43
O.W. Van Auken and J.K. Bush, Invasion of Woody Legumes, SpringerBriefs in Ecology 4,
DOI 10.1007/978-1-4614-7199-8_7, © Springer Science+Business Media New York 2013
The climate of the Earth has been changing ever since the Earth has had an atmosphere. Sometimes the changes are dramatic over relatively short time intervals, and
other times the changes have been minor with long periods of relative stability.
These global climate changes continue today. It is warmer today than it has been in
the recent past, and the Earth is expected to get even warmer. The cause of the recent
rise in temperature is the elevated level of CO 2 in the atmosphere (Mackenzie 2003 ).
The expected increased warming of the Earth is not a new phenomenon, it has happened before. An example occurred approximately 56 million years ago, at the end
of the Paleocene and the beginning of the Eocene. The Earth was much warmer
compared to today, and it was about to get warmer during this Paleocene–Eocene
thermal maximum (Kunzig and Block 2011 ). The warming event was triggered by
a massive release of carbon, probably CO 2 or methane. The duration of high atmospheric carbon levels and high temperatures at that time is thought to be about
150,000 years, the time it took to reabsorb the carbon that had been released into the
atmosphere. The amount of carbon released into the atmosphere at that time is estimated to be about as much as could be released in the near future if all of the stored
fossil fuel was burned by man.
More recently, during the past 2 million years, throughout the Pleistocene, the
climate of the Earth was mostly cooler than today (McDowell et al. 1995 ; Van
Devender 1995 ; Martin 1999 ). There were probably 15–20 glacial periods during
that time with associated interglacials (Imbrie and Imbrie 1979 ). The interglacials
were 10,000–20,000 years long and the glacials about ten times longer. The present
warmer period or interglacial started about 12,500 years ago and is projected to last
much longer than most of the previous interglacials, perhaps more than 50,000
years ( Berger and Loutre 2002 ). As temperatures warmed during the interglacials,
the glaciers melted and plant communities around the world moved, adjusted, and
changed their distributions. The reverse would be true at the start of the cooling that
would precede the glacial periods.
Chapter 7
Global Climate Change
O.W. Van Auken and J.K. Bush, Invasion of Woody Legumes, SpringerBriefs in Ecology 4,
DOI 10.1007/978-1-4614-7199-8_7, © Springer Science+Business Media New York 2013
The climate of the Earth has been changing ever since the Earth has had an atmosphere. Sometimes the changes are dramatic over relatively short time intervals, and
other times the changes have been minor with long periods of relative stability.
These global climate changes continue today. It is warmer today than it has been in
the recent past, and the Earth is expected to get even warmer. The cause of the recent
rise in temperature is the elevated level of CO 2 in the atmosphere (Mackenzie 2003 ).
The expected increased warming of the Earth is not a new phenomenon, it has happened before. An example occurred approximately 56 million years ago, at the end
of the Paleocene and the beginning of the Eocene. The Earth was much warmer
compared to today, and it was about to get warmer during this Paleocene–Eocene
thermal maximum (Kunzig and Block 2011 ). The warming event was triggered by
a massive release of carbon, probably CO 2 or methane. The duration of high atmospheric carbon levels and high temperatures at that time is thought to be about
150,000 years, the time it took to reabsorb the carbon that had been released into the
atmosphere. The amount of carbon released into the atmosphere at that time is estimated to be about as much as could be released in the near future if all of the stored
fossil fuel was burned by man.
More recently, during the past 2 million years, throughout the Pleistocene, the
climate of the Earth was mostly cooler than today (McDowell et al. 1995 ; Van
Devender 1995 ; Martin 1999 ). There were probably 15–20 glacial periods during
that time with associated interglacials (Imbrie and Imbrie 1979 ). The interglacials
were 10,000–20,000 years long and the glacials about ten times longer. The present
warmer period or interglacial started about 12,500 years ago and is projected to last
much longer than most of the previous interglacials, perhaps more than 50,000
years ( Berger and Loutre 2002 ). As temperatures warmed during the interglacials,
the glaciers melted and plant communities around the world moved, adjusted, and
changed their distributions. The reverse would be true at the start of the cooling that
would precede the glacial periods.
Chapter 7
Global Climate Change