Short answers, pulled from the story.
Ice-albedo feedback is a self-reinforcing climate process in which changes to ice cover alter the surface reflectivity of a planet, accelerating either warming or cooling. Ice reflects far more solar energy than open water or land; when ice melts, the darker surface absorbs more heat, which melts more ice. Conversely, growing ice cover reflects more energy, cools the planet, and encourages further ice formation.
In 1969, Mikhail Ivanovich Budyko of the USSR and William D. Sellers of the United States independently published the first energy-balance climate models demonstrating that ice reflectivity had a substantial impact on Earth's climate. By 1975, Syukuro Manabe and Richard T. Wetherald had incorporated what they called "snow cover feedback" into a general circulation model measuring the effects of doubling atmospheric CO2.
Since continuous satellite readings of Arctic sea ice began in 1979, the Arctic has warmed nearly four times faster than the global average, a phenomenon known as Arctic amplification. Modelling studies show this strong amplification largely disappears when simulated sea ice cover is held constant, confirming that ice-albedo feedback is a primary driver.
The combined warming impact of Arctic and Antarctic sea ice decline between 1992 and 2018 is equivalent to about 10% of all anthropogenic greenhouse gas emissions over the same period. Arctic sea ice decline from 1979 to 2011 alone produced an estimated 0.21 watts per square meter of radiative forcing, comparable to the total 2019 radiative forcing from nitrous oxide.
In 2023, Antarctica's sea ice reached its lowest extent in 45 years of satellite records. February's summer minimum was 38% below the 1981-2000 climatological mean, and the September winter maximum broke the previous record by more than one million square kilometers. The record albedo lows contributed approximately 0.22 plus or minus 0.04 K to an unexplained 0.2 K gap in global temperatures that year, beyond what anthropogenic warming and El Nino could account for.
Under all climate change scenarios, a near-complete loss of Arctic summer sea ice in September is projected at least once before 2050. Under the scenario of continually accelerating greenhouse gas emissions, the first ice-free September is expected around 2035. A 2018 paper estimated that at 3 degrees C of warming, such events would occur roughly once every 1.5 years.
The Siachen Glacier in the Karakoram range has been a military zone between India and Pakistan since 1984. Researchers report it has retreated by several kilometers since then, driven in part by black carbon soot from kerosene use and by heat-trapping debris structures called "dirt cones" formed from discarded military waste. Both lower the glacier's albedo, causing it to absorb more solar radiation and melt faster.