Ice is melting and the sea level is rising
The ocean and cryosphere (the frozen parts of our planet) are critical for life on Earth. However, ice is melting at an unprecedented rate, sea levels are rising, and oceans are warming - with more to come.
Our world-leading research reveals that human-caused climate change is melting the world's ice sheets and glaciers, contributing to global sea-level rise.
We are also assessing the impacts on deep-sea and open-ocean ecosystems and the unprecedented pressures they're facing due to climate change.
- Human-caused climate change is causing widespread loss of glaciers and sea ice at ‘unprecedented’ rates.
- The Arctic will be 'practically sea ice-free' at least once before 2050.
- Melting glaciers and ice sheets due to warming are causing sea level rise.
- The global sea level has already risen by 20cm, with more to come.
- The frequency of marine heatwaves has nearly doubled since the 1980s.
- Human-caused climate change is causing ocean acidification to increase and oxygen levels to decrease.
- Even if we make drastic reductions, many impacts are irreversible for centuries to millennia. This means ice will keep melting and oceans rising, potentially inundating our coastal communities.
So, what is happening?
You can find out key information by clicking on each heading below:
What is the latest science on ice sheets, glaciers and sea-level rise?
Our researchers analyse ice-sheet and glacier melting from the world's polar and high-mountain regions and project their impact on sea-level rise. For example, we have shown that Greenland today is losing ice seven times faster than two decades ago.
This work supported the IPCC AR6 assessments and as the primary evidence base for global policymakers.
The IPCC reveals widespread loss of snow and ice in recent decades, with some in states unseen in centuries. Human influence is the leading cause of reductions in Arctic sea ice and the widespread retreat of glaciers.
In the last decade, the annual average Arctic sea ice area reached its lowest level since 1850. In addition, the late-summer Arctic sea ice area was smaller than at any time in at least the last thousand years.
The glacier retreat of almost all the world's glaciers since the 1950s is unprecedented in at least two thousand years.
Melting ice sheets and glaciers, along with the expansion of the ocean as it warms, have led to a global mean sea level increase of 0.2 metres between 1901 and 2018. The global mean sea level has risen faster since 1900 than over any preceding century in at least the last three thousand years. It has been identified that human influence is the main driver for sea level increases.
Notably, the speed that sea level is rising is accelerating:
- 1.3 millimetres per year during 1901-1971
- 1.9mm per year during 1971-2006
- 3.7mm per year during 2006-2018.
Many of the impacts of global warming are irreversible for centuries to millennia, especially changes in the ocean, ice sheets and global sea level.
The latest IPCC assessment is based on improved data and understanding of the factors that drive surface melt and surface mass balance changes. For example, the likelihood of human activity impacting the increased surface melt of the Greenland ice sheet has been upgraded from 'likely' to 'very likely'.
Here are a couple of notable differences:
Topic |
Fifth Assessment Report (AR5) 2013/14 |
Sixth Assessment Report (AR6) 2021 |
| Greenland ice sheet |
Anthropogenic influences likely contributed to…the increased surface mass loss of the Greenland ice sheet since 1993.
