State of the Cryosphere Report 2024
Summary: Arctic Sea Ice
Current NDCs (2.3°C by 2100): Global feedbacks from sea ice loss at both poles would increase adaptation and loss-and-damage burdens around the planet. Every year, the Arctic Ocean would be practically sea ice-free for up to four months (July-October). The less reflective open water would absorb more heat from polar 24-hour sunlight conditions. This warmer Arctic will increase coastal permafrost thaw, adding more carbon to the atmosphere and increasing coastal erosion; speed Greenland Ice Sheet melt and resulting sea-level rise; and have unpredictable and potentially extreme impacts on mid- atitude weather patterns… Warmer waters also mean that any recovery of sea ice may take many decades, even with a subsequent return to lower atmospheric temperatures, because the ocean will hold that heat far longer. While some economic analysts see Arctic sea ice loss as a positive due to greater regional economic potential, the extreme levels of loss and damage and increased adaptation needs would almost certainly greatly eclipse any temporary economic gains, even by Arctic nations themselves.
1.5°C Consistent Pathways: Studies consistently indicate that Arctic sea ice will still melt almost completely some summers even at 1.5°C, but not each year and only for a brief period (days to a few weeks) when it does. Reducing the frequency of ice-free conditions will greatly decrease impacts and feedbacks both in the Arctic and throughout the planet, decreasing adaptation burdens, though still with some impacts tipping into loss and damage, especially for Arctic Indigenous and coastal communities. “Very low” emissions (SSP1-1.6, which peaks at 1.6°C) may lead to some recovery of sea ice at both poles by 2100, when temperatures begin to decline below 1.4°C.
Current rise in CO2 levels continues (3–3.5°C by 2100): If CO2 concentrations continue to grow in the atmosphere at today’s pace, which has not decreased despite current pledges, global temperatures will reach at least 3°C by the end of this century. At such high temperatures, the Arctic Ocean will be ice-free for nearly 180 days each year, leading to enhanced Arctic warming, increased permafrost degradation, increased Greenland Ice Sheet melt and weather extremes. – p37
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.
