“Our home planet is now dangerously near a ‘tipping point.’ Human-made greenhouse gases are near a level such that important climate changes may proceed mostly under the climate system’s own momentum. Impacts would include extermination of a large fraction of species on the planet, shifting of climatic zones due to an intensified hydrologic cycle with effects on freshwater availability and human health, and repeated worldwide coastal tragedies associated with storms and a continuously rising sea level..
“Civilization developed during the Holocene, a period of relatively tranquil climate now almost 12,000 years in duration. The planet has been warm enough to keep ice sheets off North America and Europe, but cool enough for ice sheets on Greenland and Antarctica to be stable. Now, with rapid warming of 0.6 degrees Celsius in the past 30 years, global temperature is at its warmest level in the Holocene.
“This warming has brought us to the precipice of a great ‘tipping point.’ If we go over the edge, it will be a transition to ‘a different planet,’ an environment far outside the range that has been experienced by humanity. There will be no return within the lifetime of any generation that can be imagined, and the trip will exterminate a large fraction of species on the planet.
“The crystallizing scientific story reveals an imminent planetary emergency. We are at a planetary tipping point. We must move onto a new energy direction within a decade to have a good chance to avoid setting in motion unstoppable climate change with irreversible effects.
“We live in a democracy and policies represent our collective will. We cannot blame others. If we allow the planet to pass tipping points…. it will be hard to explain our role to our children. We cannot claim…..that ‘we did not know.'”
NASA Climate Scientist, 2007