Effects
- Planetary Boundaries & Tipping Points
- Extreme weather & event attribution
- ENSO: El Niño & La Niña
- Feedback effects of warming
- Wildfires increasing
- Antarctica melting
- Antarctic sea ice disappearing
- Arctic sea ice disappearing
- Greenland melting
- Ocean currents changing
- Oceans warming
- Ocean acidification
- Melting permafrost & burning ice
- New Zealand’s disappearing glaciers
- Black carbon & ash on snow
- Seasons changing
- How we know about past climates: proxy data
Summary
[The] complete loss of Arctic sea ice in summer is now inevitable, even with the very lowest emissions pathways that peak temperatures at 1.6°C. This finding is a terminal diagnosis for that ecosystem and its essential role reflecting sunlight as the “Earth’s refrigerator,” something sea ice scientists have been warning for decades would come with continued high emissions. No one seems to have listened. – State of the Cryosphere Report 2022
Sea ice loss in the Arctic has triggered a critical tipping point that’s destroying the food chain – Live Science June 2026
- The Arctic Ocean is semi-enclosed, surrounded almost entirely by land—Eurasia, North America, Greenland and some smaller islands. The land keeps most of the sea ice penned up, making it less mobile than sea ice that forms around Antarctica.
- Sea ice is not the same as icebergs, which come from glaciers.
- Sea ice grows throughout the autumn and winter and then melts throughout the spring and summer; it has declined 95% in the past 33 years.
- The world’s oceans have absorbed around 93% of global warming to date with the Arctic warming 4 times faster than the global average (over the Barents Sea as much as 7 times faster) in part because the positive albedo effect of ice is rapidly diminishing, triggering feedback effects. This is known as ‘Polar Amplification’.
The planetary cooling effect of sea ice has reduced by 14% since the 1980s – Duspayev et al, 2024
- Recent research indicates the Arctic is now undergoing abrupt climate change, and that climate models underestimated this in part due to a giant and growing ‘blob’ of warm water (see the MOSAiC Expedition).
Effects
- Planetary Boundaries & Tipping Points
- Extreme weather & event attribution
- ENSO: El Niño & La Niña
- Feedback effects of warming
- Wildfires increasing
- Antarctica melting
- Antarctic sea ice disappearing
- Arctic sea ice disappearing
- Greenland melting
- Ocean currents changing
- Oceans warming
- Ocean acidification
- Melting permafrost & burning ice
- New Zealand’s disappearing glaciers
- Black carbon & ash on snow
- Seasons changing
- How we know about past climates: proxy data
Summary
[The] complete loss of Arctic sea ice in summer is now inevitable, even with the very lowest emissions pathways that peak temperatures at 1.6°C. This finding is a terminal diagnosis for that ecosystem and its essential role reflecting sunlight as the “Earth’s refrigerator,” something sea ice scientists have been warning for decades would come with continued high emissions. No one seems to have listened. – State of the Cryosphere Report 2022
Sea ice loss in the Arctic has triggered a critical tipping point that’s destroying the food chain – Live Science June 2026
- The Arctic Ocean is semi-enclosed, surrounded almost entirely by land—Eurasia, North America, Greenland and some smaller islands. The land keeps most of the sea ice penned up, making it less mobile than sea ice that forms around Antarctica.
- Sea ice is not the same as icebergs, which come from glaciers.
- Sea ice grows throughout the autumn and winter and then melts throughout the spring and summer; it has declined 95% in the past 33 years.
- The world’s oceans have absorbed around 93% of global warming to date with the Arctic warming 4 times faster than the global average (over the Barents Sea as much as 7 times faster) in part because the positive albedo effect of ice is rapidly diminishing, triggering feedback effects. This is known as ‘Polar Amplification’.
- Recent research indicates the Arctic is now undergoing abrupt climate change, and that climate models underestimated this in part due to a giant and growing ‘blob’ of warm water (see the MOSAiC Expedition).
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Some incoming radiation from the sun is reflected back into space due to the albedo effect of the cryosphere (ice caps, permafrost, glaciers) and atmospheric aerosols much of which, paradoxically, come from burning fossil fuels. About 89% of the retained excess heat is being absorbed by the oceans. The land takes up ~6%, the cryosphere absorbs ~4%—which is why it’s rapidly melting—and the remaining 1% is in the atmosphere.
- Icebergs: are made of that has broken off a glacier or ice shelf and floats out to sea or into lakes.
- Sea ice: forms when ocean water freezes over autumn and winter. Although sea ice is made from salty seawater, there isn’t much room for salt molecules to be trapped in the close-knit structure of ice, so the salt molecules are rejected into a dense, briny solution that drops into deeper water. This plays a crucial role in driving the world’s two largest ocean currents.
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A reduction in the formation of sea ice doesn’t raise sea levels, however it does trigger cascading feedback effects including but not limited to:
- Changing the world’s two largest ocean currents, with global implications.