|
It is very likely that human influence has contributed to the observed surface melting of the Greenland Ice Sheet over the past two decades. |
| Arctic sea ice | There is medium confidence from reconstructions that over the past three decades, Arctic summer sea ice retreat was unprecedented and sea surface temperatures were anomalously high in at least the last 1,450 years. | In 2011–20, annual average Arctic sea ice area reached its lowest level since at least 1850 (high confidence). Late summer Arctic sea ice area was smaller than at any time in at least the past 1,000 years (medium confidence). |
| Arctic sea ice |
Anthropogenic influences have very likely contributed to Arctic sea ice loss since 1979. |
Human influence is very likely the main driver of…the decrease in Arctic sea ice area between 1979–88 and 2010–19 (about 40% in September and about 10% in March). |
| Glaciers | The average rate of ice loss from glaciers around the world, excluding glaciers on the periphery of the ice sheets, was very likely 226 [91 to 361] Gt/yr over the period 1971 to 2009, and very likely 275 [140 to 410] Gt/yr over the period 1993 to 2009. | The global nature of glacier retreat, with almost all of the world’s glaciers retreating synchronously, since the 1950s is unprecedented in at least the last 2,000 years (medium confidence). |
| Glaciers | Anthropogenic influences likely contributed to the retreat of glaciers since the 1960s. | Human influence is very likely the main driver of the global retreat of glaciers since the 1990s. |
| Sea level rise | It is very likely that the mean rate of global averaged sea level rise was 1.7 [1.5 to 1.9] mm/yr between 1901 and 2010, 2.0 [1.7 to 2.3] mm/yr between 1971 and 2010, and 3.2 [2.8 to 3.6] mm/yr between 1993 and 2010. | Global mean sea level increased by 0.20 [0.15 to 0.25] metres between 1901 and 2018. The average rate of sea level rise was 1.3 [0.6 to 2.1] mm/yr between 1901 and 1971, increasing to 1.9 [0.8 to 2.9] mm/yr between 1971 and 2006, and further increasing to 3.7 [3.2 to 4.2] mm/yr between 2006 and 2018 (high confidence). |
| Sea level rise | It is very likely that there is a substantial anthropogenic contribution to the global mean sea level rise since the 1970s. | Human influence was very likely the main driver of these [observed sea level increases] since at least 1971. |
| Sea level rise | Since the early 1970s, glacier mass loss and ocean thermal expansion from warming together explain about 75% of the observed global mean sea level rise (high confidence). | Heating of the climate system has caused global mean sea level rise through ice loss on land and thermal expansion from ocean warming. Thermal expansion explained 50% of sea level rise during 1971–2018, while ice loss from glaciers contributed 22%, ice sheets 20% and changes in land water storage 8%. |
What is the latest science on the world's oceans?
Our research assessed the climate impacts on deep-sea and open-ocean ecosystems, which supported the IPCC AR6 assessments.
The IPCC report reveals that the global ocean has warmed faster over the past century than since the end of the last deglacial transition (around 11,000 years ago).
Marine heatwaves have also become more frequent in the 20th century, nearly doubling since the 1980s.
Ocean acidification is caused by the uptake of CO₂. Acidification has occurred across all of the oceans and is reaching depths beyond 2,000m in the Southern Ocean and North Atlantic. Human-caused emissions are the main driver of current global acidification of the surface open ocean, which has increased since the 1950s.
Oxygen levels have dropped in many ocean regions since the mid-20th century, and the geographic range of many marine organisms has changed over the last twenty years.
Many of the impacts, particularly changes in the ocean, ice sheets and global sea level, are irreversible for centuries to millennia.
The latest IPCC assessment is based on improved data and understanding. It clearly links human influence to changes to the ocean, including warming, more frequent marine heatwaves, ocean acidification, and reduced oxygen levels.
Here are a couple of notable differences:
Fifth Assessment Report (AR5) 2013/14 |
Sixth Assessment Report (AR6) 2021 |
|
| Ocean warming |
It is virtually certain that the upper ocean (0−700 metres) warmed from 1971 to 2010, and it likely warmed between the 1870s and 1971. |
It is virtually certain that the global upper ocean (0–700 metres) has warmed since the 1970s. |
| Ocean warming | It is very likely that anthropogenic forcings have made a substantial contribution to increases in global upper ocean heat content (0–700 metres) observed since the 1970s. There is evidence for human influence in some individual ocean basins. | It is…extremely likely that human influence is the main driver [of ocean warming]. |
| Ocean acidification | Ocean acidification is quantified by decreases in pH. The pH of ocean surface water has decreased by 0.1 since the beginning of the industrial era (high confidence), corresponding to a 26% increase in hydrogen ion concentration. | A long-term increase in surface open ocean pH occurred over the past 50m years (high confidence), and surface open ocean pH as low as recent decades is unusual in the last 2m years (medium confidence). |
| Ocean salinity | Anthropogenic influences have contributed to…changes in surface and sub-surface ocean salinity (very likely). | It is…extremely likely that human influence contributed to the pattern of observed changes in near-surface ocean salinity. |
AR6 used a combination of historical observations, climate models and an update of climate sensitivity to provide the best estimate that the world might pass the 1.5C and 2C global warming levels. The report sets out five different pathways emissions could take for the coming decades, with 'climate future' scenarios attached to them.
