SPECIAL FEATURE
Another example comes from Southeast Asia. The iconic Angkor Wat temple complex was built in the early 12th century CE in the capital of the Khmer Empire, first as its state temple and later as a mausoleum. The kingdom reached its greatest territorial extent under King Jayavarman VII who defeated the Chams and conquered large parts of their territory (in what is now central and southern Viet Nam). But only a hundred years later the Khmer Empire was in a death spiral. What had happened? Though historians have identified a number of reasons (external threats, religious strife, internal destabilization), ecological failure and breakdown of infrastructure are seen as major catalysts. Periods of drought led to decreases in agricultural productivity and monsoon floods damaged the water infrastructure. To adapt to the growing population, trees were cut down to clear space for more rice fields. That created rain runoff carrying sediment to the canal network and damaged the system until it became inoperable. Climate change also had its hand in developments on the other side of the world: In Greenland, an island in the far North Atlantic, some 5,000 Viking settlers lived for around 500 years until the “Little Ice Age” during the early 15th century disrupted their lives. Temperatures dropped, reducing substantially the productivity of farms and making it harder to raise livestock. When attempts to use the sea as a source of food failed, the Norsemen eventually had to abandon their colony. The natural cycle of climate change is an ongoing and unavoidable part of life. When the Earth was created some 5 billion years ago the young sun was shining 30 percent weaker than it does today, writes the climatologist Dirk Notz, University of Hamburg. Nevertheless, the infant Earth was sufficiently warm to allow the existence of liquid water. That changed about 650 million years ago, when the Earth was covered in ice for many millions of years. When volcanic eruptions led to the emission of greenhouse gases, the Earth was able to warm again: Some 100 million years ago, when the dinosaurs dominated the biosphere, the average global temper- ature was about 14°C higher than today.
“Regionally, changes in climate have most likely repeatedly contributed to the disappearance of ancient cultures, but globally the development was able to continue.” Dirk Notz, Climatologist, University of Hamburg
Photo: Muratart/Shutterstock
Industrialization and the triumph of the automobile, powered by the internal combustion engine, changed the world – and further increased the burning of fossil fuels: In 1927, carbon emissions from fossil fuel burning and industry reached 1 billion tonnes per year for the first time worldwide. Despite various efforts to reverse the trend it continues: In 2006, carbon emissions from the same sources reached 8 billion tonnes per year. The consequences are clear. The Intergovernmental Panel on Climate Change (IPCC) says: “Human activities have warmed the Earth’s climate by more than 1°C since the late 19th century, and the effects on our climate are unprecedented.” An increase of 1.5°C could put between 20 and 30 percent of animal species on the fast track to extinction. If the planet warms by an average of 2°C the consequences will include a devastating loss of coral reefs, loss of habitats for many insect species and more than a third of humanity exposed to extreme heat at least once every five years, according to the Australian Climate Council. Extreme weather events, floods and droughts will threaten millions with famine, massively increasing migratory pressures. These are stark warnings and the clock is ticking. Professor Notz notes: “Climate change and disease evolution have been the wild cards of human history.” The challenge humankind is now facing was captured by the Scottish writer Robert Louis Stevenson: “Life is not a matter of holding good cards, but of playing a poor hand well.”
As climate change has always been a feature of the evolution of our planet, it is quite unusual that for the past 10,000 years climate conditions on Earth have been so stable. In fact, this stability was the precondition for the development of modern civilization: agriculture, settlements, trade, migration, communities. Professor Notz: “Regionally, changes in climate have most likely repeatedly contributed to the disappearance of ancient cultures, but globally the development was able to continue.” What is new – and today widely accepted – is the impact of humankind on climate change. Since the 1760 invention of the steam engine fired off the Industrial Revolution, ever-increasing amounts of polluting gases have been pumped into the atmosphere, triggering an unprecedented rate of warming. This has not gone unnoticed: Following scientific examinations of climate change by pioneering scientists, in 1824 the French physicist Joseph Fourier became the first to describe the Earth’s “greenhouse effect.”
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