- Melting permafrost and methane clathrates, which are releasing large volumes of the greenhouse gases carbon dioxide and methane into the atmosphere
- Changing global weather patterns: temperature differences between the poles and tropics is a key part of how global weather works. As the poles are warming 2-4 times faster than elsewhere, the temperature difference is declining. The polar jetstreams are now ‘wobbling’; instead of super-cold Arctic and hot tropical air kept in place at the poles and equator, they’re moving into temperate areas, causing weather extremes globally in 2022 and again in 2023.
- Phenological changes in phytoplankton, which is the base of the food chain, and loss of habitat for iconic species such as polar bears and godwits (which migrate to New Zealand) are now underway.
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Line graph time series of 2026 daily Arctic sea ice extent compared to decadal averages from the 1980s to the 2010s. The decadal averages are shown with different colored lines with purple for the 1980s, blue for the 1990s, green for the 2000s, and white for the 2010s. Thin white lines are also shown for each year from 2000 to 2024. 2026 is shown with a thick gold line, which is currently a record low for the current date. There is a long-term decreasing trend in ice extent for every day of the year shown on this graph between October and January by looking at the decadal average line positions.(Image: Zack Labe)
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Image: Dr. Zack Labe
State of the Cryosphere Report 2025
Summary: Arctic Sea Ice
Polar sea ice is essential for maintaining a livable global climate, with global risks from its decline ranging from disruption of weather and ocean currents; to accelerated Greenland and Antarctic melt and associated sea-level rise; to extinction of ice-dependent species at the base of the food chain for humans and many polar and marine mammals. Sea ice coverage at both poles has declined by 40–60% since satellite measurements began in 1979, with nearly all Antarctic sea ice decline occurring precipitously since 2016. While most attention is given to the September sea ice minimum in the Arctic, this loss has occurred year-round, in all months of the year including sea ice maximums, when the ice reaches its largest extent. A record-low maximum occurred in the Arctic in March 2025, and Antarctica’s record-low maximum was set in September 2023. Global sea-ice coverage, combining both poles, reached a record all-time low in February 2025.
Sea ice has declined not only in extent, but in thickness. Much of the Arctic Ocean used to be covered in thick, multi-year ice that was 4–7 years old. Such “old” ice has virtually disappeared, with even two or three-year-old ice comprising under 10% of today’s sea-ice coverage. Antarctic sea ice plays an essential role in several ways, including formation of Antarctic Bottom Water: the densest water mass on the planet, driving the entire global ocean “conveyor belt.” A 40% decline in sea ice in the Weddell Sea has reduced the production of Antarctic Bottom Water in this region by almost a third.
Future sea ice survival is extremely sensitive to current and future human emissions of greenhouse gases. If governments course-correct to 2025 NDCs consistent with 1.5°C of warming or below at 2100, sea ice may slowly begin to recover in the 2070s and beyond. At least one ice-free Arctic summer event seems increasingly likely however before 2050, and the summer ice-free period would increase with additional warming. NDCs that result in global mean temperatures of 2°C or above would lead to ice-free conditions in the Arctic every summer, with high-risk and unpredictable global impacts. Loss of Antarctic sea ice and associated ice shelves is less certain, but holds even greater long-term and non-reversible risks because the sea ice and ice shelves are essential to protecting Antarctica’s ice sheet, and holding sea-level rise to adaptable levels in coming decades and centuries.
More information
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Arctic or Polar Amplification are terms used to describe why the poles are warming far faster than the rest of the planet. There are several reasons for this:- The Albedo Effect: Click the next ‘Explainer’ tab for details.
- Ozone-depleting substances (this is a new area of research: see here for how this is happening).
- Air pressure differences between the tropics and the poles may also be a factor: warmer (and therefore denser, higher pressure) air tends to travel from the tropics to the cooler (lower pressure less dense air) poles (see 5-min. Video 1 here). However, weather systems are stalling as the jet stream wobbles; see the ‘Explainer’ tab below. While this allows cold arctic air to move further south for longer periods, it also allows warmer tropical air to invade polar latitudes. A very small rise in temperatures for long periods is leading to dramatic melting across Greenland, Antarctica, and Arctic sea ice.
- Climate system feedbacks have also changed ocean currents as well as the weather associated with them.