Even if the world manages to limit warming to 1.5C, some long-term warming impacts are already inevitable and irreversible. These include sea level rises, the melting of Arctic ice, and the warming and acidification of the oceans.
Future predictions for ice sheets, glaciers and sea-level rise
Significant contributions by our researchers enabled the latest AR6 report, for the first time, to include accurate predictions on the impact of melting ice around the margins of Antarctica and Greenland and high-mountain regions such as the Himalayas, Iceland, and South America.
The latest IPCC report reveals more certainty around aspects of observed change, including projections for the future. For example, the previous projection for an 'ice-free' Arctic in September during the 21st century was initially made under a high emissions scenario. Now, the Arctic is likely to be 'practically sea ice free' at least once before 2050 under all five scenarios considered in the report.
The results of AR6 are clear
The difference between 1.5 and 2 degrees is substantial. Every increment in warming will amplify the melting of glaciers and ice sheets and the loss of summer Arctic sea ice.
Many changes due to past and future greenhouse gas emissions are irreversible for centuries to millennia. This particularly affects the world's oceans and ice, meaning ice will keep melting and oceans rising towards our many crowded coastal cities.
- Glaciers will continue to lose mass for at least several decades even if global temperature is stabilised.
- The Arctic is now likely to be 'practically sea ice free' at least once before 2050. Future Arctic warming will be "above two times the rate of global warming".
- Mass loss over the 21st century is virtually certain for the Greenland Ice Sheet and likely for the Antarctic Ice Sheet.
- Coastal areas will see continued sea-level rise throughout the 21st century. It is likely to rise between 28cm and 100cm by the end of the century. However, it could also be as high as 2300cm.
- Rising sea levels will contribute to more frequent and severe coastal flooding in low-lying areas and coastal erosion.
- Extreme sea-level events that previously occurred once in 100 years could happen every year by the end of this century.
Here are a couple of notable differences:
Topic |
Fifth Assessment Report (AR5) 2013/14 |
Sixth Assessment Report (AR6) 2021 |
| Greenland ice sheet |
The increase in surface melting of the Greenland ice sheet will exceed the increase in snowfall, leading to a positive contribution [to sea level rise] from changes in surface mass balance to future sea level (high confidence). |
Continued ice loss over the 21st century is virtually certain for the Greenland Ice Sheet…There is high confidence that total ice loss from the Greenland Ice Sheet will increase with cumulative emissions. |
| Arctic sea ice | A nearly ice-free Arctic Ocean in September before mid-century is likely for scenario RCP8.5 (medium confidence). A projection of when the Arctic might become nearly ice-free in September in the 21st century cannot be made with confidence for the other scenarios. | The Arctic is likely to be practically sea ice-free in September at least once before 2050 under the five illustrative scenarios considered in this report, with more frequent occurrences for higher warming levels. |
| Glaciers | By the end of the 21st century, the global glacier volume, excluding glaciers on the periphery of Antarctica, is projected to decrease between 15 to 55% and 35 to 85% (medium confidence). | Mountain and polar glaciers are committed to continue melting for decades or centuries (very high confidence). |
| Antarctic ice sheet | While surface melting will remain small, an increase in snowfall on the Antarctic ice sheet is expected (medium confidence), resulting in a negative contribution to future sea level from changes in surface mass balance. | Continued ice loss over the 21st century is…likely for the Antarctic Ice Sheet. |
| Antarctic ice sheet | Abrupt and irreversible ice loss from a potential instability of marine-based sectors of the Antarctic ice sheet in response to climate forcing is possible, but current evidence and understanding is insufficient to make a quantitative assessment. | Abrupt responses and tipping points of the climate system, such as strongly increased Antarctic ice sheet melt and forest dieback, cannot be ruled out (high confidence). |
| Sea level rise | Global mean sea level rise for 2081–2100 relative to 1986–2005 will likely be in the ranges from 0.26 to 0.55 metres up to 0.45 to 0.82 metres (medium confidence). | It is virtually certain that global mean sea level will continue to rise over the 21st century. Relative to 1995-2014, the likely global mean sea level rise by 2100 is 0.28-0.55 metres under the very low greenhouse gas (GHG) emissions scenario, 0.32-0.62 metres under the low GHG emissions scenario, 0.44-0.76 metres under the intermediate GHG emissions scenario, and 0.63-1.01 metres under the very high GHG emissions scenario. |
| Sea level rise | It is virtually certain that global mean sea level rise will continue beyond 2100, with sea level rise due to thermal expansion to continue for many centuries. | In the longer term, sea level is committed to rise for centuries to millennia due to continuing deep ocean warming and ice sheet melt, and will remain elevated for thousands of years (high confidence). |
Future predictions for the world's oceans
The latest IPCC report reveals more certainty around aspects of observed change, including projections for the future. For example, the AR5 summary did not include projections on marine heatwaves. However, the latest report notes with high confidence that the frequency of marine heatwaves will continue to increase with additional global warming.
