer storm in the Arctic’: http://nsidc.org/arcticseaicenews/2012/08/a-summer-storm-in-the-arctic/ [accessed 19 February 2015]

31 National Oceanic and Atmospheric Administration (NOAA), Arctic Report Card 2013: Sea Ice: http://www.arctic.noaa.gov/report13/sea_ice.html [accessed 19 February 2015]

32 As detailed previously, satellite records began in 1979.

33 34 (Prof Peter Wadhams). See also written evidence from the Geological Society (ARC0031).

34 Written evidence from Prof Daniel Feltham, Prof Andy Shepherd, Prof Chris Rapley and Dr Sheldon Bacon and Dr Ed Hawkins (ARC0049)

35 Ibid.

36 Q 31 and Q 34 (Prof Andy Shepherd), written evidence from Prof Andy Shepherd (ARC0045)

37 Written evidence from Prof Peter Wadhams (ARC0006)

38 Written evidence from Prof Andy Shepherd (ARC0045)

39 Written evidence from Profs Daniel Feltham, Andy Shepherd, Chris Rapley and Drs Sheldon Bacon and Ed Hawkins (ARC0049), and Dr Ed Hawkins, Dr Sheldon Bacon and Prof Chris Rapley (ARC0013)

40 Prof Jonathan Bamber et al, ‘A new bed elevation dataset for Greenland’, The Cryosphere, 7 (2), (2013) pp 499–510: http://www.the-cryosphere.net/7/499/2013/tc-7-499-2013.pdf [accessed 19 February 2015]

41 Q 33 (Prof Andy Shepherd)

42 Written evidence from the National Oceanography Centre (ARC0032)

43 Written evidence from the NERC Arctic Office (ARC0028). See also: Alfred Wegener Institute, ‘Large-scale assessment of the Arctic Ocean: significant increase in freshwater content since 1990s’ (24 March 2011): http://www.awi.de/en/news/press_releases/detail/item/large_scale_assessment_of_the_arctic_ocean_significant_increase_in_freshwater_content_since_1990s/?cHash=9ee44ce1b020d5b63e5ff3086d3ad689 [accessed 19 February 2015]

44 Written evidence from the NERC Arctic Office (ARC0028)

45 The cryosphere comprises those parts of the Earth’s surface covered by frozen, or partially frozen, water.

46 Around 98 per cent of this cover is in the northern hemisphere. See NSIDC State of the Cryosphere website: https://nsidc.org/cryosphere/sotc/snow_extent.html [accessed 19 February 2015, last updated 6 February 2014]

47 AMAP, Snow, Water, Ice and Permafrost in the Arctic (SWIPA): Climate Change and the Cryosphere (2011): http://www.amap.no/documents/doc/change-in-snow-cover-duration-for-autumn-snow-cover-onset-period-and-spring-snow-cover-melt-period-between-197273-and-200809/977 [accessed 19 February 2015]

48 Written evidence from Prof Terry Callaghan (ARC0030)

49 NOAA, Arctic Report Card 2014: Terrestrial Snow Cover: http://www.arctic.noaa.gov/reportcard/snow_cover.html [accessed on 19 February 2015]. See paragraph 27.

50 Parliamentary Office of Science and Technology (POST), Risks from Climate Feedbacks, PN 454 (January 2014): http://www.parliament.uk/business/publications/research/briefing-papers/POST-PN-454/risks-from-climate-feedbacks [accessed 19 February 2015]

51 Written evidence from the Arctic Methane Emergency Group (AMEG) (ARC0055)

52 See, for example, IPCC First Assessment Report, 1990.

53 Written evidence from Prof Terry Callaghan (ARC0030)

54 NOAA, Arctic Report Card: 2013 Update; Permafrost (2013): http://www.arctic.noaa.gov/report13/permafrost.html [accessed 19 February 2015]

55 Prof Terry Callaghan et al, ‘A new climate era in the sub-Arctic: Accelerating climate changes and multiple impacts’, Geophysical Research Letters, vol. 37, (2010)

56 NOAA, Arctic Report Card: 2013 Update; Permafrost (2013): http://www.arctic.noaa.gov/report13/permafrost.html [accessed 19 February 2015]

57 AMAP, Snow, Water, Ice and Permafrost in the Arctic (SWIPA): Climate Change and the Cryosphere (2011): http://www.amap.no/documents/download/1448 [accessed 19 February 2015]

58 Written evidence from the NERC Arctic Office (ARC0028)

59 Written evidence from Dr Ed Hawkins, Dr Sheldon Bacon and Prof Chris Rapley (ARC0013)

60 Parliamentary Office of Science and Technology, Risks from Climate Feedbacks, PN 454 (January 2014): http://www.parliament.uk/briefing-papers/POST-PN-454/risks-from-climate-feedbacks [accessed 19 February 2015]

61 Ibid.

62 Ibid.

63 Ibid.

64 Dr Kevin Schaefer et al, ‘The impact of the permafrost carbon feedback on global climate’, Environmental Research Letters, vol. 9, (2014)

65 UNEP, Policy implications of warming permafrost (2013): http://www.unep.org/pdf/permafrost.pdf [accessed on 20 February 2015]

66 Written evidence from AMEG (ARC0055)

67 35 (Prof Peter Wadhams)

68 Written evidence from the NERC Arctic Office (ARC0028)

69 Written evidence from the Met Office (ARC0044)

70 Written evidence from the British Antarctic Survey (BAS) (ARC0018)

71 Written evidence from Greenpeace UK (ARC0016)

72 AMAP, ‘Arctic Ocean Acidification Overview Report’ (May 2014): http://www.arctic-council.org/index.php/en/resources/news-and-press/news-archive/872-amap-releases-arctic-ocean-acidification-overview-report [accessed on 19 February 2015]

73 Written evidence from the National Oceanography Centre (ARC0032)

74 Ibid.

75 Written evidence from NERC (ARC0041) and National Oceanography Centre (ARC0032)

76 Written evidence from the NERC Arctic Office (ARC0028) and National Oceanography Centre (ARC0032)

77 Written evidence from the National Oceanography Centre (ARC0032)

78 Q 23 (Dr Sheldon Bacon)

79 Q 20 (Dr Sheldon Bacon)

80 Written evidence from the NERC Arctic Office (ARC0028)

81 Ibid.

82 Q 20 (Dr Sheldon Bacon)

83 Q 223 (Dr Richard Wood)

84 Written evidence from BAS (ARC0018)

85 See Pallab Ghosh, ‘Wavier jet stream ‘may drive weather shift’, BBC News, (15 February 2014): http://www.bbc.co.uk/news/science-environment-26023166 [accessed on 19 February 2015]

86 Written evidence from the National Oceanography Centre (ARC0032)

87 Written evidence from AMEG (ARC0055) and the NERC Arctic Office (ARC0028)

88 Q 83 (Dr Nalân Koç), Q 94 (Dr Jan-Gunnar Winther), written evidence from Arctic Methane Emergency Group (ARC0055)

89 Ibid.