Within the next fifty years the US may experience shifting and changing length of the seasons, changes in vegetation including habitat and diversity, changes in precipitation intensity and distribution, a rise in sea-level, an increase in storm intensity and an increase in erosion events. Shifting seasons The principle sources for this idea were: Global Warming in the Temperate Zone, Geography Chapter 2, IPCC Fourth Assessment Report: Summary for Policy Makers, Alaska Survey (Us Global Change Research Program) Why? As global warming effects advance, colder seasons become milder and of shorter duration.
“Climate … refers to the annual pattern of atmospheric conditions in a place (Lew 2004). “ Since the seas change temperature more slowly than land, an increase in temperature of the sea would maintain warmer patterns for longer periods of time Impact on Physical Geography “Throughout the temperate zone, changes are being recorded in where and when plants bloom and thrive. (Global Warming in Temperate Zone 2007)” Another effect is that as the temperature rises, the altitudinal zonation normally present (Lew 2004) becomes attenuated.
In some areas, the top zones are disappearing, the temperature variations no longer dip far enough to maintain snow caps, glaciers or other physical attributes wildlife depend upon (. Global Warming in Temperate Zone 2007). Impact on Human Geography Changes in seasonality have not yet had much affect upon the lower United States human geography. Change in seasonality has had profound impact upon populations in Alaska and Canada. “[The Inuit’s] winter hunting and fishing is limited severely by loss of ice (Global Warming in the Arctic 2007). ”
Seasonal use of Ice roads, loss of sea-ice and lengthening summers all will have a profound impact on trade and national defense ( Climate Change: “Alaska” 2000). According to the IPCC report there is little that can be done to immediately reverse this trend as temperatures will continue to increase on inertia of the GHGs already in the atmosphere (Alley 2007) . Changing vegetation and Ecology The principle sources for this idea were: Global Warming in the Temperate Zone, Geography Chapter 2, IPCC Fourth Assessment Report: Summary for Policy Makers, Alaska Survey (Us Global Change Research Program)
Why? The changes in seasonality and accompanying changes in temperature constitute changes in climate (Lew 2004). Plant organisms and their distributions are usually sensitive to climate changes. Impact on Physical Geography “Climate has a direct impact on the biogeographic distribution of the natural vegetation in a region (Lew 2004). ” Observed changes in altitudinal zonation are expected to accelerate if temperatures continue to rise rapidly (Global Warming: Temperate Zone 2007). Impact on Human Geography
This effect is not likely to have an immediate impact on humans, though there may be some benefit from a longer growing season and perhaps a larger farmable area. Changes in Precipitation The principle sources for this idea were: Geography Chapter 2, IPCC Fourth Assessment Report: Summary for Policy Makers, Regional Overview (Us Global Change Research Program) Why? Warmer air can carry more moisture. As temperature rises it increases the vapor pressure of water and causes increased evaporation. When precipitation occurs it is likely to be more intense, dumping more water in less time than would normally be the case.
Impact on Physical Geography “Precipitation is very likely to continue to increase on average, especially in middle and high latitudes… in the form of heavy downpours. (US Global Change, “Water overview” 2000). “ Combined with seasonality, this means that some areas will become wetter and stay wetter longer than normal. Impact on Human Geography The resulting conditions may yield increased productivity, pest populations and disease. Introduce competition for water as the distribution and rates of precipitation change (US Global Change, “Water overview” 2000).
Changes will very likely exaggerate conflicts in regions where fresh water is reduced by increasing evaporation and changes in precipitation (US Global Change, “Water overview” 2000). Sea Level changes The principle sources for this idea were: Geography Chapter 2, IPCC report, and Global Warming in The Artic, Rising Sea Levels Why? Sea level changes are occurring from increasing mean temperatures. The types of sea level rise include volume increases due to thermal expansion, increasing output from rivers due to increased precipitation, and increased outflow from melting glacier and icecap reserves.
Impact on Physical Geography Loss of shoreline from movement of sea, submergence of low lying islands loss of wetlands and delta areas due to increased salinity in mixed water environment. Impact on Human Geography Should ice cap melting experience a surge it is possible for a rapid increase in sea-levels of 4-20 feet to occur over a short time. A rise of that size would inundate the cities forcing many to migrate away and shutting down important commercial centers, possibly permanently.
Damage could by mitigated by building dikes, tidal dams and changes to building codes requiring use of higher situated building sites, most of these protective measures are not permanent solutions. Storm intensity increases The principle sources for this idea were: Geography Chapter 2, IPCC Fourth Assessment Report: Summary for Policy Makers, Regional Overview (Us Global Change Research Program) Why? This is related to the causes for increased precipitation, the oceans get warmer, which makes more evaporative pressure.
Storms, such as hurricanes forming over water will gather more flow more quickly than they would ordinarily. The storms develop higher winds (larger volume of air is ready to enter convection) and increases in precipitation (more warm moist air, carrying more moisture than normal). Impact on Physical Geography Storms such as Hurricanes can have a profound impact on the coastal environment. Physically destroying plants, contributing to landslides, and flooding, stronger storms can change the landscape quickly. Impact on Human Geography The Katrina disaster provided some idea of the impact of super-storms.
A city was virtually destroyed. These storms will prompt more frequent short term migrations to avoid them. Direct prevention is not probable, but sensible preparation and pre-planned evacuation can go far to mitigate impact upon populations. Still long term migrations are bound to occur due to stresses on the job market, infrastructure, and availability of resources. Erosion Events The principle sources for this idea were: Global Warming in the Temperate Zone, Geography Chapter 2, IPCC Fourth Assessment Report, Rising Sea Levels Why?
Increased precipitation, higher tides, and stronger storm events translate to greater land-erosion events through mudslide, landslide, torrential run-off, and storm-surge. Impact on Physical Geography Combined, these effects will decrease the available coastal area, sweep away or bury some areas. River deltas may expand but existing habitat will be washed away as the river retreats inland with the sea following. Impact on Human Geography Perhaps the most immediate of the effects of global warming, the changes in weather patterns have already forced changes in the Carolinas, and in Galveston, and Brazoria.
Stronger currents, higher tides have encroached on property and subsidence has forced many homes to be abandoned. This may become more widespread and more coastal settlements will have to move. Some rebuilding and storm wall can be built, but the problems are long term and may not have permanent solutions beyond migration
References: Alley, Richard et al. (2007). IPCC WGI Fourth Assessment Report: Summary for Policy Makers. Retrieved February 2, 2007 from Intergovernmental Panel on Climate Change Website: http://ipcc-wg1. ucar. edu/wg1/docs/WG1AR4_SPM_PlenaryApproved. pdf