Arctic amplification intensification: ESA
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Clean ice and snow have a very high albedo, that is, they reflect up to 90% of solar radiation back into space The ocean is much darker, so it has a very low albedo, reflecting only about 6% of the incoming solar radiation and absorbing the other 94%, warming it much faster than the snow and ice (Fig. 4).As more ice forms, the water is cooler, leading to more ice forming, and so on, in a feedback effect. However,
Recent global temperature surge intensified by record-low planetary albedo – Science, 05 Dec. 2024 (Figs. 5 & 6)
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Image: Nathan Kurtz / NASA
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Image: Duspayev et al; Earth’s Sea Ice Radiative Effect from 1980 to 2023
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Image: Eliot Jaboson; data: NASA
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When the albedo effect creates dark water that absorbs more heat, that heat must go somewhere:
These warming surface waters are likely migrating down into the blob, which robotic temperature probes, moorings, and oceanographic surveys show is steadily warming and growing. With enough heat to melt the Arctic’s ice three to four times over, the blob could devour the ice from below if the barrier of the cold surface layers ever dissipates… Measurements from the eastern Arctic Ocean show the blob, usually found 150 meters below or deeper, has recently moved up to within 80 meters of the surface… The process, called “Atlantification [see the 2025 Arctic Report Card video below]” is already well underway in the Barents Sea, north of Norway, where fingers of warm Atlantic water have spread north and risen, melting sea ice even in winter months. The invasion shows no sign of stopping…”– Voosen, August 2020.
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In the Northern Hemisphere, the world’s second largest current, the Atlantic Meridional Overturning Current (AMOC) abruptly shut down when Earth warmed quickly at the end of the Last Glacial Maximum 14,500 years ago, leading to equally abrupt cooling over much of Europe (called the Younger Dryas), and an unstable climate that brought wild weather globally for several thousand years.
In the Southern Hemisphere, the Antarctic Circumpolar Current, the largest current, is also shutting down, allowing warm water eddies to reach further into Antarctica, with implications for sea level rise and changes to our weather patterns. Find out more about these currents and the links to research papers here (links to a page on this website).
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Earth viewed on a Spilhaus projection showing how oceanic currents circle the globe. Warm current are red, cool are blue.
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Polar regions are warming more than twice as fast as the rest of the planet, and this is changing our weather, which is strongly influenced by jetstreams including the polar vortex. Extreme hot or cold weather is often ‘stuck’ over one place for long periods.
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How plants and animals change the way they behave according to temperature (Video 3). See more about ‘phenology’ on this website.
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- 2026: Santos-Garcia, Sea ice loss drives a regime shift in Arctic Ocean nitrogen biogeochemistry, Nature Communications Earth & Environment 7| 442 (Open access)
- Plain English: Live Science
- 2025: Arctic Report Card; NOAA
- 2025: State of the Cryosphere Report, International Cryosphere Climate Initiative (ICCI), Stockholm, Sweden
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- 2025: Stroeve et al; Disappearing landscapes: The Arctic at +2.7°C global warming, Science 6 February
- Plain English: SciTech daily
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- 2024: NOAA Arctic Report Card 2024
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- 2023: Vermassen et al; A seasonally ice-free Arctic Ocean during the Last Interglacial, Nature Geoscience 16, pp723–729
- 2022: State of the Cryosphere
- 2022: NOAA Arctic Report Card
- 2022: Rantanen et al; The Arctic has warmed nearly four times faster than the globe since 1979, Nature Communications Earth and environment 3 |168
- Tandon, Carbon Brief explains the research (open access)
- 2021: NOAA Arctic Report Card
- 2021: Jacobs et al; The Arctic Is Now Warming Four Times As Fast As the Rest of the Globe, AGU Fall Meeting 13-17 December
- 2021: Bailey et al; Arctic sea-ice loss fuels extreme European snowfall, Nature Geoscience 14 pp283–288
- National Snow and Ice Data Centre (NSIDC)
- (undated) Harvey et al; Equator-to-pole temperature differences and the extra-tropicalstorm track responses of the CMIP5 climate models, NCAS-Climate, Department of Meteorology, University of Reading, UK
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- 2020: Timmermans et al; Warming of the interior Arctic Ocean linked to sea ice losses at the basin margins, Science Advances 4/8
- 2020: Voosen; Growing underwater heat blob speeds demise of Arctic sea ice, Science 25 August.
- 2020: Skagseth et al; Reduced efficiency of the Barents Sea cooling machine, Nature Climate Change 10, pp661-666
- 2020: Jansen et al; Past perspectives on the present era of abrupt Arctic climate change Nature Climate Change 10, pp714–721
- 2020: Ouyang et al; Sea-ice loss amplifies summertime decadal CO2 increase in the western Arctic Ocean Nature Climate Change 10, 678–684
- 2020: NASA Earth Observatory: Ice Bridge
- 2020: NASA; Mapping Snow on Arctic Ice
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- 2019: NASA: 2019 Arctic Sea Ice Minimum Tied for Second Lowest On Record
- 2019: NOAA Richter-Menge et al; Arctic Report Card 2019
- 2019: National Geographic: The Arctic Is Heating Up September 2019 special issue
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- 2019: Cheng et al; How fast are the oceans warming? Science 363/6423 pp128-129
- 2018 NOAA Arctic Report Card: Executive summary
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- 2026: Santos-Garcia, Sea ice loss drives a regime shift in Arctic Ocean nitrogen biogeochemistry, Nature Communications Earth & Environment 7| 442 (Open access)