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In 1997, Greenpeace documented a canyon-sized crack in Antarctica's Larsen B ice shelf. In 2002, the ice shelf disintegrated. Scientists were shocked by how fast the 500 billion tonne ice sheet collapsed.
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Our world is hotter than it has been for 2000 years. If current trends continue, the global
temperature will likely climb higher than it has for two
million years. This warming is uniquely global and cannot be explained by the natural mechanisms that
explain previous warm periods in the Earth's history.
There is a broad scientific consensus that humanity is largely responsible for this change, and that choices we make today will decide
the climate of the future.
What the scientists say
There is mainstream scientific agreement on the key facts about climate change:
(1) Certain gases, such as carbon dioxide, in the atmosphere create a greenhouse effect, trapping heat and keeping the Earth warm enough to sustain life as we know it.
(2) Burning fossil fuels (coal, oil and gas) releases more carbon dioxide into the atmosphere. Although not the most potent greenhouse gas, carbon dioxide is the most significant in terms of human effects because of the large quantities emitted.
(3) Carbon dioxide concentrations in the atmosphere are now the highest in 150,000 years.
(4) Worldwide temperatures have risen between 0.5 and 0.9 degrees Celsius since 1900, higher than global trends. Ocean temperatures are also rising.
There is also widespread agreement that:"The scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action."
Joint statement by 11 national science academies to world leaders
(1) A certain amount of additional warming (about 1.3º Celsius), compared to pre-industrial levels, is probably inevitable because of emissions so far. Limiting warming to under 2° Celsius is considered vital to preventing the worst effects of climate change.
(2) If our greenhouse gas emissions are not brought under control, the speed of climate change over the next 100 years will be faster than anything known since before the dawn of civilisation.
(3) There is a very real possibility that climate feedback mechanisms will result in a sudden and irreversible climate shift. No one knows how much global warming it would take to trigger such a doomsday scenario.
