Impacts and adaptation

The potential impacts of climate change may vary in scale and ramifications dependent upon the geographical region, the extent of human development, and the vision of community and resource managers to plan for a changing future. Temperature changes may have greater influences poleward than at the equator. Extreme storm events may increase in intensity and frequency in many regions. Regions may experience more extreme periods of flooding or drought or both. Sea level changes may exacerbate these conditions. In coastal areas already at or below sea level or experiencing subsidence or compaction of land masses, the inundation will accelerate. Changes in ocean currents and upwellings may further augment temperature impacts as some coasts lose the moderating influences of coastal currents and coastal economies are deprived of deep ocean nutrients. Many natural areas, particularly poleward, may become uninhabitable for some cold-tolerant organisms who have nowhere to which they may retreat, but, more habitable for some species including humans. Migration routes in rivers and tributaries that drain into coastal waters allow passage of anadromous species. Passage may be blocked or severely constrained because of changing hydrogeological events associated with climate change and complicated by the growth and development of human society and multi-uses applied to water bodies. Fresh water diversions of tributaries to meet the growing agricultural and industrial needs, may exacerbate the effects of climate change on coastal uses and habitat. For instance, saltwater intrusions may rapidly change habitat structure and composition and adversely impact coastal and riverine freshwater domestic and industrial users. In the polar regions, passages, totally or partially icebound much of the year, may be more open to organisms moving with physical changes in their habitat.

In the 2007 IPCC the rate of sea level rise is much reduced from the prior estimates, but the sea has been rising since the last glaciation, some 10,000 years ago and will continue to do so for thousands more years, whether or not the planet is warming. Warming should lead to an acceleration of the rise, and there is some evidence this is occuring.

The following items are from the Second IPCC Impact Assessment and are the consistent with the scenarios in the most recent warming projections .

• Temperature changes will cause geographical shifts in biota and changes in biodiversity, and in polar regions the extinction of some species and proliferation of others.
• A temperature rise in high latitudes should increase the duration of the growing period and the productivity of these regions.
• Increased coral bleaching will occur as a result of a predicted 2�C increase in average global atmospheric temperature by 2050.
• The Northwest Passage and Northern Sea Route of Russia likely will be opened for routine shipping.
• Sea-level changes will occur with regional variations.
• Changes in coastal pollutants will occur with changes in precipitation and runoff.
• Changes in circulation and vertical mixing will influence nutrient availability and primary productivity, affecting the efficiency of carbon dioxide uptake by the oceans.
• The oceans' uptake and storage capacity for greenhouse gases will be affected by changes in nutrient availability resulting from other changes in precipitation, runoff, and atmospheric deposition.
• Freshwater influx from movements and melting of sea ice or ice sheets may lead to a weakening of the global thermohaline circulation, causing unpredictable instabilities in the climate system.
• Reduced yields of desirable fish species will occur if primary productivity decreases.
• Marine mineral extraction, except for petroleum hydrocarbons and the marine pharmaceutical and biotechnological industries, is insensitive to global climate change. (Source)