The results of AR6 are clear
The difference between 1.5 and 2 degrees is substantial: every increment of warming translates into increased risks.
- even under a low-warming scenario, the amount of ocean warming observed since 1971 will likely at least double by 2100
- under a high-warming scenario, the amount of ocean warming will increase by 4 - 8 times
- ocean acidification, deoxygenation and marine heatwaves will continue to increase in the 21st century.
- even if the world restricts warming to 1.5-2℃, consistent with the Paris Agreement, marine heatwaves will become four times more frequent by the end of the century.
Here are a couple of notable differences:
Fifth Assessment Report (AR5) 2013/14 |
Sixth Assessment Report (AR6) 2021 |
|
| Ocean warming |
The global ocean will continue to warm during the 21st century. Heat will penetrate from the surface to the deep ocean and affect ocean circulation. |
Past greenhouse gas (GHG) emissions since 1750 have committed the global ocean to future warming (high confidence). Over the rest of the 21st century, likely ocean warming ranges from 2–4 to 4–8 times the 1971–2018 change. |
| Ocean warming | [not included in AR5 summary] | With additional global warming, the frequency of marine heatwaves will continue to increase (high confidence) |
| Ocean acidification | Earth System Models project a global increase in ocean acidification for all scenarios. The corresponding decrease in surface ocean pH by the end of 21st century is in the range from 0.06 to 0.07 up to 0.30 to 0.32. | Based on multiple lines of evidence…ocean acidification (virtually certain)…will continue to increase in the 21st century, at rates dependent on future emissions. |
Ice sheets and glaciers
Our ice-sheet and glacier scientists have spearheaded new methods to collect invaluable satellite and field data and developed new computer modelling techniques to monitor and predict changes in the Earth's ice-covered regions.
For example, we demonstrated that Greenland today is losing ice seven times faster than two decades ago.
We developed new computer modelling techniques that determined oceans' impact on the flow and retreat of ice around West Antarctica and Greenland. As a result, our equations have greatly improved predictions of the Antarctic Ice Sheet's fate and its contribution to global sea-level rise over the next 200 years.
In addition, our researchers have developed new data analytic methods from satellite observations, providing greater insight into terrains. We can also better pinpoint where the ocean is eroding ice under the melting Antarctic ice shelves.
Significant contributions by our researchers enabled the latest AR6 report, for the first time, to include accurate predictions on the impact of melting ice around the margins of Antarctica and Greenland and high-mountain regions such as the Himalayas, Iceland, and South America.
The world's oceans
Our research on marine ecosystems, particularly seamounts, coldwater corals and sponges, is used to assess climate impacts on open ocean and deep seafloor ecosystem structure and functioning. We also help inform the levels of risk under future conditions of global warming and the unprecedented pressures they're facing due to climate change.
Latest research
For the IPCC Sixth Assessment, we made significant contributions in analysing the impacts of climate change on the world's ice sheets, glaciers, oceans and the global sea level.
Various works from our researchers were cited throughout, plus several figures were used by the AR6 report.
Our work with the IPCC
Find out more
The following pages on this website may interest you:
|
Harnessing satellites We are conducting world-leading research with organisations such as the European Space Agency. Our satellite observations of ice-sheet and glacier melting have reduced uncertainties in estimating future global sea-level rise. |
|
|
Numerical modelling Numerical-modelling equations and strategies developed by our researchers have contributed to greatly reduced uncertainties in the British Antarctic Survey (BAS) programme for numerically modelling the future of the ice sheets. |
University impact
You can also read related stories on the University Impact website:
|
Signals from a drowning world Melting ice sheets and glaciers are a startling reminder of the rate of climate change. However, measuring ice loss was an inaccurate science... until Edinburgh experts helped change things. |
|
|
Uncovering the mysteries of the deep The health of the world’s oceans might be high on the political agenda, but how do we maintain their wellbeing with so much still unknown about them? Edinburgh researchers have been instrumental in a major project that has shone a light into the depths of the Atlantic. |
The leaps we’ve made during the past decade have contributed to a much higher degree of public and political understanding about the possible futures we could have if we do nothing. If there were ever a moment to act, it is now.”
