But the goal isn't just scientific exploration . . . it's also about extending the range of human habitat out from Earth into the solar system as we go forward in time. . . . In the long run a single-planet species will not survive. We have ample evidence of that . . . [Species have] been wiped out in mass extinctions on an average of every 30 million years.
Meanwhile . . .
Floods, storms, and droughts. Melting polar ice, shrinking glaciers, oceans turning to acid. Scientists from the fields of glaciology, biology, meteorology, oceanography, and ecology reported seeing a dramatic rise over the last 50 years of all the indicators of climate change: increase in average world temperatures, extreme weather events, in the levels of CO2 and other greenhouse gases, and in the level of the oceans.
[. . .]
Quite a few climate "skeptics", fossil fuel executives, and members of the Bush administration are still denying that there is such a thing as human-caused global warming. Many of them claim that the sun has just grown hotter. However, a warmer sun would have heated the stratosphere as well. In contrast, the stratosphere is cooling -- suggesting a blanket of greenhouse gases that prevents the earth’s heat from radiating back into space.