Since ice shelves already displace water, the loss will not add to rising ocean levels. But melting tundra at the northern end of the planet could have a another truly devastating global effect . In Alaska, most of which is covered by permafrost, permanently frozen tundra soil, roads and other human structures are collapsing as permafrost melts. Regular seasonal thaw is penetrating deeper in recent years. While this is inconvenient and costly for Alaska, it also raises fears that greenhouse gases locked in permafrost will be released.
Tundra globally holds carbon equal to one-third of that in the atmosphere.
In some years, the tundra is adding as much or more carbon to the atmosphere than it removes. A globally warmed atmosphere is expected to cause more evaporation, making for more deluges and flooding some places, and worse droughts in others. Beginning around 1980, sections of the U.S., Europe, Africa and Asia, indeed began to experience more dry spells, while parts of the U.S. and Europe have become much wetter. More evidence comes from the National Climatic Data Center, which scrutinized U.S. weather records for the last 80 years to track extreme precipitation events that are expected to increase under global warming. NCDC discovered that wild weather has been surging since the late 1970s.