The danger is that global warming
may become self-sustaining, if it has
not done so already. The melting of
the Arctic and Antarctic ice caps
reduces the fraction of solar energy
reflected back into space, and so
increases the temperature further.
Climate change may kill off the
Amazon and other rain forests, and so
eliminate once one of the main ways
in which carbon dioxide is removed
from the atmosphere. The rise in sea
temperature may trigger the release
of large quantities of carbon dioxide,
trapped as hydrides on the ocean
floor. Both these phenomena would
increase the greenhouse effect, and so
global warming further. We have to
reverse global warming urgently, if we
still can.
Professor Stephen Hawking
ning.com