are being affected by regional climate changes, particularly temperature increases." Observations Some observed changes have been associated with climate change at varying levels of confidence. With a high confidence (about an 8 in 10 chance to be correct) WGII asserts that climate change has resulted in: More and larger glacial lakes. Increasing ground instability in permafrost regions. Increasing rock avalanches in mountain regions. Changes in some Arctic and Antarctic ecosystems. Increased run-off and earlier spring peak discharge in many glacier and snow-fed rivers. Changes affecting algae, plankton, fish and zooplankton because rising water temperatures and changes in: ice cover salinity oxygen levels water circulation With a very high confidence (about a 9 in 10 chance to be correct) WGII asserts that climate change is affecting terrestrial biological systems in that: Spring events such as the unfolding of leaves, laying of eggs, and migration are happening earlier. There are poleward and upward (to higher altitude) shifts in ranges of plant and animal species. WGII also states that the ocean has become more acidic because it has absorbed human-caused carbon dioxide. Ocean pH has dropped by 0.1, but how this affects marine life is not documented. Attribution of changes WGII acknowledges some of the difficulties of attributing specific changes to human-caused global warming, stating that "Limitations and gaps prevent more complete attribution of the causes of observed system responses to anthropogenic warming." but found that the agreement between observed and projected changes was "Nevertheless ... sufficient to conclude with high confidence that anthropogenic warming over the last three decades has had a discernible influence on many physical and biological systems." Projections WGII describes some of what might be expected in the coming century, based on studies and model projections. Fresh water It is projected with high confidence that: Dry regions are projected to get drier, and wet regions are projected to get wetter: "By mid-century, annual average river runoff and water availability are projected to increase by 10–40% at high latitudes and in some wet tropical areas, and decrease by 10–30% over some dry regions at mid-latitudes and in the dry tropics..." Drought-affected areas will become larger. Heavy precipitation events are very likely to become more common and will increase flood risk. Water supplies stored in glaciers and snow cover will be reduced over the course of the century. Ecosystems It is projected with high confidence that: The resilience of many ecosystems