It is more and more evident dat humans are to be blamed for global warming. Hereunder a summary of statements from a arcticle which appeared
in Scientific American.
Scientists are confident that humans have interfered with the climate and that further human-induced climate change is on the way.
The principal driver of recent climate change is greenhouse gas emissions from human activities, primarily the burning of fossil fuels.
The report of the Intergovernmental Panel on Climate Change places the probability that global warming has been caused by human activities at greater than 90 percent.
The previous report, published in 2001, put the probability at higher than 66 percent.
Altough further changes in the world's climate are now inevitable, the future,particularly in the longer term, remains largely in our hands -the magnitude of expected change depends
on what humans choose to do about greenhouse gas emissions.
Concentrations of carbon dioxide in the atmosphere today are roughly 35 percent above preindustrial levels.
The extent of Artic sea ice has shrunk substantially.
Eleven op the past 12 years are the warmest since reliable records began around 1850.
Models using only natural forcings are unable to explain the observed global warming since the mid-20th century, weheras they can do so when they include anthropohenic factors in addition to natural ones.
Two patterns provide a fingerprint of human influence:
- There is greater warming over land than ocean and greater warming at the surface of the sea than in deeper layers. This pattern is consistent with greenhouse gasinduced warming by the overlying atmosphere.
- A second pattern of change is that while the troposphere (the lower region of the atmosphere) has warmed, the stratosphere, just above it, has cooled. If solar changes provided the dominant forcing, warming would be expected in both atmospheric layers.
The observed contrast, however,is just that expected from the combination of greenhouse gas increases and stratospheric ozone decreases.
The best estimates of the increase in global temperatures in the 21st Century range from 1.8 to 4.0 degrees C for the various emission scenarios, with higher emissions leading to higher temperatures.
The estimates of the rise in sea level during the 21st century range from about 30 to 40 centimeters, again depending on emissions. The possibility of significant larger rises cannot be excluded.
All this emphasizes the importance of improving energy efficiency in buildings and vehicles, shifting to renewable energy sources and saving forests as "carbon sinks".
Here are some graphics of prove of global warming attributed by human activities:
Greenhouse Gases: The Major Forcings
Human-induced Temperature Change
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