The Earth has had much larger variations in its climate in the past, this argument goes, so why worry now? Over its 4 billion year history, the Earth has experienced large variations in climate caused by natural forces. For the past 1.3 million years, the Earth has been in an ice age cycle, with periods of cold having extensive glaciation alternating with warmer "interglacial periods". We are currently in a relatively warm interglacial period.
During most of its history, the Earth was much warmer than today. A good example is the Cretaceous era, during the time when dinosaurs were at their peak. (The film, Jurassic Park, was named for the era which came before the Cretaceous, but the title was picked for sales appeal, not accuracy.) A map of the world during this age is shown above.
During the Cretaceous era, the average global temperature was 5 degrees Celsius higher than present. This is 9 degrees Fahrenheit, a very large difference in the average temperature compared to the present era. There were no ice caps at either pole, and few glaciers anywhere. The carbon dioxide level in the atmosphere was about four times higher than today, its greenhouse effect being one of the reasons the high global temperature was maintained. The sea level was, incredibly, more than 200 meters (665 feet) higher than today.
Overall, this may sound like a relatively hospitable climate, and indeed we may be heading in that direction. However, as discussed in later sections, any transition to such a warmer climate will create a lot of difficulty through changes in local climate and weather during the process.
In this section we consider only the rise in sea level that accompanies global warming. This rise is due to the melting of ice that is located on land, plus expansion of the ocean due to the increase in temperature. As an example, the map above illustrates what would happen in the eastern United States with a 100 meter rise in sea level. While this is only half of the sea level change from the present age compared to the Cretaceous, it would take many generations to reach a change of this magnitude. This map is offered as an illustration of the maximum changes in sea level possible for our planet, not the most likely immediate result.
The map shows that, during such a warming process, the U.S. would lose most of the east coast cities, all of Florida and much of Texas and Louisiana. The effect of the loss of farm land in these areas would have even more dire consequences because of the loss of most of the central valley in California, as well as low-lying agricultural areas around the world.
In comparison, the sea level rise actually expected during the present century is about a meter. The sea has already risen 20 cm. However, even this small rise in sea level, coupled with an expected increase in storm activity, is predicted to lead to disastrous consequences for many low-lying areas in the world.
In sum: It might be nice to live in a warmer world, but the consequences during the warming-up period are predicted to be severe, affecting all of the people in the world one way or another.
The fact that the Earth has gone through climate changes before does not in any way reduce the damage that such a change will do to our civilization and other life on our planet now.
General effects will include catastrophic shifts in climate, with extensive disruptions of food and water supplies, accompanied by resulting political instability. Those in coastal areas will suffer the most, and many of the world's oldest and grandest cities, as well as its agricultural areas, will have to be abandoned or extensively modified. Extreme weather of all kinds is forecast, causing damage by floods or droughts, etc. These effects are detailed in subsequent sections.
During most of its history, the Earth was much warmer than today. A good example is the Cretaceous era, during the time when dinosaurs were at their peak. (The film, Jurassic Park, was named for the era which came before the Cretaceous, but the title was picked for sales appeal, not accuracy.) A map of the world during this age is shown above.
During the Cretaceous era, the average global temperature was 5 degrees Celsius higher than present. This is 9 degrees Fahrenheit, a very large difference in the average temperature compared to the present era. There were no ice caps at either pole, and few glaciers anywhere. The carbon dioxide level in the atmosphere was about four times higher than today, its greenhouse effect being one of the reasons the high global temperature was maintained. The sea level was, incredibly, more than 200 meters (665 feet) higher than today.
Overall, this may sound like a relatively hospitable climate, and indeed we may be heading in that direction. However, as discussed in later sections, any transition to such a warmer climate will create a lot of difficulty through changes in local climate and weather during the process.
In this section we consider only the rise in sea level that accompanies global warming. This rise is due to the melting of ice that is located on land, plus expansion of the ocean due to the increase in temperature. As an example, the map above illustrates what would happen in the eastern United States with a 100 meter rise in sea level. While this is only half of the sea level change from the present age compared to the Cretaceous, it would take many generations to reach a change of this magnitude. This map is offered as an illustration of the maximum changes in sea level possible for our planet, not the most likely immediate result.The map shows that, during such a warming process, the U.S. would lose most of the east coast cities, all of Florida and much of Texas and Louisiana. The effect of the loss of farm land in these areas would have even more dire consequences because of the loss of most of the central valley in California, as well as low-lying agricultural areas around the world.
In comparison, the sea level rise actually expected during the present century is about a meter. The sea has already risen 20 cm. However, even this small rise in sea level, coupled with an expected increase in storm activity, is predicted to lead to disastrous consequences for many low-lying areas in the world.
In sum: It might be nice to live in a warmer world, but the consequences during the warming-up period are predicted to be severe, affecting all of the people in the world one way or another.
The fact that the Earth has gone through climate changes before does not in any way reduce the damage that such a change will do to our civilization and other life on our planet now.
General effects will include catastrophic shifts in climate, with extensive disruptions of food and water supplies, accompanied by resulting political instability. Those in coastal areas will suffer the most, and many of the world's oldest and grandest cities, as well as its agricultural areas, will have to be abandoned or extensively modified. Extreme weather of all kinds is forecast, causing damage by floods or droughts, etc. These effects are detailed in subsequent sections.
DETAILS
The maps were modified from The Geology of the Prehistoric World, and from 100-meter-rise maps.
This treads so lightly on the subject as to be useless. You completely ignore the well documented Roman warming period and the Medieval Warming Period that are well documented and were actually quite prosperous times for humanity. This is extremely well documented and yet you choose to ignore that. I wonder why? Could it be that it negates your pre concieved ideas? Could it be that in point of fact warming periods are proven to be beneficial to humans and indeed to most life on the planet?
ReplyDeletePlease show me one period in the paleo climate record when warmth was bad. Just one please. I can show you dozens when the planet was a iceberg with the attendant mass die offs of tens of thousands of species.