Scientific evidence

Scientific evidence
According to the Australian Academy of Science, climate science is supported by extensive studies based on four main lines of evidence:
1) Physical principles established more than a century ago tell us that greenhouse gases, such as carbon dioxide (CO2), trap heat and keep the planet warmer than it would otherwise be. Increasing greenhouse gas levels raise the temperature of the Earth’s surface.
2) The record of the distant past (millions of years) tells us that we cannot take a stable climate for granted. Climate has varied greatly through the Earth’s history. It has, for example, gone through 10 major ice age cycles over approximately the past million years. The past few thousand years have been unusually stable. Together with our understanding of physical principles, evidence from the past shows that climate can be sensitive to small external influences.
3) Measurements from the recent past (the last 100 years) tell us that the Earth’s surface is warming along with rising levels of greenhouse gases from human activities, and that this warming is leading to other environmental changes. Although climate varies from year to year and decade to decade, the overall upward trend of average global temperature over the last century is clear.
4) Climate models, together with physical principles and knowledge of past variations, tell us that, unless greenhouse gas emissions are reduced and greenhouse gas concentrations in the atmosphere are stabilised, global warming will continue.

Natural Climate Variability

The Earth's climate has exhibited marked natural variation, with time scales varying from many millions of years down to a few years. During periods of a few years up to a decade, fluctuations in …

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Enhanced Greenhouse Effect

Certain atmospheric gases trap the sun's heat that would otherwise escape into Outer Space.These gases are called greenhouse gases because they act like the enclosure of a garden greenhouse, which …

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