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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. 1).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. 2 & 3)
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Image: Nathan Kurtz / NASA
As the climate warms, evaporation dries out vegetation, making it more prone to fires, something made all too clear in the 2025 Los Angeles fires. This triggers a range of positive (warming) feedback effects, depending on where the fires are located. There has been an explosive growth of forest fires globally, in areas that have rarely experienced them. Fires are becoming so large that entire ecosystems are being destroyed, unable to recover because temperatures are now too high to support their recovery. Every year, the wildfire season in the Northern Hemisphere (Alaska, Canada, and Russia) begins earlier, ends later, and is more intense.
Another feedback effect is soot or ‘black carbon‘ that falls on ice as far away as Greenland (Fig. 4) reducing the albedo and enhancing surface melting, which accelerates the disintegration of outlet glaciers that hold back the massive Greenland ice sheet, leading to increasing meltwater, accelerating sea level rise. Large volumes of freshwater melting is also changing ocean currents with multiple profound effects around the globe.
In addition to losing forests, fires in boreal regions are threatening to turn peat, which had once been a carbon sink, into a major source of atmospheric methane and carbon dioxide. The peat in this region is largely permafrost, but that’s now melting at an alarming rate, both from atmospheric warming and from increasingly uncontrollable forest fires melting the upper layers of the soil.
Climate warming and drying has led to more severe and frequent forest fires, which threaten to shift the carbon balance of the boreal ecosystem from net accumulation to net loss, resulting in a positive climate feedback… This implies a shift to a domain of carbon cycling in which these forests become a net source—instead of a sink—of carbon to the atmosphere over consecutive fires. – Walker et al, 2019 (Video 1)
The entire Canadian Boreal contains 307 billion tonnes of carbon…as much carbon as the world emits in 36 years. – Anthony Swift, Natural Resources Defense Council, Canada
According to the latest public records, the Canadian wildfires of 2023 have razed 18.5 million hectares of land to date – nearly triple the previous record. They released [an estimated) 2.4 billion tonnes of carbon dioxide. To put that into perspective, it’s three and a half times the annual emissions for all of Canada’s economy. – Radio NZ January 2024
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