We have a tremendous amount of geological evidence on how the ice sheet has grown and reduced in size during the past two million years, and for the past 50 years, we’ve been able to observe these changes from satellites. But what we’ve lacked until the past decade is the necessary level of precision to fully understand how our ice sheets and glaciers are changing or make useful predictions about how these changes will affect sea levels.
Want to know more?
We've provided some useful links for you. To see the information, simply click on each heading below:
Study with us, and join one of the largest and most successful groupings of geographers and geoscientists in the UK as we address the most compelling issues of our time.
The following degrees may be of interest to you:
Undergraduate study
Postgraduate study
- Earth Observation and Geoinformation Management
- Geographical Information Science (GIS)
- Marine Systems and Policies
Postgraduate research
Check out more of our diverse undergraduate, postgraduate and research degrees and help us change the world.
We've provided more information on our work and the role of the IPCC:
You can find more information on how our work supports global initiatives to mitigate the effects of climate change and accelerate the transition to a low-carbon economy.
The following pages on this website may interest you:
|
Harnessing satellites We are conducting world-leading research with organisations such as the European Space Agency. Our satellite observations of ice-sheet and glacier melting have reduced uncertainties in estimating future global sea-level rise. |
Harnessing satellites |
|
Numerical modelling Numerical-modelling equations and strategies developed by our researchers have contributed to greatly reduced uncertainties in the British Antarctic Survey (BAS) programme for numerically modelling the future of the ice sheets. |
Numerical modelling |
University impact
You can also read related stories on the University Impact website:
|
Signals from a drowning world Melting ice sheets and glaciers are a startling reminder of the rate of climate change. However, measuring ice loss was an inaccurate science... until Edinburgh experts helped change things. |
Signals from a drowning world |
|
Uncovering the mysteries of the deep The health of the world’s oceans might be high on the political agenda, but how do we maintain their wellbeing with so much still unknown about them? Edinburgh researchers have been instrumental in a major project that has shone a light into the depths of the Atlantic. |
Uncovering the mysteries of the deep |
-
Duration: 6 minutes 12 seconds
- Contributor: Dr Sian Henley
Light is flooding into the Arctic. There will be winners and losers.... That's what brought an international group of scientists to the Barents Sea to investigate how plant and animal life will adapt to the new normal.
This video is part one of a three-part series on the changing Arctic by Vox Media. Dr Sian Henley was one of the experts interviewed during the research expedition.
-
Duration: 39 minutes
- Contributor: Dr Claudia Colesie
- This video is in Spanish, with English subtitles
This video displays the fascinating world of polar environments. Watch Dr Claudia Colesie and fellow researchers as they travel to Antarctica for the 'Cryptocover' project. The project investigated biocomplexity and functioning of the cryptogamic cover in arid and polar regions. It was funded by the Spanish Research Council and the Spanish Antarctic research committee and coordinated by Professor Leopoldo Sancho, Complutense University of Madrid, Spain.
-
Duration: 4 minutes 16 seconds
- Contributors: Professor Murray Roberts and team
A landmark project to study the Atlantic Ocean’s vast depths has laid the foundations for efforts to safeguard the ocean for future generations. The most in-depth assessment of deep-sea ecosystems to date has led to the discovery of new species, offered greater insights into biodiversity and improved understanding of the damaging impacts of climate change. It also provided governments and industry with tools to help ensure the ocean’s resources are used more sustainably.
The ATLAS project involved more than 80 researchers from 13 different countries. Professor Murray Roberts was the project coordinator, with Dr Lea-Anne Henry, Dr Sebastian Hennige, Dr Johanne Vad, Dr Laurence De Clippele, and Dr Georgios Kazanidis also involved in the project.
You can watch a video that provides highlights about the project.