The science of man-made climate change NOT settled 257

On March 28, 2012, fifty former employees of the  National Aeronautics and Space Administration (NASA) signed a letter to Charles Bolden, NASA’s Administrator.

Here is most of it. It can be found in full at Powerline:

Dear Charlie,

We, the undersigned, respectfully request that NASA and the Goddard Institute for Space Studies (GISS) refrain from including unproven remarks in public releases and websites. We believe the claims by NASA and GISS, that man-made carbon dioxide is having a catastrophic impact on global climate change are not substantiated, especially when considering thousands of years of empirical data. With hundreds of well-known climate scientists and tens of thousands of other scientists publicly declaring their disbelief in the catastrophic forecasts, coming particularly from the GISS leadership, it is clear that the science is NOT settled.

The unbridled advocacy of CO2 being the major cause of climate change is unbecoming of NASA’s history of making an objective assessment of all available scientific data prior to making decisions or public statements.

As former NASA employees, we feel that NASA’s advocacy of an extreme position, prior to a thorough study of the possible overwhelming impact of natural climate drivers is inappropriate. We request that NASA refrain from including unproven and unsupported remarks in its future releases and websites on this subject. At risk is damage to the exemplary reputation of NASA, NASA’s current or former scientists and employees, and even the reputation of science itself. …

In particular, the “unproven remarks” are being made by James Hansen, head of NASA’s Goddard Institute for Space Studies, of whom John Hinderaker of Powerline writes:

One of the world’s four or five leading global warming alarmists is James Hansen, [who], traveling in China, denounced the United States and hailed China as the world’s “best hope” to stave off global warming. Hansen described Americans as “barbarians” with a fake democracy, and urged China’s rulers to lead a boycott of the United States in the hope that it would bring our economy to its knees.

The reputation of NASA took a hit when President Obama redefined its foremost task as “reaching out to the Muslim world”:

In a far-reaching restatement of goals for the nation’s space agency, NASA administrator Charles Bolden says President Obama has ordered him to pursue three new objectives: to “re-inspire children” to study science and math, to “expand our international relationships,” and to “reach out to the Muslim world.” Of those three goals, Bolden said in a recent interview with al-Jazeera, the mission to reach out to Muslims is “perhaps foremost,” because it will help Islamic nations “feel good” about their scientific accomplishments.

What scientific accomplishments would those be?