01-12-2019, 01:23 AM
(This post was last modified: 01-12-2019, 01:23 AM by Alan V.)
Climate Change
Climate Change
Projected sea level rise
The melting of the Arctic sea ice will not add to sea level rise because floating sea ice already displaces its own weight in seawater. However, its reduced albedo will result in melting ice sheets elsewhere, which will add to sea level rise.
All of the non-ice sheet ice will add less than a meter to the sea level. Thermal expansion will be less than 1 to 2 meters in the next 1000 years if temperatures stay below a 5̊C increase. Another foot of sea level rise is projected by 2100 due to thermal expansion alone. Even current CO₂ levels could lead to 2 meters of sea level rise by 2100.
The complete melting of the Greenland ice sheet would add about 7 meters, or 23 feet to sea levels. The complete melting of the West Antarctic ice sheet would add about 5 meters, or 16 feet. Since the latter sits mostly on the sea bed, it is especially vulnerable to warming ocean waters. The East Antarctica ice sheet would add about 60 meters, or 197 feet, but is much less likely to melt significantly in the short run.
Sea levels will continue to rise and the rate will continue to accelerate. Even with present concentrations of CO₂, both Miami and New Orleans will be flooded by the ocean. Other cities may be able to build effective sea walls at great expense, but most coastal residents will be forced to retreat in the future. Sea levels will likely continue to rise until 2300, and an extra 8 inches of sea level rise is likely for every 5-year delay in peaking our emissions. Presently 275 million people live in areas which would be committed to flooding at 3̊C of warming. Land subsidence and gravitational effects of mass ice loss would likely result in an additional several feet of sea level rise along the Gulf and Atlantic coasts, above the global average.
If we burn all the known reserves of fossil fuels, the ice sheets may melt entirely over the long run. That would submerge all of the coastal cities in the world. Hundreds of millions of people would become climate change refugees. The economic losses would be incalculable and continuing. If the earth was completely ice free, the sea level would rise around 75 meters, or about 250 feet higher. Of course, such melting would likely take centuries.
Sea level rise by 2100 may average between 3 to 6 feet. Seas will continue to rise at 1 foot per decade thereafter. At 3 feet of sea level rise, a third of southern Florida will vanish. At 6 feet, a half will vanish. According to the Bruun Rule, 1 foot of sea level rise equals 100 to 200 feet of shoreline retreat.
Worst-case scenarios
Because of positive feedbacks, 3̊C of warming will lead to 4̊C, which will lead to 5̊C. The ocean’s conveyor-belt circulation could shut down arbitrarily. Methane from ocean seafloor hydrates could be released catastrophically.
Rising global temperatures, melting ice sheets and glaciers, rising sea levels, changing precipitation patterns, and more extreme weather events will all intensify ecological and political instabilities. The results will be water and food shortages, pandemic diseases, disputes over climate refugees and resources, poverty, hunger, and conflict.
The International Organization for Migration projects that there will likely be about 200 million climate refugees by 2050. Some regions of North Africa and the Middle East could become uninhabitable during summer months, unless people take shelter underground or in air-conditioned spaces.
To highlight a few of the more disastrous possibilities, if the earth’s average temperature rises above the preindustrial level by between 2̊C and 4̊C, we can expect a major loss of tropical rainforests and coral reefs, a huge number of species committed to extinction, and large impacts on agriculture, water resources, and human health. The Amazon rainforest may collapse and the land turn to savanna. Between 4̊C and 5̊C, we risk making large parts of the planet’s current arable and populated land in the present tropics virtually uninhabitable for much of the year for hundreds of years to come, and 50% of species will likely be committed to extinction. Between 5̊C and 6̊C, the Greenland and West Antarctic ice sheets could be committed to fully melting. Anything above 6̊C of warming could alter nature and civilization as we presently know them. Such catastrophic, worst-case scenarios can’t be ruled out as impossible.
The melting of the Arctic sea ice will not add to sea level rise because floating sea ice already displaces its own weight in seawater. However, its reduced albedo will result in melting ice sheets elsewhere, which will add to sea level rise.
All of the non-ice sheet ice will add less than a meter to the sea level. Thermal expansion will be less than 1 to 2 meters in the next 1000 years if temperatures stay below a 5̊C increase. Another foot of sea level rise is projected by 2100 due to thermal expansion alone. Even current CO₂ levels could lead to 2 meters of sea level rise by 2100.
The complete melting of the Greenland ice sheet would add about 7 meters, or 23 feet to sea levels. The complete melting of the West Antarctic ice sheet would add about 5 meters, or 16 feet. Since the latter sits mostly on the sea bed, it is especially vulnerable to warming ocean waters. The East Antarctica ice sheet would add about 60 meters, or 197 feet, but is much less likely to melt significantly in the short run.
Sea levels will continue to rise and the rate will continue to accelerate. Even with present concentrations of CO₂, both Miami and New Orleans will be flooded by the ocean. Other cities may be able to build effective sea walls at great expense, but most coastal residents will be forced to retreat in the future. Sea levels will likely continue to rise until 2300, and an extra 8 inches of sea level rise is likely for every 5-year delay in peaking our emissions. Presently 275 million people live in areas which would be committed to flooding at 3̊C of warming. Land subsidence and gravitational effects of mass ice loss would likely result in an additional several feet of sea level rise along the Gulf and Atlantic coasts, above the global average.
If we burn all the known reserves of fossil fuels, the ice sheets may melt entirely over the long run. That would submerge all of the coastal cities in the world. Hundreds of millions of people would become climate change refugees. The economic losses would be incalculable and continuing. If the earth was completely ice free, the sea level would rise around 75 meters, or about 250 feet higher. Of course, such melting would likely take centuries.
Sea level rise by 2100 may average between 3 to 6 feet. Seas will continue to rise at 1 foot per decade thereafter. At 3 feet of sea level rise, a third of southern Florida will vanish. At 6 feet, a half will vanish. According to the Bruun Rule, 1 foot of sea level rise equals 100 to 200 feet of shoreline retreat.
Worst-case scenarios
Because of positive feedbacks, 3̊C of warming will lead to 4̊C, which will lead to 5̊C. The ocean’s conveyor-belt circulation could shut down arbitrarily. Methane from ocean seafloor hydrates could be released catastrophically.
Rising global temperatures, melting ice sheets and glaciers, rising sea levels, changing precipitation patterns, and more extreme weather events will all intensify ecological and political instabilities. The results will be water and food shortages, pandemic diseases, disputes over climate refugees and resources, poverty, hunger, and conflict.
The International Organization for Migration projects that there will likely be about 200 million climate refugees by 2050. Some regions of North Africa and the Middle East could become uninhabitable during summer months, unless people take shelter underground or in air-conditioned spaces.
To highlight a few of the more disastrous possibilities, if the earth’s average temperature rises above the preindustrial level by between 2̊C and 4̊C, we can expect a major loss of tropical rainforests and coral reefs, a huge number of species committed to extinction, and large impacts on agriculture, water resources, and human health. The Amazon rainforest may collapse and the land turn to savanna. Between 4̊C and 5̊C, we risk making large parts of the planet’s current arable and populated land in the present tropics virtually uninhabitable for much of the year for hundreds of years to come, and 50% of species will likely be committed to extinction. Between 5̊C and 6̊C, the Greenland and West Antarctic ice sheets could be committed to fully melting. Anything above 6̊C of warming could alter nature and civilization as we presently know them. Such catastrophic, worst-case scenarios can’t be ruled out as impossible.
