Secretary of Energy Steven Chu announced his resignation today. He sent out a remarkable letter to Energy Department employees.

Given that he has not spoken out strongly on the climate crisis since the start of his term, his words on the subject are striking. Here are some excerpts:

The average temperature of our planet is rising, with majority of the temperature increase occurring in the last thirty years. During the three decades from 1980 to 2011, the number of violent storms, floods, droughts, heat waves, wildfires, as tabulated by the reinsurance company Munich Re, has increased more than three-fold. They also estimate that the financial losses follow a trend line that has gone from $40 billion to $170 billion dollars per year. Most of those losses were not insured, and the country suffering the largest losses by far is the United States. As the President said in his recent Inaugural Address, “some may still deny the overwhelming judgment of science, but none can avoid the devastating impact of raging fires, and crippling drought, and more powerful storms.”

The overwhelming scientific consensus is that human activity has had a significant and likely dominant role in climate change. There is also increasingly compelling evidence that the weather changes we have witnessed during this thirty year time period are due to climate change.

Virtually all of the other OECD countries, and most developing countries including China, India, Mexico, and Brazil have accepted the judgment of climate scientists.

… China now exceeds the U.S. in internal deployment of clean energy and in government investments to further develop the technologies.

… the risks we run if we don’t change our course are enormous. Prudent risk management does not equate uncertainty with inaction….

The cost of renewable energy is rapidly becoming competitive with other sources of energy, and the Department has played a significant role in accelerating the transition to affordable, accessible and sustainable energy.

Ultimately we have a moral responsibility to the most innocent victims of adverse climate change. Those who will suffer the most are the people who are the most innocent: the world’s poorest citizens and those yet to be born. There is an ancient Native American saying: “We do not inherit the land from our ancestors, we borrow it from our children.” A few short decades later, we don’t want our children to ask, “What were our parents thinking? Didn’t they care about us?”

Chu has been an excellent Secretary of Energy, overseeing a near doubling of U.S. renewable energy capacity and a huge jump in clean energy R&D. You can see a comprehensive list of what has been achieved during Chu’s term in his letter.

My main disappointment with his tenure is that after beginning with such refreshing bluntness on the threat posed by unrestricted greenhouse gas emissions — see Steven Chu on climate change (2/09): “Wake up,” America, “we’re looking at a scenario where there’s no more agriculture in California”– he was effectively muzzled by the White House.

But that was doubtless not his choice. Team Obama obviously didn’t want him or science advisor John Holdren — or anybody else, for that matter — speaking out strongly on the gravest preventable threat to modern human civilization (see “Team Obama Launched The Inane Strategy Of Downplaying Climate Change Back In March 2009“).

Chu will be missed.